Nested arrays

internal/reflectbuild/reflectbuild.go

@@ -0,0 +1,239 @@
+// reflectbuild is a package that provides utility functions to build Go
+// objects using reflection.
+package reflectbuild
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// Builder wraps a value and provides method to modify its structure.
+// It is a stateful object that keeps a cursor of what part of the object is
+// being modified.
+// Create a Builder with NewBuilder.
+type Builder struct {
+	root reflect.Value
+	// Root is always a pointer to a non-nil value.
+	// Cursor is the top of the stack.
+	stack []reflect.Value
+}
+
+// NewBuilder creates a Builder to construct v.
+// If v is nil or not a pointer, an error will be returned.
+func NewBuilder(v interface{}) (Builder, error) {
+	if v == nil {
+		return Builder{}, fmt.Errorf("cannot build a nil value")
+	}
+
+	rv := reflect.ValueOf(v)
+	if rv.Type().Kind() != reflect.Ptr {
+		return Builder{}, fmt.Errorf("cannot build a %s: need a pointer", rv.Type().Kind())
+	}
+
+	return Builder{
+		root:  rv.Elem(),
+		stack: []reflect.Value{rv.Elem()},
+	}, nil
+}
+
+func (b *Builder) top() reflect.Value {
+	return b.stack[len(b.stack)-1]
+}
+
+func (b *Builder) push(v reflect.Value) {
+	b.stack = append(b.stack, v)
+}
+
+func (b *Builder) pop() {
+	b.stack = b.stack[:len(b.stack)-1]
+}
+
+func (b *Builder) len() int {
+	return len(b.stack)
+}
+
+func (b *Builder) Dump() string {
+	str := strings.Builder{}
+	str.WriteByte('[')
+
+	for i, x := range b.stack {
+		if i > 0 {
+			str.WriteString(" | ")
+		}
+		fmt.Fprintf(&str, "%s (%s)", x.Type(), x)
+	}
+
+	str.WriteByte(']')
+	return str.String()
+}
+
+func (b *Builder) replace(v reflect.Value) {
+	b.stack[len(b.stack)-1] = v
+}
+
+// DigField pushes the cursor into a field of the current struct.
+// Errors if the current value is not a struct, or the field does not exist.
+func (b *Builder) DigField(s string) error {
+	t := b.top()
+
+	err := checkKind(t.Type(), reflect.Struct)
+	if err != nil {
+		return err
+	}
+
+	f := t.FieldByName(s)
+	if !f.IsValid() {
+		return FieldNotFoundError{FieldName: s, Struct: t}
+	}
+
+	b.replace(f)
+
+	return nil
+}
+
+// Save stores a copy of the current cursor position.
+// It can be restored using Back().
+// Save points are stored as a stack.
+func (b *Builder) Save() {
+	b.push(b.top())
+}
+
+// Reset brings the cursor back to the root object.
+func (b *Builder) Reset() {
+	b.stack = b.stack[:1]
+	b.stack[0] = b.root
+}
+
+// Load is the opposite of Save. It discards the current cursor and loads the
+// last saved cursor.
+// Panics if no cursor has been saved.
+func (b *Builder) Load() {
+	if b.len() < 2 {
+		panic(fmt.Errorf("tried to Back() when cursor was already at root"))
+	}
+	b.pop()
+}
+
+// Cursor returns the value pointed at by the cursor.
