Exclude testing PRs from release notes

Fixes #714

.github/release.yml

@@ -2,6 +2,7 @@ changelog:
   exclude:
     labels:
       - build
+      - testing
   categories:
     - title: What's new
       labels:

README.md

@@ -55,8 +55,9 @@ to check for typos. [See example in the documentation][strict].
 
 ### Contextualized errors
 
-When decoding errors occur, go-toml returns [`DecodeError`][decode-err]), which
+When most decoding errors occur, go-toml returns [`DecodeError`][decode-err]),
-contains a human readable contextualized version of the error. For example:
+which contains a human readable contextualized version of the error. For
+example:
 
 ```
 2| key1 = "value1"
@@ -324,6 +325,29 @@ The recommended replacement is pre-filling the struct before unmarshaling.
 
 [go-defaults]: https://github.com/mcuadros/go-defaults
 
+#### `toml.Tree` replacement
+
+This structure was the initial attempt at providing a document model for
+go-toml. It allows manipulating the structure of any document, encoding and
+decoding from their TOML representation. While a more robust feature was
+initially planned in go-toml v2, this has been ultimately [removed from
+scope][nodoc] of this library, with no plan to add it back at the moment. The
+closest equivalent at the moment would be to unmarshal into an `interface{}` and
+use type assertions and/or reflection to manipulate the arbitrary
+structure. However this would fall short of providing all of the TOML features
+such as adding comments and be specific about whitespace.
+
+
+#### `toml.Position` are not retrievable anymore
+
+The API for retrieving the position (line, column) of a specific TOML element do
+not exist anymore. This was done to minimize the amount of concepts introduced
+by the library (query path), and avoid the performance hit related to storing
+positions in the absence of a document model, for a feature that seemed to have
+little use. Errors however have gained more detailed position
+information. Position retrieval seems better fitted for a document model, which
+has been [removed from the scope][nodoc] of go-toml v2 at the moment.
+
 ### Encoding / Marshal
 
 #### Default struct fields order
@@ -359,7 +383,8 @@ fmt.Println("v2:\n" + string(b))
 ```
 
 There is no way to make v2 encoder behave like v1. A workaround could be to
-manually sort the fields alphabetically in the struct definition.
+manually sort the fields alphabetically in the struct definition, or generate
+struct types using `reflect.StructOf`.
 
 #### No indentation by default
 
@@ -407,7 +432,9 @@ fmt.Println("v2 Encoder:\n" + string(buf.Bytes()))
 
 V1 always uses double quotes (`"`) around strings and keys that cannot be
 represented bare (unquoted). V2 uses single quotes instead by default (`'`),
-unless a character cannot be represented, then falls back to double quotes.
+unless a character cannot be represented, then falls back to double quotes. As a
+result of this change, `Encoder.QuoteMapKeys` has been removed, as it is not
+useful anymore.
 
 There is no way to make v2 encoder behave like v1.
 
@@ -422,6 +449,84 @@ There is no way to make v2 encoder behave like v1.
 
 [tm]: https://golang.org/pkg/encoding/#TextMarshaler
 
+#### `Encoder.CompactComments` has been removed
+
+Emitting compact comments is now the default behavior of go-toml. This option
+is not necessary anymore.
+
+#### Struct tags have been merged
+
+V1 used to provide multiple struct tags: `comment`, `commented`, `multiline`,
+`toml`, and `omitempty`. To behave more like the standard library, v2 has merged
+`toml`, `multiline`, and `omitempty`. For example:
+
+```go
+type doc struct {
+	// v1
+	F string `toml:"field" multiline:"true" omitempty:"true"`
+	// v2
+	F string `toml:"field,multiline,omitempty"`
+}
+```
+
+Has a result, the `Encoder.SetTag*` methods have been removed, as there is just
+one tag now.
+
+
+#### `commented` tag has been removed
+
+There is no replacement for the `commented` tag. This feature would be better
+suited in a proper document model for go-toml v2, which has been [cut from
+scope][nodoc] at the moment.
+
+#### `Encoder.ArraysWithOneElementPerLine` has been renamed
+
+The new name is `Encoder.SetArraysMultiline`. The behavior should be the same.
+
+#### `Encoder.Indentation` has been renamed
+
+The new name is `Encoder.SetIndentSymbol`. The behavior should be the same.
+
+
+#### Embedded structs are tables
+
+V1 defaults to merging embedded struct fields into the embedding struct. This
+behavior was unexpected because it does not follow the standard library. To
+avoid breaking backward compatibility, the `Encoder.PromoteAnonymous` method was
+added to make the encoder behave correctly. Given backward compatibility is not
+a problem anymore, v2 does the right thing by default. There is no way to revert
+to the old behavior, and `Encoder.PromoteAnonymous` has been removed.
+
+```go
+type Embedded struct {
+	Value string `toml:"value"`
+}
+
+type Doc struct {
+	Embedded
+}
+
+d := Doc{}
+
+fmt.Println("v1:")
+b, err := v1.Marshal(d)
+fmt.Println(string(b))
+
+fmt.Println("v2:")
+b, err = v2.Marshal(d)
+fmt.Println(string(b))
+
+// Output:
+// v1:
+// value = ""
+//
+// v2:
+// [Embedded]
+// value = ''
+```
+
+[nodoc]: https://github.com/pelletier/go-toml/discussions/506#discussioncomment-1526038
+
 ## License
 
 The MIT License (MIT). Read [LICENSE](LICENSE).

cmd/tomltestgen/main.go

@@ -43,8 +43,7 @@ type testsCollection struct {
 	Count     int
 }
 
-const srcTemplate = "// +build testsuite\n\n" +
+const srcTemplate = "// Generated by tomltestgen for toml-test ref {{.Ref}} on {{.Timestamp}}\n" +
-	"// Generated by tomltestgen for toml-test ref {{.Ref}} on {{.Timestamp}}\n" +
 	"package toml_test\n" +
 	" import (\n" +
 	"	\"testing\"\n" +

decode.go

@@ -35,13 +35,22 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 		return date, newDecodeError(b, "dates are expected to have the format YYYY-MM-DD")
 	}
 
-	date.Year = parseDecimalDigits(b[0:4])
+	var err error
 
-	v := parseDecimalDigits(b[5:7])
+	date.Year, err = parseDecimalDigits(b[0:4])
+	if err != nil {
+		return LocalDate{}, err
+	}
 
-	date.Month = v
+	date.Month, err = parseDecimalDigits(b[5:7])
+	if err != nil {
+		return LocalDate{}, err
+	}
 
-	date.Day = parseDecimalDigits(b[8:10])
+	date.Day, err = parseDecimalDigits(b[8:10])
+	if err != nil {
+		return LocalDate{}, err
+	}
 
 	if !isValidDate(date.Year, date.Month, date.Day) {
 		return LocalDate{}, newDecodeError(b, "impossible date")
@@ -50,15 +59,18 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 	return date, nil
 }
 
-func parseDecimalDigits(b []byte) int {
+func parseDecimalDigits(b []byte) (int, error) {
 	v := 0
 
-	for _, c := range b {
+	for i, c := range b {
+		if c < '0' || c > '9' {
+			return 0, newDecodeError(b[i:i+1], "expected digit (0-9)")
+		}
 		v *= 10
 		v += int(c - '0')
 	}
 
-	return v
+	return v, nil
 }
 
 func parseDateTime(b []byte) (time.Time, error) {
@@ -87,13 +99,36 @@ func parseDateTime(b []byte) (time.Time, error) {
 		if len(b) != dateTimeByteLen {
 			return time.Time{}, newDecodeError(b, "invalid date-time timezone")
 		}
-		direction := 1
+		var direction int
-		if b[0] == '-' {
+		switch b[0] {
+		case '-':
 			direction = -1
+		case '+':
+			direction = +1
+		default:
+			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset character")
+		}
+
+		if b[3] != ':' {
+			return time.Time{}, newDecodeError(b[3:4], "expected a : separator")
+		}
+
+		hours, err := parseDecimalDigits(b[1:3])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if hours > 23 {
+			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset hours")
+		}
+
+		minutes, err := parseDecimalDigits(b[4:6])
+		if err != nil {
+			return time.Time{}, err
+		}
+		if minutes > 59 {
+			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset minutes")
 		}
 
-		hours := digitsToInt(b[1:3])
-		minutes := digitsToInt(b[4:6])
 		seconds := direction * (hours*3600 + minutes*60)
 		zone = time.FixedZone("", seconds)
 		b = b[dateTimeByteLen:]
@@ -159,7 +194,13 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, newDecodeError(b, "times are expected to have the format HH:MM:SS[.NNNNNN]")
 	}
 
-	t.Hour = parseDecimalDigits(b[0:2])
+	var err error
+
+	t.Hour, err = parseDecimalDigits(b[0:2])
+	if err != nil {
+		return t, nil, err
+	}
+
 	if t.Hour > 23 {
 		return t, nil, newDecodeError(b[0:2], "hour cannot be greater 23")
 	}
@@ -167,7 +208,10 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, newDecodeError(b[2:3], "expecting colon between hours and minutes")
 	}
 
-	t.Minute = parseDecimalDigits(b[3:5])
+	t.Minute, err = parseDecimalDigits(b[3:5])
+	if err != nil {
+		return t, nil, err
+	}
 	if t.Minute > 59 {
 		return t, nil, newDecodeError(b[3:5], "minutes cannot be greater 59")
 	}
@@ -175,42 +219,58 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, newDecodeError(b[5:6], "expecting colon between minutes and seconds")
 	}
 
-	t.Second = parseDecimalDigits(b[6:8])
+	t.Second, err = parseDecimalDigits(b[6:8])
-	if t.Second > 59 {
+	if err != nil {
-		return t, nil, newDecodeError(b[3:5], "seconds cannot be greater 59")
+		return t, nil, err
 	}
 
-	const minLengthWithFrac = 9
+	if t.Second > 60 {
-	if len(b) >= minLengthWithFrac && b[minLengthWithFrac-1] == '.' {
+		return t, nil, newDecodeError(b[6:8], "seconds cannot be greater 60")
+	}
+
+	b = b[8:]
+
+	if len(b) >= 1 && b[0] == '.' {
 		frac := 0
+		precision := 0
 		digits := 0
 
-		for i, c := range b[minLengthWithFrac:] {
+		for i, c := range b[1:] {
 			if !isDigit(c) {
 				if i == 0 {
-					return t, nil, newDecodeError(b[i:i+1], "need at least one digit after fraction point")
+					return t, nil, newDecodeError(b[0:1], "need at least one digit after fraction point")
 				}
-
 				break
 			}
+			digits++
 
 			const maxFracPrecision = 9
 			if i >= maxFracPrecision {
-				return t, nil, newDecodeError(b[i:i+1], "maximum precision for date time is nanosecond")
+				// go-toml allows decoding fractional seconds
+				// beyond the supported precision of 9
+				// digits. It truncates the fractional component
+				// to the supported precision and ignores the
+				// remaining digits.
+				//
+				// https://github.com/pelletier/go-toml/discussions/707
+				continue
 			}
 
 			frac *= 10
 			frac += int(c - '0')
-			digits++
+			precision++
 		}
 
-		t.Nanosecond = frac * nspow[digits]
+		if precision == 0 {
-		t.Precision = digits
+			return t, nil, newDecodeError(b[:1], "nanoseconds need at least one digit")
+		}
 
-		return t, b[9+digits:], nil
+		t.Nanosecond = frac * nspow[precision]
+		t.Precision = precision
+
+		return t, b[1+digits:], nil
 	}
-
+	return t, b, nil
-	return t, b[8:], nil
 }
 
 //nolint:cyclop
@@ -335,8 +395,17 @@ func parseIntDec(b []byte) (int64, error) {
 }
 
 func checkAndRemoveUnderscoresIntegers(b []byte) ([]byte, error) {
-	if b[0] == '_' {
+	start := 0
-		return nil, newDecodeError(b[0:1], "number cannot start with underscore")
+	if b[start] == '+' || b[start] == '-' {
+		start++
+	}
+
+	if len(b) == start {
+		return b, nil
+	}
+
+	if b[start] == '_' {
+		return nil, newDecodeError(b[start:start+1], "number cannot start with underscore")
 	}
 
 	if b[len(b)-1] == '_' {
@@ -405,6 +474,13 @@ func checkAndRemoveUnderscoresFloats(b []byte) ([]byte, error) {
 			if !before {
 				return nil, newDecodeError(b[i-1:i+1], "number must have at least one digit between underscores")
 			}
+			if i < len(b)-1 && (b[i+1] == 'e' || b[i+1] == 'E') {
+				return nil, newDecodeError(b[i+1:i+2], "cannot have underscore before exponent")
+			}
+			before = false
+		case '+', '-':
+			// signed exponents
+			cleaned = append(cleaned, c)
 			before = false
 		case 'e', 'E':
 			if i < len(b)-1 && b[i+1] == '_' {
@@ -430,7 +506,7 @@ func checkAndRemoveUnderscoresFloats(b []byte) ([]byte, error) {
 
 // isValidDate checks if a provided date is a date that exists.
 func isValidDate(year int, month int, day int) bool {
-	return day <= daysIn(month, year)
+	return month > 0 && month < 13 && day > 0 && day <= daysIn(month, year)
 }
 
 // daysBefore[m] counts the number of days in a non-leap year

errors_test.go

@@ -212,12 +212,12 @@ func ExampleDecodeError() {
 
 	fmt.Println(err)
 
-	//nolint:errorlint
+	var derr *DecodeError
-	de := err.(*DecodeError)
+	if errors.As(err, &derr) {
-	fmt.Println(de.String())
+		fmt.Println(derr.String())
-
+		row, col := derr.Position()
-	row, col := de.Position()
+		fmt.Println("error occurred at row", row, "column", col)
-	fmt.Println("error occurred at row", row, "column", col)
+	}
 	// Output:
 	// toml: number must have at least one digit between underscores
 	// 1| name = 123__456

internal/ast/ast.go

@@ -20,8 +20,8 @@ type Iterator struct {
 	node    *Node
 }
 
-// Next moves the iterator forward and returns true if points to a node, false
+// Next moves the iterator forward and returns true if points to a
-// otherwise.
+// node, false otherwise.
 func (c *Iterator) Next() bool {
 	if !c.started {
 		c.started = true
@@ -31,8 +31,8 @@ func (c *Iterator) Next() bool {
 	return c.node.Valid()
 }
 
-// IsLast returns true if the current node of the iterator is the last one.
+// IsLast returns true if the current node of the iterator is the last
-// Subsequent call to Next() will return false.
+// one.  Subsequent call to Next() will return false.
 func (c *Iterator) IsLast() bool {
 	return c.node.next == 0
 }
@@ -62,20 +62,20 @@ func (r *Root) at(idx Reference) *Node {
 	return &r.nodes[idx]
 }
 
-// Arrays have one child per element in the array.
+// Arrays have one child per element in the array.  InlineTables have
-// InlineTables have one child per key-value pair in the table.
+// one child per key-value pair in the table.  KeyValues have at least
-// KeyValues have at least two children. The first one is the value. The
+// two children. The first one is the value. The rest make a
-// rest make a potentially dotted key.
+// potentially dotted key.  Table and Array table have one child per
-// Table and Array table have one child per element of the key they
+// element of the key they represent (same as KeyValue, but without
-// represent (same as KeyValue, but without the last node being the value).
+// the last node being the value).
-// children []Node
 type Node struct {
 	Kind Kind
 	Raw  Range  // Raw bytes from the input.
-	Data []byte // Node value (could be either allocated or referencing the input).
+	Data []byte // Node value (either allocated or referencing the input).
 
-	// References to other nodes, as offsets in the backing array from this
+	// References to other nodes, as offsets in the backing array
-	// node. References can go backward, so those can be negative.
+	// from this node. References can go backward, so those can be
+	// negative.
 	next  int // 0 if last element
 	child int // 0 if no child
 }
@@ -85,8 +85,8 @@ type Range struct {
 	Length uint32
 }
 
-// Next returns a copy of the next node, or an invalid Node if there is no
+// Next returns a copy of the next node, or an invalid Node if there
-// next node.
+// is no next node.
 func (n *Node) Next() *Node {
 	if n.next == 0 {
 		return nil
@@ -96,9 +96,9 @@ func (n *Node) Next() *Node {
 	return (*Node)(danger.Stride(ptr, size, n.next))
 }
 
-// Child returns a copy of the first child node of this node. Other children
+// Child returns a copy of the first child node of this node. Other
-// can be accessed calling Next on the first child.
+// children can be accessed calling Next on the first child.  Returns
-// Returns an invalid Node if there is none.
+// an invalid Node if there is none.
 func (n *Node) Child() *Node {
 	if n.child == 0 {
 		return nil
@@ -113,10 +113,9 @@ func (n *Node) Valid() bool {
 	return n != nil
 }
 
-// Key returns the child nodes making the Key on a supported node. Panics
+// Key returns the child nodes making the Key on a supported
-// otherwise.
+// node. Panics otherwise.  They are guaranteed to be all be of the
-// They are guaranteed to be all be of the Kind Key. A simple key would return
+// Kind Key. A simple key would return just one element.
-// just one element.
 func (n *Node) Key() Iterator {
 	switch n.Kind {
 	case KeyValue:
@@ -133,10 +132,9 @@ func (n *Node) Key() Iterator {
 }
 
 // Value returns a pointer to the value node of a KeyValue.
-// Guaranteed to be non-nil.
+// Guaranteed to be non-nil.  Panics if not called on a KeyValue node,
-// Panics if not called on a KeyValue node, or if the Children are malformed.
+// or if the Children are malformed.
 func (n *Node) Value() *Node {
-	assertKind(KeyValue, *n)
 	return n.Child()
 }
 