+func (b *Builder) Cursor() reflect.Value {
+	return b.top()
+}
+
+func (b *Builder) IsSlice() bool {
+	return b.top().Kind() == reflect.Slice
+}
+
+// Last moves the cursor to the last value of the current value.
+// For a slice or an array, it is the last element they contain, if any.
+// For anything else, it's a no-op.
+func (b *Builder) Last() {
+	switch b.Cursor().Kind() {
+	case reflect.Slice, reflect.Array:
+		length := b.Cursor().Len()
+		if length > 0 {
+			x := b.Cursor().Index(length - 1)
+			b.replace(x)
+		}
+	}
+}
+
+// SliceLastOrCreate moves the cursor to the last element of the slice if any.
+// Otherwise creates a new element in that slice and moves to it.
+func (b *Builder) SliceLastOrCreate() error {
+	t := b.top()
+	err := checkKind(t.Type(), reflect.Slice)
+	if err != nil {
+		return err
+	}
+
+	if t.Len() == 0 {
+		return b.SliceNewElem()
+	}
+	b.Last()
+	return nil
+}
+
+// SliceNewElem operates on a slice. It creates a new object (of type contained
+// by the slice), append it to the slice, and moves the cursor to the new
+// object.
+func (b *Builder) SliceNewElem() error {
+	t := b.top()
+	err := checkKind(t.Type(), reflect.Slice)
+	if err != nil {
+		return err
+	}
+	elem := reflect.New(t.Type().Elem())
+	newSlice := reflect.Append(t, elem.Elem())
+	t.Set(newSlice)
+	b.replace(t.Index(t.Len() - 1))
+	return nil
+}
+
+func (b *Builder) SliceAppend(v reflect.Value) error {
+	t := b.top()
+	err := checkKind(t.Type(), reflect.Slice)
+	if err != nil {
+		return err
+	}
+	newSlice := reflect.Append(t, v)
+	t.Set(newSlice)
+	b.replace(t.Index(t.Len() - 1))
+	return nil
+}
+
+// Set the value at the cursor to the given string.
+// Errors if a string cannot be assigned to the current value.
+func (b *Builder) SetString(s string) error {
+	t := b.top()
+
+	err := checkKind(t.Type(), reflect.String)
+	if err != nil {
+		return err
+	}
+
+	t.SetString(s)
+	return nil
+}
+
+// Set the value at the cursor to the given boolean.
+// Errors if a boolean cannot be assigned to the current value.
+func (b *Builder) SetBool(v bool) error {
+	t := b.top()
+
+	err := checkKind(t.Type(), reflect.Bool)
+	if err != nil {
+		return err
+	}
+
+	t.SetBool(v)
+	return nil
+}
+
+func checkKind(rt reflect.Type, expected reflect.Kind) error {
+	if rt.Kind() != expected {
+		return IncorrectKindError{
+			Actual:   rt.Kind(),
+			Expected: expected,
+		}
+	}
+	return nil
+}
+
+type IncorrectKindError struct {
+	Actual   reflect.Kind
+	Expected reflect.Kind
+}
+
+func (e IncorrectKindError) Error() string {
+	return fmt.Sprintf("incorrect kind: expected '%s', got '%s'", e.Expected, e.Actual)
+}
+
+type FieldNotFoundError struct {
+	Struct    reflect.Value
+	FieldName string
+}
+
+func (e FieldNotFoundError) Error() string {
+	return fmt.Sprintf("field not found: '%s' on '%s'", e.FieldName, e.Struct.Type())
+}