@@ -144,9 +142,3 @@ func (n *Node) Value() *Node {
 func (n *Node) Children() Iterator {
 	return Iterator{node: n.Child()}
 }
-
-func assertKind(k Kind, n Node) {
-	if n.Kind != k {
-		panic(fmt.Errorf("method was expecting a %s, not a %s", k, n.Kind))
-	}
-}

internal/danger/typeid.go

@@ -0,0 +1,23 @@
+package danger
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// typeID is used as key in encoder and decoder caches to enable using
+// the optimize runtime.mapaccess2_fast64 function instead of the more
+// expensive lookup if we were to use reflect.Type as map key.
+//
+// typeID holds the pointer to the reflect.Type value, which is unique
+// in the program.
+//
+// https://github.com/segmentio/encoding/blob/master/json/codec.go#L59-L61
+type TypeID unsafe.Pointer
+
+func MakeTypeID(t reflect.Type) TypeID {
+	// reflect.Type has the fields:
+	// typ unsafe.Pointer
+	// ptr unsafe.Pointer
+	return TypeID((*[2]unsafe.Pointer)(unsafe.Pointer(&t))[1])
+}

internal/imported_tests/unmarshal_imported_test.go

@@ -457,35 +457,6 @@ func TestEmptytomlUnmarshal(t *testing.T) {
 	assert.Equal(t, emptyTestData, result)
 }
 
-func TestEmptyUnmarshalOmit(t *testing.T) {
-	t.Skipf("Have not figured yet if omitempty is a good idea")
-
-	type emptyMarshalTestStruct2 struct {
-		Title      string                  `toml:"title"`
-		Bool       bool                    `toml:"bool,omitempty"`
-		Int        int                     `toml:"int, omitempty"`
-		String     string                  `toml:"string,omitempty "`
-		StringList []string                `toml:"stringlist,omitempty"`
-		Ptr        *basicMarshalTestStruct `toml:"ptr,omitempty"`
-		Map        map[string]string       `toml:"map,omitempty"`
-	}
-
-	emptyTestData2 := emptyMarshalTestStruct2{
-		Title:      "Placeholder",
-		Bool:       false,
-		Int:        0,
-		String:     "",
-		StringList: []string{},
-		Ptr:        nil,
-		Map:        map[string]string{},
-	}
-
-	result := emptyMarshalTestStruct2{}
-	err := toml.Unmarshal(emptyTestToml, &result)
-	require.NoError(t, err)
-	assert.Equal(t, emptyTestData2, result)
-}
-
 type pointerMarshalTestStruct struct {
 	Str       *string
 	List      *[]string

internal/tracker/seen.go

@@ -3,6 +3,7 @@ package tracker
 import (
 	"bytes"
 	"fmt"
+	"sync"
 
 	"github.com/pelletier/go-toml/v2/internal/ast"
 )
@@ -54,63 +55,99 @@ func (k keyKind) String() string {
 type SeenTracker struct {
 	entries    []entry
 	currentIdx int
-	nextID     int
+}
+
+var pool sync.Pool
+
+func (s *SeenTracker) reset() {
+	// Always contains a root element at index 0.
+	s.currentIdx = 0
+	if len(s.entries) == 0 {
+		s.entries = make([]entry, 1, 2)
+	} else {
+		s.entries = s.entries[:1]
+	}
+	s.entries[0].child = -1
+	s.entries[0].next = -1
 }
 
 type entry struct {
-	id       int
+	// Use -1 to indicate no child or no sibling.
-	parent   int
+	child int
+	next  int
+
 	name     []byte
 	kind     keyKind
 	explicit bool
 }
 
-// Remove all descendent of node at position idx.
+// Find the index of the child of parentIdx with key k. Returns -1 if
-func (s *SeenTracker) clear(idx int) {
+// it does not exist.
-	p := s.entries[idx].id
+func (s *SeenTracker) find(parentIdx int, k []byte) int {
-	rest := clear(p, s.entries[idx+1:])
+	for i := s.entries[parentIdx].child; i >= 0; i = s.entries[i].next {
-	s.entries = s.entries[:idx+1+len(rest)]
+		if bytes.Equal(s.entries[i].name, k) {
-}
+			return i
-
-func clear(parentID int, entries []entry) []entry {
-	for i := 0; i < len(entries); {
-		if entries[i].parent == parentID {
-			id := entries[i].id
-			copy(entries[i:], entries[i+1:])
-			entries = entries[:len(entries)-1]
-			rest := clear(id, entries[i:])
-			entries = entries[:i+len(rest)]
-		} else {
-			i++
 		}
 	}
-	return entries
+	return -1
+}
+
+// Remove all descendants of node at position idx.
+func (s *SeenTracker) clear(idx int) {
+	if idx >= len(s.entries) {
+		return
+	}
+
+	for i := s.entries[idx].child; i >= 0; {
+		next := s.entries[i].next
+		n := s.entries[0].next
+		s.entries[0].next = i
+		s.entries[i].next = n
+		s.entries[i].name = nil
+		s.clear(i)
+		i = next
+	}
+
+	s.entries[idx].child = -1
 }
 
 func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit bool) int {
-	parentID := s.id(parentIdx)
+	e := entry{
+		child: -1,
+		next:  s.entries[parentIdx].child,
 
-	idx := len(s.entries)
-	s.entries = append(s.entries, entry{
-		id:       s.nextID,
-		parent:   parentID,
 		name:     name,
 		kind:     kind,
 		explicit: explicit,
-	})
+	}
-	s.nextID++
+	var idx int
+	if s.entries[0].next >= 0 {
+		idx = s.entries[0].next
+		s.entries[0].next = s.entries[idx].next
+		s.entries[idx] = e
+	} else {
+		idx = len(s.entries)
+		s.entries = append(s.entries, e)
+	}
+
+	s.entries[parentIdx].child = idx
+
 	return idx
 }
 
-// CheckExpression takes a top-level node and checks that it does not contain keys
+func (s *SeenTracker) setExplicitFlag(parentIdx int) {
-// that have been seen in previous calls, and validates that types are consistent.
+	for i := s.entries[parentIdx].child; i >= 0; i = s.entries[i].next {
+		s.entries[i].explicit = true
+		s.setExplicitFlag(i)
+	}
+}
+
+// CheckExpression takes a top-level node and checks that it does not contain
+// keys that have been seen in previous calls, and validates that types are
+// consistent.
 func (s *SeenTracker) CheckExpression(node *ast.Node) error {
 	if s.entries == nil {
-		// Skip ID = 0 to remove the confusion between nodes whose parent has
+		s.reset()
-		// id 0 and root nodes (parent id is 0 because it's the zero value).
-		s.nextID = 1
-		// Start unscoped, so idx is negative.
-		s.currentIdx = -1
 	}
 	switch node.Kind {
 	case ast.KeyValue:
@@ -125,9 +162,13 @@ func (s *SeenTracker) CheckExpression(node *ast.Node) error {
 }
 
 func (s *SeenTracker) checkTable(node *ast.Node) error {
+	if s.currentIdx >= 0 {
+		s.setExplicitFlag(s.currentIdx)
+	}
+
 	it := node.Key()
 
-	parentIdx := -1
+	parentIdx := 0
 
 	// This code is duplicated in checkArrayTable. This is because factoring
 	// it in a function requires to copy the iterator, or allocate it to the
@@ -143,6 +184,11 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 
 		if idx < 0 {
 			idx = s.create(parentIdx, k, tableKind, false)
+		} else {
+			entry := s.entries[idx]
+			if entry.kind == valueKind {
+				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+			}
 		}
 		parentIdx = idx
 	}
@@ -169,9 +215,13 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 }
 
 func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
+	if s.currentIdx >= 0 {
+		s.setExplicitFlag(s.currentIdx)
+	}
+
 	it := node.Key()
 
-	parentIdx := -1
+	parentIdx := 0
 
 	for it.Next() {
 		if it.IsLast() {
@@ -184,7 +234,13 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 
 		if idx < 0 {
 			idx = s.create(parentIdx, k, tableKind, false)
+		} else {
+			entry := s.entries[idx]
+			if entry.kind == valueKind {
+				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+			}
 		}
+
 		parentIdx = idx
 	}
 
@@ -207,53 +263,89 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 }
 
 func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
-	it := node.Key()
-
 	parentIdx := s.currentIdx
+	it := node.Key()
 
 	for it.Next() {
 		k := it.Node().Data
 
 		idx := s.find(parentIdx, k)
 
-		if idx >= 0 {
+		if idx < 0 {
-			if s.entries[idx].kind != tableKind {
+			idx = s.create(parentIdx, k, tableKind, false)
-				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), s.entries[idx].kind)
+		} else {
-			}
+			entry := s.entries[idx]
-			if s.entries[idx].explicit {
+			if it.IsLast() {
+				return fmt.Errorf("toml: key %s is already defined", string(k))
+			} else if entry.kind != tableKind {
+				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+			} else if entry.explicit {
 				return fmt.Errorf("toml: cannot redefine table %s that has already been explicitly defined", string(k))
 			}
-		} else {
-			idx = s.create(parentIdx, k, tableKind, false)
 		}
+
 		parentIdx = idx
 	}
 
-	kind := valueKind
+	s.entries[parentIdx].kind = valueKind
 
-	if node.Value().Kind == ast.InlineTable {
+	value := node.Value()
-		kind = tableKind
+
+	switch value.Kind {
+	case ast.InlineTable:
+		return s.checkInlineTable(value)
+	case ast.Array:
+		return s.checkArray(value)
 	}
-	s.entries[parentIdx].kind = kind
 
 	return nil
 }
 
-func (s *SeenTracker) id(idx int) int {
+func (s *SeenTracker) checkArray(node *ast.Node) error {
-	if idx >= 0 {
+	it := node.Children()
-		return s.entries[idx].id
+	for it.Next() {
+		n := it.Node()
+		switch n.Kind {
+		case ast.InlineTable:
+			err := s.checkInlineTable(n)
+			if err != nil {
+				return err
+			}
+		case ast.Array:
+			err := s.checkArray(n)
+			if err != nil {
+				return err
+			}
+		}
 	}
-	return 0
+	return nil
 }
 
-func (s *SeenTracker) find(parentIdx int, k []byte) int {
+func (s *SeenTracker) checkInlineTable(node *ast.Node) error {
-	parentID := s.id(parentIdx)
+	if pool.New == nil {
-
+		pool.New = func() interface{} {
-	for i := parentIdx + 1; i < len(s.entries); i++ {
+			return &SeenTracker{}
-		if s.entries[i].parent == parentID && bytes.Equal(s.entries[i].name, k) {
-			return i
 		}
 	}
 
-	return -1
+	s = pool.Get().(*SeenTracker)
+	s.reset()
+
+	it := node.Children()
+	for it.Next() {
+		n := it.Node()
+		err := s.checkKeyValue(n)
+		if err != nil {
+			return err
+		}
+	}
+
+	// As inline tables are self-contained, the tracker does not
+	// need to retain the details of what they contain. The
+	// keyValue element that creates the inline table is kept to
+	// mark the presence of the inline table and prevent
+	// redefinition of its keys: check* functions cannot walk into
+	// a value.
+	pool.Put(s)
+	return nil
 }

marshaler.go

@@ -11,6 +11,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"unicode"
 )
 
 // Marshal serializes a Go value as a TOML document.
@@ -54,8 +55,9 @@ func NewEncoder(w io.Writer) *Encoder {
 // inline tag:
 //
 //   MyField `inline:"true"`
-func (enc *Encoder) SetTablesInline(inline bool) {
+func (enc *Encoder) SetTablesInline(inline bool) *Encoder {
 	enc.tablesInline = inline
+	return enc
 }
 
 // SetArraysMultiline forces the encoder to emit all arrays with one element per
@@ -64,20 +66,23 @@ func (enc *Encoder) SetTablesInline(inline bool) {
 // This behavior can be controlled on an individual struct field basis with the multiline tag:
 //
 //   MyField `multiline:"true"`
-func (enc *Encoder) SetArraysMultiline(multiline bool) {
+func (enc *Encoder) SetArraysMultiline(multiline bool) *Encoder {
 	enc.arraysMultiline = multiline
+	return enc
 }
 
 // SetIndentSymbol defines the string that should be used for indentation. The
 // provided string is repeated for each indentation level. Defaults to two
 // spaces.
-func (enc *Encoder) SetIndentSymbol(s string) {
+func (enc *Encoder) SetIndentSymbol(s string) *Encoder {
 	enc.indentSymbol = s
+	return enc
 }
 
 // SetIndentTables forces the encoder to intent tables and array tables.
-func (enc *Encoder) SetIndentTables(indent bool) {
+func (enc *Encoder) SetIndentTables(indent bool) *Encoder {
 	enc.indentTables = indent
+	return enc
 }
 
 // Encode writes a TOML representation of v to the stream.
@@ -99,27 +104,31 @@ func (enc *Encoder) SetIndentTables(indent bool) {
 // Intermediate tables are always printed.
 //
 // By default, strings are encoded as literal string, unless they contain either
-// a newline character or a single quote. In that case they are emitted as quoted
+// a newline character or a single quote. In that case they are emitted as
-// strings.
+// quoted strings.
 //
 // When encoding structs, fields are encoded in order of definition, with their
 // exact name.
 //
 // Struct tags
 //
-// The following struct tags are available to tweak encoding on a per-field
+// The encoding of each public struct field can be customized by the format
-// basis:
+// string in the "toml" key of the struct field's tag. This follows
+// encoding/json's convention. The format string starts with the name of the
+// field, optionally followed by a comma-separated list of options. The name may
+// be empty in order to provide options without overriding the default name.
 //
-//   toml:"foo"
+// The "multiline" option emits strings as quoted multi-line TOML strings. It
-//     Changes the name of the key to use for the field to foo.
+// has no effect on fields that would not be encoded as strings.
 //
-//   multiline:"true"
+// The "inline" option turns fields that would be emitted as tables into inline
-//     When the field contains a string, it will be emitted as a quoted
+// tables instead. It has no effect on other fields.
-//     multi-line TOML string.
 //
-//   inline:"true"
+// The "omitempty" option prevents empty values or groups from being emitted.
-//     When the field would normally be encoded as a table, it is instead
+//
-//     encoded as an inline table.
+// In addition to the "toml" tag struct tag, a "comment" tag can be used to emit
+// a TOML comment before the value being annotated. Comments are ignored inside
+// inline tables.
 func (enc *Encoder) Encode(v interface{}) error {
 	var (
 		b   []byte
@@ -147,6 +156,8 @@ func (enc *Encoder) Encode(v interface{}) error {
 
 type valueOptions struct {
 	multiline bool
+	omitempty bool
+	comment   string
 }
 
 type encoderCtx struct {
@@ -196,7 +207,6 @@ func (ctx *encoderCtx) isRoot() bool {
 	return len(ctx.parentKey) == 0 && !ctx.hasKey
 }
 
-//nolint:cyclop,funlen
 func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
 	if !v.IsZero() {
 		i, ok := v.Interface().(time.Time)
@@ -205,7 +215,12 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 		}
 	}
 
-	if v.Type().Implements(textMarshalerType) {
+	hasTextMarshaler := v.Type().Implements(textMarshalerType)
+	if hasTextMarshaler || (v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
+		if !hasTextMarshaler {
+			v = v.Addr()
+		}
+
 		if ctx.isRoot() {
 			return nil, fmt.Errorf("toml: type %s implementing the TextMarshaler interface cannot be a root element", v.Type())
 		}
@@ -288,6 +303,15 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 	if !ctx.hasKey {
 		panic("caller of encodeKv should have set the key in the context")
 	}
+
+	if (ctx.options.omitempty || options.omitempty) && isEmptyValue(v) {
+		return b, nil
+	}
+
+	if !ctx.inline {
+		b = enc.encodeComment(ctx.indent, options.comment, b)
+	}
+
 	b = enc.indent(ctx.indent, b)
 
 	b, err = enc.encodeKey(b, ctx.key)
@@ -312,6 +336,24 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 	return b, nil
 }
 
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	}
+	return false
+}
+
 const literalQuote = '\''
 
 func (enc *Encoder) encodeString(b []byte, v string, options valueOptions) []byte {
@@ -405,6 +447,8 @@ func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) ([]byte, error)
 		return b, nil
 	}
 
+	b = enc.encodeComment(ctx.indent, ctx.options.comment, b)
+
 	b = enc.indent(ctx.indent, b)
 
 	b = append(b, '[')
@@ -521,8 +565,7 @@ func (t *table) pushTable(k string, v reflect.Value, options valueOptions) {
 func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
 	var t table
 
-	//nolint:godox
+	// TODO: cache this
-	// TODO: cache this?
 	typ := v.Type()
 	for i := 0; i < typ.NumField(); i++ {
 		fieldType := typ.Field(i)
@@ -532,16 +575,20 @@ func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]b
 			continue
 		}
 
-		k, ok := fieldType.Tag.Lookup("toml")
+		k := fieldType.Name
-		if !ok {
+
-			k = fieldType.Name
+		tag := fieldType.Tag.Get("toml")
-		}
 
 		// special field name to skip field
-		if k == "-" {
+		if tag == "-" {
 			continue
 		}
 
+		name, opts := parseTag(tag)
+		if isValidName(name) {
+			k = name
+		}
+
 		f := v.Field(i)
 
 		if isNil(f) {
@@ -549,12 +596,12 @@ func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]b
 		}
 
 		options := valueOptions{
-			multiline: fieldBoolTag(fieldType, "multiline"),
+			multiline: opts.multiline,
+			omitempty: opts.omitempty,
+			comment:   fieldType.Tag.Get("comment"),
 		}
 
-		inline := fieldBoolTag(fieldType, "inline")
+		if opts.inline || !willConvertToTableOrArrayTable(ctx, f) {
-
-		if inline || !willConvertToTableOrArrayTable(ctx, f) {
 			t.pushKV(k, f, options)
 		} else {
 			t.pushTable(k, f, options)
@@ -564,13 +611,70 @@ func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]b
 	return enc.encodeTable(b, ctx, t)
 }
 
-func fieldBoolTag(field reflect.StructField, tag string) bool {
+func (enc *Encoder) encodeComment(indent int, comment string, b []byte) []byte {
-	x, ok := field.Tag.Lookup(tag)
+	if comment != "" {
-
+		b = enc.indent(indent, b)
-	return ok && x == "true"
+		b = append(b, "# "...)
+		b = append(b, comment...)
+		b = append(b, '\n')
+	}
+	return b
+}
+
+func isValidName(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		switch {
+		case strings.ContainsRune("!#$%&()*+-./:;<=>?@[]^_{|}~ ", c):
+			// Backslash and quote chars are reserved, but
+			// otherwise any punctuation chars are allowed
+			// in a tag name.
+		case !unicode.IsLetter(c) && !unicode.IsDigit(c):
+			return false
+		}
+	}
+	return true
+}
+
+type tagOptions struct {
+	multiline bool
+	inline    bool
+	omitempty bool
+}
+
+func parseTag(tag string) (string, tagOptions) {
+	opts := tagOptions{}
+
+	idx := strings.Index(tag, ",")
+	if idx == -1 {
+		return tag, opts
+	}
+
+	raw := tag[idx+1:]
+	tag = string(tag[:idx])
+	for raw != "" {
+		var o string
+		i := strings.Index(raw, ",")
+		if i >= 0 {
+			o, raw = raw[:i], raw[i+1:]
+		} else {
+			o, raw = raw, ""
+		}
+		switch o {
+		case "multiline":
+			opts.multiline = true
+		case "inline":
+			opts.inline = true
+		case "omitempty":
+			opts.omitempty = true
+		}
+	}
+
+	return tag, opts
 }
 