internal/reflectbuild/reflectbuild_test.go

@@ -0,0 +1,167 @@
+package reflectbuild_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/pelletier/go-toml/v2/internal/reflectbuild"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewBuilderSuccess(t *testing.T) {
+	x := struct{}{}
+	_, err := reflectbuild.NewBuilder(&x)
+	assert.NoError(t, err)
+}
+
+func TestNewBuilderNil(t *testing.T) {
+	_, err := reflectbuild.NewBuilder(nil)
+	assert.Error(t, err)
+}
+
+func TestNewBuilderNonPtr(t *testing.T) {
+	_, err := reflectbuild.NewBuilder(struct{}{})
+	assert.Error(t, err)
+}
+
+func TestDigField(t *testing.T) {
+	x := struct {
+		Field string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	assert.Error(t, b.DigField("oops"))
+	assert.NoError(t, b.DigField("Field"))
+	assert.Error(t, b.DigField("does not work on strings"))
+}
+
+func TestBack(t *testing.T) {
+	x := struct {
+		A string
+		B string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	b.Save()
+	assert.NoError(t, b.DigField("A"))
+	assert.NoError(t, b.SetString("A"))
+	b.Load()
+	b.Save()
+	assert.NoError(t, b.DigField("B"))
+	assert.NoError(t, b.SetString("B"))
+	assert.Equal(t, "A", x.A)
+	assert.Equal(t, "B", x.B)
+	b.Load() // back to root
+	assert.Panics(t, func() {
+		b.Load() // oops
+	})
+}
+
+func TestReset(t *testing.T) {
+	x := struct {
+		A []string
+		B string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	require.NoError(t, b.DigField("A"))
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("hello"))
+	b.Reset()
+	require.NoError(t, b.DigField("B"))
+	require.NoError(t, b.SetString("world"))
+
+	assert.Equal(t, []string{"hello"}, x.A)
+	assert.Equal(t, "world", x.B)
+}
+
+func TestSetString(t *testing.T) {
+	x := struct {
+		Field string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	assert.Error(t, b.SetString("oops"))
+	require.NoError(t, b.DigField("Field"))
+	require.NoError(t, b.SetString("hello!"))
+	assert.Equal(t, "hello!", x.Field)
+}
+
+func TestSliceNewElem(t *testing.T) {
+	x := struct {
+		Field []string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	require.NoError(t, b.DigField("Field"))
+	b.Save()
+
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("Val1"))
+	b.Load()
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("Val2"))
+
+	require.Error(t, b.SliceNewElem())
+
+	assert.Equal(t, []string{"Val1", "Val2"}, x.Field)
+}
+
+func TestSliceNewElemNested(t *testing.T) {
+	x := struct {
+		Field [][]string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	require.NoError(t, b.DigField("Field"))
+
+	b.Save()
+
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("Val1.1"))
+	b.Load()
+	b.Save()
+
+	require.NoError(t, b.SliceNewElem())
+	b.Save()
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("Val2.1"))
+	b.Load()
+	require.NoError(t, b.SliceNewElem())
+	require.NoError(t, b.SetString("Val2.2"))
+	b.Load()
+	require.NoError(t, b.SliceNewElem())
+
+	assert.Equal(t, [][]string{{"Val1.1"}, {"Val2.1", "Val2.2"}, nil}, x.Field)
+}
+
+func TestIncorrectKindError(t *testing.T) {
+	err := reflectbuild.IncorrectKindError{
+		Actual:   reflect.String,
+		Expected: reflect.Struct,
+	}
+	assert.NotEmpty(t, err.Error())
+}
+
+func TestFieldNotFoundError(t *testing.T) {
+	err := reflectbuild.FieldNotFoundError{
+		Struct: reflect.ValueOf(struct {
+			Blah string
+		}{}),
+		FieldName: "Foo",
+	}
+	assert.NotEmpty(t, err.Error())
+}
+
+func TestCursor(t *testing.T) {
+	x := struct {
+		Field string
+	}{}
+	b, err := reflectbuild.NewBuilder(&x)
+	require.NoError(t, err)
+	assert.Equal(t, b.Cursor().Kind(), reflect.Struct)
+	require.NoError(t, b.DigField("Field"))
+	assert.Equal(t, b.Cursor().Kind(), reflect.String)
+}

unmarshal.go

@@ -5,30 +5,24 @@ import (
 	"encoding/hex"
 	"fmt"
 	"reflect"
+
+	"github.com/pelletier/go-toml/v2/internal/reflectbuild"
 )
 
 func Unmarshal(data []byte, v interface{}) error {
-	if v == nil {
+	u := &unmarshaler{}
-		return fmt.Errorf("cannot unmarshal to nil target")
+	u.builder, u.err = reflectbuild.NewBuilder(v)
-	}
+	if u.err == nil {
-	rv := reflect.ValueOf(v)
+		parseErr := parser{builder: u}.parse(data)
-	if rv.Kind() != reflect.Ptr {
+		if parseErr != nil {
-		return fmt.Errorf("can only marshal to pointer, not %s", rv.Kind())
+			return parseErr
-	}
+		}
-
-	u := &unmarshaler{stack: []reflect.Value{rv.Elem()}}
-	parseErr := parser{builder: u}.parse(data)
-	if parseErr != nil {
-		return parseErr
 	}
 	return u.err
 }
 
 type unmarshaler struct {
-	// Each stack frame is a pointer to the root object that should be
+	builder reflectbuild.Builder
-	// considered when settings values.
-	// It at least contains the root object passed to Unmarshal.
-	stack []reflect.Value
 