-//nolint:cyclop
 func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, error) {
 	var err error
 
@@ -653,7 +757,7 @@ func willConvertToTable(ctx encoderCtx, v reflect.Value) bool {
 	if !v.IsValid() {
 		return false
 	}
-	if v.Type() == timeType || v.Type().Implements(textMarshalerType) {
+	if v.Type() == timeType || v.Type().Implements(textMarshalerType) || (v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
 		return false
 	}
 

marshaler_test.go

@@ -4,20 +4,27 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"math/big"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/pelletier/go-toml/v2"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-//nolint:funlen
 func TestMarshal(t *testing.T) {
 	someInt := 42
 
 	type structInline struct {
-		A interface{} `inline:"true"`
+		A interface{} `toml:",inline"`
+	}
+
+	type comments struct {
+		One   int
+		Two   int   `comment:"Before kv"`
+		Three []int `comment:"Before array"`
 	}
 
 	examples := []struct {
@@ -193,9 +200,9 @@ name = 'Alice'
 		{
 			desc: "string escapes",
 			v: map[string]interface{}{
-				"a": `'"\`,
+				"a": "'\b\f\r\t\"\\",
 			},
-			expected: `a = "'\"\\"`,
+			expected: `a = "'\b\f\r\t\"\\"`,
 		},
 		{
 			desc: "string utf8 low",
@@ -242,7 +249,7 @@ name = 'Alice'
 		{
 			desc: "multi-line forced",
 			v: struct {
-				A string `multiline:"true"`
+				A string `toml:",multiline"`
 			}{
 				A: "hello\nworld",
 			},
@@ -253,7 +260,7 @@ world"""`,
 		{
 			desc: "inline field",
 			v: struct {
-				A map[string]string `inline:"true"`
+				A map[string]string `toml:",inline"`
 				B map[string]string
 			}{
 				A: map[string]string{
@@ -272,7 +279,7 @@ isinline = 'no'
 		{
 			desc: "mutiline array int",
 			v: struct {
-				A []int `multiline:"true"`
+				A []int `toml:",multiline"`
 				B []int
 			}{
 				A: []int{1, 2, 3, 4},
@@ -291,7 +298,7 @@ B = [1, 2, 3, 4]
 		{
 			desc: "mutiline array in array",
 			v: struct {
-				A [][]int `multiline:"true"`
+				A [][]int `toml:",multiline"`
 			}{
 				A: [][]int{{1, 2}, {3, 4}},
 			},
@@ -469,6 +476,28 @@ hello = 'world'`,
 			},
 			err: true,
 		},
+		{
+			desc: "time",
+			v: struct {
+				T time.Time
+			}{
+				T: time.Time{},
+			},
+			expected: `T = '0001-01-01T00:00:00Z'`,
+		},
+		{
+			desc: "bool",
+			v: struct {
+				A bool
+				B bool
+			}{
+				A: false,
+				B: true,
+			},
+			expected: `
+A = false
+B = true`,
+		},
 		{
 			desc: "numbers",
 			v: struct {
@@ -483,6 +512,7 @@ hello = 'world'`,
 				I int16
 				J int8
 				K int
+				L float64
 			}{
 				A: 1.1,
 				B: 42,
@@ -495,6 +525,7 @@ hello = 'world'`,
 				I: 42,
 				J: 42,
 				K: 42,
+				L: 2.2,
 			},
 			expected: `
 A = 1.1
@@ -507,7 +538,29 @@ G = 42
 H = 42
 I = 42
 J = 42
-K = 42`,
+K = 42
+L = 2.2`,
+		},
+		{
+			desc: "comments",
+			v: struct {
+				Table comments `comment:"Before table"`
+			}{
+				Table: comments{
+					One:   1,
+					Two:   2,
+					Three: []int{1, 2, 3},
+				},
+			},
+			expected: `
+# Before table
+[Table]
+One = 1
+# Before kv
+Two = 2
+# Before array
+Three = [1, 2, 3]
+`,
 		},
 	}
 
@@ -551,7 +604,7 @@ K = 42`,
 
 type flagsSetters []struct {
 	name string
-	f    func(enc *toml.Encoder, flag bool)
+	f    func(enc *toml.Encoder, flag bool) *toml.Encoder
 }
 
 var allFlags = flagsSetters{
@@ -734,6 +787,60 @@ func TestEncoderSetIndentSymbol(t *testing.T) {
 	equalStringsIgnoreNewlines(t, expected, w.String())
 }
 
+func TestEncoderOmitempty(t *testing.T) {
+	type doc struct {
+		String  string            `toml:",omitempty,multiline"`
+		Bool    bool              `toml:",omitempty,multiline"`
+		Int     int               `toml:",omitempty,multiline"`
+		Int8    int8              `toml:",omitempty,multiline"`
+		Int16   int16             `toml:",omitempty,multiline"`
+		Int32   int32             `toml:",omitempty,multiline"`
+		Int64   int64             `toml:",omitempty,multiline"`
+		Uint    uint              `toml:",omitempty,multiline"`
+		Uint8   uint8             `toml:",omitempty,multiline"`
+		Uint16  uint16            `toml:",omitempty,multiline"`
+		Uint32  uint32            `toml:",omitempty,multiline"`
+		Uint64  uint64            `toml:",omitempty,multiline"`
+		Float32 float32           `toml:",omitempty,multiline"`
+		Float64 float64           `toml:",omitempty,multiline"`
+		MapNil  map[string]string `toml:",omitempty,multiline"`
+		Slice   []string          `toml:",omitempty,multiline"`
+		Ptr     *string           `toml:",omitempty,multiline"`
+		Iface   interface{}       `toml:",omitempty,multiline"`
+		Struct  struct{}          `toml:",omitempty,multiline"`
+	}
+
+	d := doc{}
+
+	b, err := toml.Marshal(d)
+	require.NoError(t, err)
+
+	expected := `[Struct]`
+
+	equalStringsIgnoreNewlines(t, expected, string(b))
+}
+
+func TestEncoderTagFieldName(t *testing.T) {
+	type doc struct {
+		String string `toml:"hello"`
+		OkSym  string `toml:"#"`
+		Bad    string `toml:"\"`
+	}
+
+	d := doc{String: "world"}
+
+	b, err := toml.Marshal(d)
+	require.NoError(t, err)
+
+	expected := `
+hello = 'world'
+'#' = ''
+Bad = ''
+`
+
+	equalStringsIgnoreNewlines(t, expected, string(b))
+}
+
 func TestIssue436(t *testing.T) {
 	data := []byte(`{"a": [ { "b": { "c": "d" } } ]}`)
 
@@ -798,6 +905,48 @@ func TestIssue590(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestIssue571(t *testing.T) {
+	type Foo struct {
+		Float32 float32
+		Float64 float64
+	}
+
+	const closeEnough = 1e-9
+
+	foo := Foo{
+		Float32: 42,
+		Float64: 43,
+	}
+	b, err := toml.Marshal(foo)
+	require.NoError(t, err)
+
+	var foo2 Foo
+	err = toml.Unmarshal(b, &foo2)
+	require.NoError(t, err)
+
+	assert.InDelta(t, 42, foo2.Float32, closeEnough)
+	assert.InDelta(t, 43, foo2.Float64, closeEnough)
+}
+
+func TestIssue678(t *testing.T) {
+	type Config struct {
+		BigInt big.Int
+	}
+
+	cfg := &Config{
+		BigInt: *big.NewInt(123),
+	}
+
+	out, err := toml.Marshal(cfg)
+	require.NoError(t, err)
+	equalStringsIgnoreNewlines(t, "BigInt = '123'", string(out))
+
+	cfg2 := &Config{}
+	err = toml.Unmarshal(out, cfg2)
+	require.NoError(t, err)
+	require.Equal(t, cfg, cfg2)
+}
+
 func ExampleMarshal() {
 	type MyConfig struct {
 		Version int
@@ -822,26 +971,3 @@ func ExampleMarshal() {
 	// Name = 'go-toml'
 	// Tags = ['go', 'toml']
 }
-
-func TestIssue571(t *testing.T) {
-	type Foo struct {
-		Float32 float32
-		Float64 float64
-	}
-
-	const closeEnough = 1e-9
-
-	foo := Foo{
-		Float32: 42,
-		Float64: 43,
-	}
-	b, err := toml.Marshal(foo)
-	require.NoError(t, err)
-
-	var foo2 Foo
-	err = toml.Unmarshal(b, &foo2)
-	require.NoError(t, err)
-
-	assert.InDelta(t, 42, foo2.Float32, closeEnough)
-	assert.InDelta(t, 43, foo2.Float64, closeEnough)
-}

parser.go

@@ -549,7 +549,7 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 	startIdx := i
 	endIdx := len(token) - len(`"""`)
 
-	if escaped < 0 {
+	if !escaped {
 		str := token[startIdx:endIdx]
 		verr := utf8TomlValidAlreadyEscaped(str)
 		if verr.Zero() {
@@ -578,6 +578,10 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 				switch token[i+j] {
 				case ' ', '\t':
 					continue
+				case '\r':
+					if token[i+j+1] == '\n' {
+						continue
+					}
 				case '\n':
 					isLastNonWhitespaceOnLine = true
 				}
@@ -689,13 +693,13 @@ func (p *parser) parseKey(b []byte) (ast.Reference, []byte, error) {
 }
 
 func (p *parser) parseSimpleKey(b []byte) (raw, key, rest []byte, err error) {
+	if len(b) == 0 {
+		return nil, nil, nil, newDecodeError(b, "expected key but found none")
+	}
+
 	// simple-key = quoted-key / unquoted-key
 	// unquoted-key = 1*( ALPHA / DIGIT / %x2D / %x5F ) ; A-Z / a-z / 0-9 / - / _
 	// quoted-key = basic-string / literal-string
-	if len(b) == 0 {
-		return nil, nil, nil, newDecodeError(b, "key is incomplete")
-	}
-
 	switch {
 	case b[0] == '\'':
 		return p.parseLiteralString(b)
@@ -736,7 +740,7 @@ func (p *parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
 	// Fast path. If there is no escape sequence, the string should just be
 	// an UTF-8 encoded string, which is the same as Go. In that case,
 	// validate the string and return a direct reference to the buffer.
-	if escaped < 0 {
+	if !escaped {
 		str := token[startIdx:endIdx]
 		verr := utf8TomlValidAlreadyEscaped(str)
 		if verr.Zero() {
@@ -866,7 +870,6 @@ func (p *parser) parseIntOrFloatOrDateTime(b []byte) (ast.Reference, []byte, err
 		return p.scanIntOrFloat(b)
 	}
 
-	//nolint:gomnd
 	if len(b) < 3 {
 		return p.scanIntOrFloat(b)
 	}
@@ -884,23 +887,13 @@ func (p *parser) parseIntOrFloatOrDateTime(b []byte) (ast.Reference, []byte, err
 		if idx == 2 && c == ':' || (idx == 4 && c == '-') {
 			return p.scanDateTime(b)
 		}
+
+		break
 	}
 
 	return p.scanIntOrFloat(b)
 }
 
-func digitsToInt(b []byte) int {
-	x := 0
-
-	for _, d := range b {
-		x *= 10
-		x += int(d - '0')
-	}
-
-	return x
-}
-
-//nolint:gocognit,cyclop
 func (p *parser) scanDateTime(b []byte) (ast.Reference, []byte, error) {
 	// scans for contiguous characters in [0-9T:Z.+-], and up to one space if
 	// followed by a digit.
@@ -970,7 +963,7 @@ byteLoop:
 func (p *parser) scanIntOrFloat(b []byte) (ast.Reference, []byte, error) {
 	i := 0
 
-	if len(b) > 2 && b[0] == '0' && b[1] != '.' && b[1] != 'e' {
+	if len(b) > 2 && b[0] == '0' && b[1] != '.' && b[1] != 'e' && b[1] != 'E' {
 		var isValidRune validRuneFn
 
 		switch b[1] {

parser_test.go

@@ -1,6 +1,8 @@
 package toml
 
 import (
+	"strconv"
+	"strings"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2/internal/ast"
@@ -371,6 +373,23 @@ func BenchmarkParseBasicStringWithUnicode(b *testing.B) {
 	})
 }
 
+func BenchmarkParseBasicStringsEasy(b *testing.B) {
+	p := &parser{}
+
+	for _, size := range []int{1, 4, 8, 16, 21} {
+		b.Run(strconv.Itoa(size), func(b *testing.B) {
+			input := []byte(`"` + strings.Repeat("A", size) + `"`)
+
+			b.ReportAllocs()
+			b.SetBytes(int64(len(input)))
+
+			for i := 0; i < b.N; i++ {
+				p.parseBasicString(input)
+			}
+		})
+	}
+}
+
 func TestParser_AST_DateTimes(t *testing.T) {
 	examples := []struct {
 		desc  string

scanner.go

@@ -53,7 +53,7 @@ func scanLiteralString(b []byte) ([]byte, []byte, error) {
 		switch b[i] {
 		case '\'':
 			return b[:i+1], b[i+1:], nil
-		case '\n':
+		case '\n', '\r':
 			return nil, nil, newDecodeError(b[i:i+1], "literal strings cannot have new lines")
 		}
 		size := utf8ValidNext(b[i:])
@@ -76,30 +76,42 @@ func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
 	// mll-char = %x09 / %x20-26 / %x28-7E / non-ascii
 	// mll-quotes = 1*2apostrophe
 	for i := 3; i < len(b); {
-		if scanFollowsMultilineLiteralStringDelimiter(b[i:]) {
+		switch b[i] {
-			i += 3
+		case '\'':
+			if scanFollowsMultilineLiteralStringDelimiter(b[i:]) {
+				i += 3
 
-			// At that point we found 3 apostrophe, and i is the
+				// At that point we found 3 apostrophe, and i is the
-			// index of the byte after the third one. The scanner
+				// index of the byte after the third one. The scanner
-			// needs to be eager, because there can be an extra 2
+				// needs to be eager, because there can be an extra 2
-			// apostrophe that can be accepted at the end of the
+				// apostrophe that can be accepted at the end of the
-			// string.
+				// string.
+
+				if i >= len(b) || b[i] != '\'' {
+					return b[:i], b[i:], nil
+				}
+				i++
+
+				if i >= len(b) || b[i] != '\'' {
+					return b[:i], b[i:], nil
+				}
+				i++
+
+				if i < len(b) && b[i] == '\'' {
+					return nil, nil, newDecodeError(b[i-3:i+1], "''' not allowed in multiline literal string")
+				}
 
-			if i >= len(b) || b[i] != '\'' {
 				return b[:i], b[i:], nil
 			}
-			i++
+		case '\r':
-
+			if len(b) < i+2 {
-			if i >= len(b) || b[i] != '\'' {
+				return nil, nil, newDecodeError(b[len(b):], `need a \n after \r`)
-				return b[:i], b[i:], nil
 			}
-			i++
+			if b[i+1] != '\n' {
-
+				return nil, nil, newDecodeError(b[i:i+2], `need a \n after \r`)
-			if i < len(b) && b[i] == '\'' {
-				return nil, nil, newDecodeError(b[i-3:i+1], "''' not allowed in multiline literal string")
 			}
-
+			i += 2 // skip the \n
-			return b[:i], b[i:], nil
+			continue
 		}
 		size := utf8ValidNext(b[i:])
 		if size == 0 {
@@ -149,6 +161,12 @@ func scanComment(b []byte) ([]byte, []byte, error) {
 		if b[i] == '\n' {
 			return b[:i], b[i:], nil
 		}
+		if b[i] == '\r' {
+			if i+1 < len(b) && b[i+1] == '\n' {
+				return b[:i+1], b[i+1:], nil
+			}
+			return nil, nil, newDecodeError(b[i:i+1], "invalid character in comment")
+		}
 		size := utf8ValidNext(b[i:])
 		if size == 0 {
 			return nil, nil, newDecodeError(b[i:i+1], "invalid character in comment")
@@ -160,42 +178,26 @@ func scanComment(b []byte) ([]byte, []byte, error) {
 	return b, b[len(b):], nil
 }
 
-func scanBasicString(b []byte) ([]byte, int, []byte, error) {
+func scanBasicString(b []byte) ([]byte, bool, []byte, error) {
 	// basic-string = quotation-mark *basic-char quotation-mark
 	// quotation-mark = %x22            ; "
 	// basic-char = basic-unescaped / escaped
 	// basic-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
 	// escaped = escape escape-seq-char
-	escaped := -1 // index of the first \. -1 means no escape character in there.
+	escaped := false
 	i := 1
 
-loop:
 	for ; i < len(b); i++ {
 		switch b[i] {
 		case '"':
 			return b[:i+1], escaped, b[i+1:], nil
-		case '\n':
+		case '\n', '\r':
-			return nil, escaped, nil, newDecodeError(b[i:i+1], "basic strings cannot have new lines")
-		case '\\':
-			if len(b) < i+2 {
-				return nil, escaped, nil, newDecodeError(b[i:i+1], "need a character after \\")
-			}
-			escaped = i
-			i += 2 // skip the next character
-			break loop
-		}
-	}
-
-	for ; i < len(b); i++ {
-		switch b[i] {
-		case '"':
-			return b[:i+1], escaped, b[i+1:], nil
-		case '\n':
 			return nil, escaped, nil, newDecodeError(b[i:i+1], "basic strings cannot have new lines")
 		case '\\':
 			if len(b) < i+2 {
 				return nil, escaped, nil, newDecodeError(b[i:i+1], "need a character after \\")
 			}
+			escaped = true
 			i++ // skip the next character
 		}
 	}
@@ -203,7 +205,7 @@ loop:
 	return nil, escaped, nil, newDecodeError(b[len(b):], `basic string not terminated by "`)
 }
 