 	// First error that appeared during the construction of the object.
 	// When set all callbacks are no-ops.
@@ -41,6 +35,35 @@ type unmarshaler struct {
 	// Table Arrays need a buffer of keys because we need to know which one is
 	// the last one, as it may result in creating a new element in the array.
 	arrayTableKey [][]byte
+
+	// Flag to indicate that the next value is an an assignment.
+	// Assignments are when the builder already points to the value, and should
+	// be directly assigned. This is used to distinguish between assigning or
+	// appending to arrays.
+	assign bool
+}
+
+func (u *unmarshaler) Assignation() {
+	u.assign = true
+}
+
+func (u *unmarshaler) ArrayBegin() {
+	if u.err != nil {
+		return
+	}
+	u.builder.Save()
+	if u.assign {
+		u.assign = false
+	} else {
+		u.builder.SliceNewElem()
+	}
+}
+
+func (u *unmarshaler) ArrayEnd() {
+	if u.err != nil {
+		return
+	}
+	u.builder.Load()
 }
 
 func (u *unmarshaler) ArrayTableBegin() {
@@ -56,99 +79,48 @@ func (u *unmarshaler) ArrayTableEnd() {
 		return
 	}
 
-	u.parsingTableArray = false
+	u.builder.Reset()
 
-	u.stack = u.stack[:1]
+	for _, v := range u.arrayTableKey[:len(u.arrayTableKey)-1] {
-
+		u.err = u.builder.DigField(string(v))
-	parent := u.top()
+		if u.err != nil {
-	for _, k := range u.arrayTableKey {
-		switch parent.Type().Kind() {
-		case reflect.Slice:
-			l := parent.Len()
-			parent = parent.Index(l - 1)
-		case reflect.Struct:
-		default:
-			u.err = fmt.Errorf("value of type '%s' cannot have children", parent)
 			return
 		}
-
+		u.err = u.builder.SliceLastOrCreate()
-		f := parent.FieldByName(string(k))
-		if !f.IsValid() {
-			// TODO: implement alternative names
-			u.err = fmt.Errorf("field '%s' not found", string(k))
-			return
-		}
-		parent = f
 	}
 
-	if parent.Type().Kind() != reflect.Slice {
+	v := u.arrayTableKey[len(u.arrayTableKey)-1]
-		u.err = fmt.Errorf("array table key is not a slice")
+	u.err = u.builder.DigField(string(v))
+	if u.err != nil {
 		return
 	}
+	u.err = u.builder.SliceNewElem()
 
-	n := reflect.New(parent.Type().Elem())
+	u.parsingTableArray = false
-	parent.Set(reflect.Append(parent, n.Elem()))
-	last := parent.Index(parent.Len() - 1)
-	u.push(last)
 	u.arrayTableKey = u.arrayTableKey[:0]
 }
 
 func (u *unmarshaler) KeyValBegin() {
-	u.push(u.top())
+	u.builder.Save()
 }
 
 func (u *unmarshaler) KeyValEnd() {
-	u.pop()
+	u.builder.Load()
-}
-
-func (u *unmarshaler) getOrCreateChild(key string) (reflect.Value, error) {
-	parent := u.top()
-	switch parent.Type().Kind() {
-	case reflect.Slice:
-		l := parent.Len()
-		parent = parent.Index(l - 1)
-	case reflect.Struct:
-	default:
-		return reflect.Value{}, fmt.Errorf("value of type '%s' cannot have children", parent)
-	}
-
-	f := parent.FieldByName(key)
-	if !f.IsValid() {
-		// TODO: implement alternative names
-		return reflect.Value{}, fmt.Errorf("field '%s' not found", key)
-	}
-	// TODO create things
-	return f, nil
-}
-
-func (u *unmarshaler) top() reflect.Value {
-	return u.stack[len(u.stack)-1]
-}
-
-func (u *unmarshaler) push(v reflect.Value) {
-	u.stack = append(u.stack, v)
-}
-
-func (u *unmarshaler) pop() {
-	u.stack = u.stack[:len(u.stack)-1]
-}
-
-func (u *unmarshaler) replace(v reflect.Value) {
-	u.stack[len(u.stack)-1] = v
 }
 
 func (u *unmarshaler) StringValue(v []byte) {
 	if u.err != nil {
 		return
 	}
-
+	if u.builder.IsSlice() {
-	t := u.top()
+		u.builder.Save()
-	if t.Type().Kind() == reflect.Slice {
+		u.err = u.builder.SliceAppend(reflect.ValueOf(string(v)))
-		s := reflect.ValueOf(string(v))
+		if u.err != nil {
-		n := reflect.Append(t, s)
+			return
-		t.Set(n)
+		}
+		u.builder.Load()
 	} else {
-		u.top().SetString(string(v))
+		u.err = u.builder.SetString(string(v))
 	}
 }
 