-func scanMultilineBasicString(b []byte) ([]byte, int, []byte, error) {
+func scanMultilineBasicString(b []byte) ([]byte, bool, []byte, error) {
 	// ml-basic-string = ml-basic-string-delim [ newline ] ml-basic-body
 	// ml-basic-string-delim
 	// ml-basic-string-delim = 3quotation-mark
@@ -215,10 +217,9 @@ func scanMultilineBasicString(b []byte) ([]byte, int, []byte, error) {
 	// mlb-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
 	// mlb-escaped-nl = escape ws newline *( wschar / newline )
 
-	escaped := -1
+	escaped := false
 	i := 3
 
-loop:
 	for ; i < len(b); i++ {
 		switch b[i] {
 		case '"':
@@ -251,23 +252,16 @@ loop:
 			if len(b) < i+2 {
 				return nil, escaped, nil, newDecodeError(b[len(b):], "need a character after \\")
 			}
-			escaped = i
+			escaped = true
-			i += 2 // skip the next character
-			break loop
-		}
-	}
-
-	for ; i < len(b); i++ {
-		switch b[i] {
-		case '"':
-			if scanFollowsMultilineBasicStringDelimiter(b[i:]) {
-				return b[:i+3], escaped, b[i+3:], nil
-			}
-		case '\\':
-			if len(b) < i+2 {
-				return nil, escaped, nil, newDecodeError(b[len(b):], "need a character after \\")
-			}
 			i++ // skip the next character
+		case '\r':
+			if len(b) < i+2 {
+				return nil, escaped, nil, newDecodeError(b[len(b):], `need a \n after \r`)
+			}
+			if b[i+1] != '\n' {
+				return nil, escaped, nil, newDecodeError(b[i:i+2], `need a \n after \r`)
+			}
+			i++ // skip the \n
 		}
 	}
 

testsuite/testsuite.go

@@ -43,7 +43,7 @@ func DecodeStdin() error {
 	j := json.NewEncoder(os.Stdout)
 	j.SetIndent("", "  ")
 	if err := j.Encode(addTag("", decoded)); err != nil {
-		fmt.Errorf("Error encoding JSON: %s", err)
+		return fmt.Errorf("Error encoding JSON: %s", err)
 	}
 
 	return nil

toml_testgen_test.go

@@ -1,4 +1,4 @@
-// Generated by tomltestgen for toml-test ref master on 2021-09-30T20:29:36-05:00
+// Generated by tomltestgen for toml-test ref master on 2021-11-08T22:33:24-05:00
 package toml_test
 
 import (
@@ -375,6 +375,11 @@ func TestTOMLTest_Invalid_Float_TrailingPoint(t *testing.T) {
 	testgenInvalid(t, input)
 }
 
+func TestTOMLTest_Invalid_Float_TrailingUsExp(t *testing.T) {
+	input := "# trailing underscore in integer part is not allowed\ntrailing-us-exp = 1_e2\n# trailing underscore in float part is not allowed\ntrailing-us-exp2 = 1.2_e2\n"
+	testgenInvalid(t, input)
+}
+
 func TestTOMLTest_Invalid_Float_TrailingUs(t *testing.T) {
 	input := "trailing-us = 1.2_\n"
 	testgenInvalid(t, input)
@@ -395,6 +400,11 @@ func TestTOMLTest_Invalid_InlineTable_DoubleComma(t *testing.T) {
 	testgenInvalid(t, input)
 }
 
+func TestTOMLTest_Invalid_InlineTable_DuplicateKey(t *testing.T) {
+	input := "# Duplicate keys within an inline table are invalid\na={b=1, b=2}\n"
+	testgenInvalid(t, input)
+}
+
 func TestTOMLTest_Invalid_InlineTable_Empty(t *testing.T) {
 	input := "t = {,}\n"
 	testgenInvalid(t, input)

types.go

@@ -11,3 +11,4 @@ var textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
 var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
 var mapStringInterfaceType = reflect.TypeOf(map[string]interface{}{})
 var sliceInterfaceType = reflect.TypeOf([]interface{}{})
+var stringType = reflect.TypeOf("")

unmarshaler.go

@@ -9,10 +9,11 @@ import (
 	"math"
 	"reflect"
 	"strings"
-	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/pelletier/go-toml/v2/internal/ast"
+	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/internal/tracker"
 )
 
@@ -47,8 +48,9 @@ func NewDecoder(r io.Reader) *Decoder {
 // that could not be set on the target value. In that case, the decoder returns
 // a StrictMissingError that can be used to retrieve the individual errors as
 // well as generate a human readable description of the missing fields.
-func (d *Decoder) SetStrict(strict bool) {
+func (d *Decoder) SetStrict(strict bool) *Decoder {
 	d.strict = strict
+	return d
 }
 
 // Decode the whole content of r into v.
@@ -58,7 +60,8 @@ func (d *Decoder) SetStrict(strict bool) {
 //
 // When a TOML local date, time, or date-time is decoded into a time.Time, its
 // value is represented in time.Local timezone. Otherwise the approriate Local*
-// structure is used.
+// structure is used. For time values, precision up to the nanosecond is
+// supported by truncating extra digits.
 //
 // Empty tables decoded in an interface{} create an empty initialized
 // map[string]interface{}.
@@ -70,6 +73,11 @@ func (d *Decoder) SetStrict(strict bool) {
 // bounds for the target type (which includes negative numbers when decoding
 // into an unsigned int).
 //
+// If an error occurs while decoding the content of the document, this function
+// returns a toml.DecodeError, providing context about the issue. When using
+// strict mode and a field is missing, a `toml.StrictMissingError` is
+// returned. In any other case, this function returns a standard Go error.
+//
 // Type mapping
 //
 // List of supported TOML types and their associated accepted Go types:
@@ -129,6 +137,23 @@ type decoder struct {
 
 	// Strict mode
 	strict strict
+
+	// Current context for the error.
+	errorContext *errorContext
+}
+
+type errorContext struct {
+	Struct reflect.Type
+	Field  []int
+}
+
+func (d *decoder) typeMismatchError(toml string, target reflect.Type) error {
+	if d.errorContext != nil && d.errorContext.Struct != nil {
+		ctx := d.errorContext
+		f := ctx.Struct.FieldByIndex(ctx.Field)
+		return fmt.Errorf("toml: cannot decode TOML %s into struct field %s.%s of type %s", toml, ctx.Struct, f.Name, f.Type)
+	}
+	return fmt.Errorf("toml: cannot decode TOML %s into a Go value of type %s", toml, target)
 }
 
 func (d *decoder) expr() *ast.Node {
@@ -343,7 +368,9 @@ func (d *decoder) handleArrayTableCollection(key ast.Iterator, v reflect.Value)
 		if err != nil {
 			return reflect.Value{}, err
 		}
-		v.Elem().Set(elem)
+		if elem.IsValid() {
+			v.Elem().Set(elem)
+		}
 
 		return v, nil
 	case reflect.Slice:
@@ -384,12 +411,14 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 		elem = v.Elem()
 		return d.handleKeyPart(key, elem, nextFn, makeFn)
 	case reflect.Map:
+
 		// Create the key for the map element. For now assume it's a string.
 		mk := reflect.ValueOf(string(key.Node().Data))
 
 		// If the map does not exist, create it.
 		if v.IsNil() {
-			v = reflect.MakeMap(v.Type())
+			vt := v.Type()
+			v = reflect.MakeMap(vt)
 			rv = v
 		}
 
@@ -401,7 +430,8 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 			// map[string]interface{} or a []interface{} depending on whether
 			// this is the last part of the array table key.
 
-			t := v.Type().Elem()
+			vt := v.Type()
+			t := vt.Elem()
 			if t.Kind() == reflect.Interface {
 				mv = makeFn()
 			} else {
@@ -415,7 +445,8 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 			}
 			set = true
 		} else if !mv.CanAddr() {
-			t := v.Type().Elem()
+			vt := v.Type()
+			t := vt.Elem()
 			oldmv := mv
 			mv = reflect.New(t).Elem()
 			mv.Set(oldmv)
@@ -436,12 +467,20 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 			v.SetMapIndex(mk, mv)
 		}
 	case reflect.Struct:
-		f, found := structField(v, string(key.Node().Data))
+		path, found := structFieldPath(v, string(key.Node().Data))
 		if !found {
 			d.skipUntilTable = true
 			return reflect.Value{}, nil
 		}
 
+		if d.errorContext == nil {
+			d.errorContext = new(errorContext)
+		}
+		t := v.Type()
+		d.errorContext.Struct = t
+		d.errorContext.Field = path
+
+		f := v.FieldByIndex(path)
 		x, err := nextFn(key, f)
 		if err != nil || d.skipUntilTable {
 			return reflect.Value{}, err
@@ -449,11 +488,13 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 		if x.IsValid() {
 			f.Set(x)
 		}
+		d.errorContext.Field = nil
+		d.errorContext.Struct = nil
 	case reflect.Interface:
 		if v.Elem().IsValid() {
 			v = v.Elem()
 		} else {
-			v = reflect.MakeMap(mapStringInterfaceType)
+			v = makeMapStringInterface()
 		}
 
 		x, err := d.handleKeyPart(key, v, nextFn, makeFn)
@@ -649,7 +690,7 @@ func (d *decoder) unmarshalArray(array *ast.Node, v reflect.Value) error {
 	default:
 		// TODO: use newDecodeError, but first the parser needs to fill
 		//   array.Data.
-		return fmt.Errorf("toml: cannot store array in Go type %s", v.Kind())
+		return d.typeMismatchError("array", v.Type())
 	}
 
 	elemType := v.Type().Elem()
@@ -697,7 +738,7 @@ func (d *decoder) unmarshalInlineTable(itable *ast.Node, v reflect.Value) error
 	case reflect.Interface:
 		elem := v.Elem()
 		if !elem.IsValid() {
-			elem = reflect.MakeMap(mapStringInterfaceType)
+			elem = makeMapStringInterface()
 			v.Set(elem)
 		}
 		return d.unmarshalInlineTable(itable, elem)
@@ -896,7 +937,7 @@ func (d *decoder) unmarshalInteger(value *ast.Node, v reflect.Value) error {
 	case reflect.Interface:
 		r = reflect.ValueOf(i)
 	default:
-		return fmt.Errorf("toml: cannot store TOML integer into a Go %s", v.Kind())
+		return d.typeMismatchError("integer", v.Type())
 	}
 
 	if !r.Type().AssignableTo(v.Type()) {
@@ -953,12 +994,15 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 	// There is no guarantee over what it could be.
 	switch v.Kind() {
 	case reflect.Map:
-		mk := reflect.ValueOf(string(key.Node().Data))
+		vt := v.Type()
 
-		keyType := v.Type().Key()
+		mk := reflect.ValueOf(string(key.Node().Data))
-		if !mk.Type().AssignableTo(keyType) {
+		mkt := stringType
-			if !mk.Type().ConvertibleTo(keyType) {
+
-				return reflect.Value{}, fmt.Errorf("toml: cannot convert map key of type %s to expected type %s", mk.Type(), keyType)
+		keyType := vt.Key()
+		if !mkt.AssignableTo(keyType) {
+			if !mkt.ConvertibleTo(keyType) {
+				return reflect.Value{}, fmt.Errorf("toml: cannot convert map key of type %s to expected type %s", mkt, keyType)
 			}
 
 			mk = mk.Convert(keyType)
@@ -966,7 +1010,7 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 
 		// If the map does not exist, create it.
 		if v.IsNil() {
-			v = reflect.MakeMap(v.Type())
+			v = reflect.MakeMap(vt)
 			rv = v
 		}
 
@@ -996,12 +1040,20 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 			v.SetMapIndex(mk, mv)
 		}
 	case reflect.Struct:
-		f, found := structField(v, string(key.Node().Data))
+		path, found := structFieldPath(v, string(key.Node().Data))
 		if !found {
 			d.skipUntilTable = true
 			break
 		}
 
+		if d.errorContext == nil {
+			d.errorContext = new(errorContext)
+		}
+		t := v.Type()
+		d.errorContext.Struct = t
+		d.errorContext.Field = path
+
+		f := v.FieldByIndex(path)
 		x, err := d.handleKeyValueInner(key, value, f)
 		if err != nil {
 			return reflect.Value{}, err
@@ -1010,14 +1062,17 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 		if x.IsValid() {
 			f.Set(x)
 		}
+		d.errorContext.Struct = nil
+		d.errorContext.Field = nil
 	case reflect.Interface:
 		v = v.Elem()
 
-		// Following encoding/toml: decoding an object into an interface{}, it
+		// Following encoding/json: decoding an object into an
-		// needs to always hold a map[string]interface{}. This is for the types
+		// interface{}, it needs to always hold a
-		// to be consistent whether a previous value was set or not.
+		// map[string]interface{}. This is for the types to be
+		// consistent whether a previous value was set or not.
 		if !v.IsValid() || v.Type() != mapStringInterfaceType {
-			v = reflect.MakeMap(mapStringInterfaceType)
+			v = makeMapStringInterface()
 		}
 
 		x, err := d.handleKeyValuePart(key, value, v)
@@ -1064,80 +1119,68 @@ func initAndDereferencePointer(v reflect.Value) reflect.Value {
 
 type fieldPathsMap = map[string][]int
 
-type fieldPathsCache struct {
+var globalFieldPathsCache atomic.Value // map[danger.TypeID]fieldPathsMap
-	m map[reflect.Type]fieldPathsMap
-	l sync.RWMutex
-}
 
-func (c *fieldPathsCache) get(t reflect.Type) (fieldPathsMap, bool) {
+func structFieldPath(v reflect.Value, name string) ([]int, bool) {
-	c.l.RLock()
+	t := v.Type()
-	paths, ok := c.m[t]
-	c.l.RUnlock()
 
-	return paths, ok
+	cache, _ := globalFieldPathsCache.Load().(map[danger.TypeID]fieldPathsMap)
-}
+	fieldPaths, ok := cache[danger.MakeTypeID(t)]
 
-func (c *fieldPathsCache) set(t reflect.Type, m fieldPathsMap) {
-	c.l.Lock()
-	c.m[t] = m
-	c.l.Unlock()
-}
-
-var globalFieldPathsCache = fieldPathsCache{
-	m: map[reflect.Type]fieldPathsMap{},
-	l: sync.RWMutex{},
-}
-
-func structField(v reflect.Value, name string) (reflect.Value, bool) {
-	//nolint:godox
-	// TODO: cache this, and reduce allocations
-	fieldPaths, ok := globalFieldPathsCache.get(v.Type())
 	if !ok {
 		fieldPaths = map[string][]int{}
 
-		path := make([]int, 0, 16)
+		forEachField(t, nil, func(name string, path []int) {
+			fieldPaths[name] = path
+			// extra copy for the case-insensitive match
+			fieldPaths[strings.ToLower(name)] = path
+		})
 
-		var walk func(reflect.Value)
+		newCache := make(map[danger.TypeID]fieldPathsMap, len(cache)+1)
-		walk = func(v reflect.Value) {
+		newCache[danger.MakeTypeID(t)] = fieldPaths
-			t := v.Type()
+		for k, v := range cache {
-			for i := 0; i < t.NumField(); i++ {
+			newCache[k] = v
-				l := len(path)
-				path = append(path, i)
-				f := t.Field(i)
-
-				if f.Anonymous {
-					walk(v.Field(i))
-				} else if f.PkgPath == "" {
-					// only consider exported fields
-					fieldName, ok := f.Tag.Lookup("toml")
-					if !ok {
-						fieldName = f.Name
-					}
-
-					pathCopy := make([]int, len(path))
-					copy(pathCopy, path)
-
-					fieldPaths[fieldName] = pathCopy
-					// extra copy for the case-insensitive match
-					fieldPaths[strings.ToLower(fieldName)] = pathCopy
-				}
-				path = path[:l]
-			}
 		}
-
+		globalFieldPathsCache.Store(newCache)
-		walk(v)
-
-		globalFieldPathsCache.set(v.Type(), fieldPaths)
 	}
 
 	path, ok := fieldPaths[name]
 	if !ok {
 		path, ok = fieldPaths[strings.ToLower(name)]
 	}
-
+	return path, ok
-	if !ok {
+}
-		return reflect.Value{}, false
+
-	}
+func forEachField(t reflect.Type, path []int, do func(name string, path []int)) {
-
+	n := t.NumField()
-	return v.FieldByIndex(path), true
+	for i := 0; i < n; i++ {
+		f := t.Field(i)
+
+		if !f.Anonymous && f.PkgPath != "" {
+			// only consider exported fields.
+			continue
+		}
+
+		fieldPath := append(path, i)
+		fieldPath = fieldPath[:len(fieldPath):len(fieldPath)]
+
+		if f.Anonymous {
+			forEachField(f.Type, fieldPath, do)
+			continue
+		}
+
+		name := f.Tag.Get("toml")
+		if name == "-" {
+			continue
+		}
+
+		if i := strings.IndexByte(name, ','); i >= 0 {
+			name = name[:i]
+		}
+		if name == "" {
+			name = f.Name
+		}
+
+		do(name, fieldPath)
+	}
 }

utf8.go

@@ -140,8 +140,45 @@ func utf8ValidNext(p []byte) int {
 	return size
 }
 
+var invalidAsciiTable = [256]bool{
+	0x00: true,
+	0x01: true,
+	0x02: true,
+	0x03: true,
+	0x04: true,
+	0x05: true,
+	0x06: true,
+	0x07: true,
+	0x08: true,
+	// 0x09 TAB
+	// 0x0A LF
+	0x0B: true,
+	0x0C: true,
+	// 0x0D CR
+	0x0E: true,
+	0x0F: true,
+	0x10: true,
+	0x11: true,
+	0x12: true,
+	0x13: true,
+	0x14: true,
+	0x15: true,
+	0x16: true,
+	0x17: true,
+	0x18: true,
+	0x19: true,
+	0x1A: true,
+	0x1B: true,
+	0x1C: true,
+	0x1D: true,
+	0x1E: true,
+	0x1F: true,
+	// 0x20 - 0x7E Printable ASCII characters
+	0x7F: true,
+}
+
 func invalidAscii(b byte) bool {
-	return b <= 0x08 || (b > 0x0A && b < 0x0D) || (b > 0x0D && b <= 0x1F) || b == 0x7F
+	return invalidAsciiTable[b]
 }
 
 // acceptRange gives the range of valid values for the second byte in a UTF-8