@@ -156,14 +128,15 @@ func (u *unmarshaler) BoolValue(b bool) {
 	if u.err != nil {
 		return
 	}
-
+	if u.builder.IsSlice() {
-	t := u.top()
+		u.builder.Save()
-	if t.Type().Kind() == reflect.Slice {
+		u.err = u.builder.SliceAppend(reflect.ValueOf(b))
-		s := reflect.ValueOf(b)
+		if u.err != nil {
-		n := reflect.Append(t, s)
+			return
-		t.Set(n)
+		}
+		u.builder.Load()
 	} else {
-		u.top().SetBool(b)
+		u.err = u.builder.SetBool(b)
 	}
 }
 
@@ -175,12 +148,13 @@ func (u *unmarshaler) SimpleKey(v []byte) {
 	if u.parsingTableArray {
 		u.arrayTableKey = append(u.arrayTableKey, v)
 	} else {
-		target, err := u.getOrCreateChild(string(v))
+		if u.builder.Cursor().Kind() == reflect.Slice {
-		if err != nil {
+			u.err = u.builder.SliceLastOrCreate()
-			u.err = err
+			if u.err != nil {
-			return
+				return
+			}
 		}
-		u.replace(target)
+		u.err = u.builder.DigField(string(v))
 	}
 }
 
@@ -190,9 +164,7 @@ func (u *unmarshaler) StandardTableBegin() {
 	}
 
 	// tables are only top-level
-	u.stack = u.stack[:1]
+	u.builder.Reset()
-
-	u.push(u.top())
 }
 
 func (u *unmarshaler) StandardTableEnd() {
@@ -210,6 +182,9 @@ type builder interface {
 	ArrayTableEnd()
 	KeyValBegin()
 	KeyValEnd()
+	ArrayBegin()
+	ArrayEnd()
+	Assignation()
 
 	StringValue(v []byte)
 	BoolValue(b bool)
@@ -355,6 +330,7 @@ func (p parser) parseKeyval(b []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	p.builder.Assignation()
 	b = p.parseWhitespace(b)
 
 	return p.parseVal(b)
@@ -471,6 +447,9 @@ func (p parser) parseValArray(b []byte) ([]byte, error) {
 	//array-sep = %x2C  ; , Comma
 	//ws-comment-newline = *( wschar / [ comment ] newline )
 
+	p.builder.ArrayBegin()
+	defer p.builder.ArrayEnd()
+
 	b = b[1:]
 
 	first := true

unmarshal_test.go

@@ -245,6 +245,42 @@ func TestArraySimple(t *testing.T) {
 	assert.Equal(t, []string{"hello", "world"}, x.Foo)
 }
 
+func TestArrayNestedInTable(t *testing.T) {
+	x := struct {
+		Wrapper struct {
+			Foo []string
+		}
+	}{}
+	doc := `[Wrapper]
+Foo = ["hello", "world"]`
+	err := toml.Unmarshal([]byte(doc), &x)
+	require.NoError(t, err)
+	assert.Equal(t, []string{"hello", "world"}, x.Wrapper.Foo)
+}
+
+func TestArrayMixed(t *testing.T) {
+	x := struct {
+		Wrapper struct {
+			Foo []interface{}
+		}
+	}{}
+	doc := `[Wrapper]
+Foo = ["hello", true]`
+	err := toml.Unmarshal([]byte(doc), &x)
+	require.NoError(t, err)
+	assert.Equal(t, []interface{}{"hello", true}, x.Wrapper.Foo)
+}
+
+func TestArrayNested(t *testing.T) {
+	x := struct {
+		Foo [][]string
+	}{}
+	doc := `Foo = [["hello", "world"], ["a"], []]`
+	err := toml.Unmarshal([]byte(doc), &x)
+	require.NoError(t, err)
+	assert.Equal(t, [][]string{{"hello", "world"}, {"a"}, nil}, x.Foo)
+}
+
 func TestBool(t *testing.T) {
 	x := struct {
 		Truthy bool