Decoding error position tracking

README.md

@@ -17,7 +17,7 @@ Development branch. Probably does not work.
 - [x] Benchmark!
 - [x] Abstract AST.
 - [x] Original go-toml testgen tests pass.
-- [ ] Track file position (line, column) for errors.
+- [x] Track file position (line, column) for errors.
 - [ ] Attach comments to AST (gated by parser flag).
 - [ ] Benchmark again!
 

decode.go

@@ -34,7 +34,7 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 	date := LocalDate{}
 
 	if len(b) != 10 || b[4] != '-' || b[7] != '-' {
-		return date, fmt.Errorf("dates are expected to have the format YYYY-MM-DD")
+		return date, newDecodeError(b, "dates are expected to have the format YYYY-MM-DD")
 	}
 
 	var err error
@@ -89,7 +89,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 		zone = time.UTC
 	} else {
 		if len(b) != 6 {
-			return time.Time{}, fmt.Errorf("invalid date-time timezone")
+			return time.Time{}, newDecodeError(b, "invalid date-time timezone")
 		}
 		direction := 1
 		switch b[0] {
@@ -97,7 +97,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 		case '-':
 			direction = -1
 		default:
-			return time.Time{}, fmt.Errorf("invalid timezone offset character")
+			return time.Time{}, newDecodeError(b[0:1], "invalid timezone offset character")
 		}
 
 		hours := digitsToInt(b[1:3])
@@ -107,7 +107,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 	}
 
 	if len(b) > 0 {
-		return time.Time{}, fmt.Errorf("extra bytes at the end of the timezone")
+		return time.Time{}, newDecodeError(b, "extra bytes at the end of the timezone")
 	}
 
 	t := time.Date(
@@ -166,14 +166,14 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, err
 	}
 	if b[2] != ':' {
-		return t, nil, fmt.Errorf("expecting colon between hours and minutes")
+		return t, nil, newDecodeError(b[2:3], "expecting colon between hours and minutes")
 	}
 	t.Minute, err = parseDecimalDigits(b[3:5])
 	if err != nil {
 		return t, nil, err
 	}
 	if b[5] != ':' {
-		return t, nil, fmt.Errorf("expecting colon between minutes and seconds")
+		return t, nil, newDecodeError(b[5:6], "expecting colon between minutes and seconds")
 	}
 	t.Second, err = parseDecimalDigits(b[6:8])
 	if err != nil {

errors.go

@@ -129,8 +129,16 @@ func formatLineNumber(line int, width int) string {
 func linesOfContext(document []byte, highlight []byte, offset int, linesAround int) ([][]byte, [][]byte) {
 	var beforeLines [][]byte
 	for beforeOffset, lastOffset := offset, offset; beforeOffset >= 0 && len(beforeLines) <= linesAround; beforeOffset-- {
+		if beforeOffset == len(document) {
+			beforeLines = append(beforeLines, []byte{})
+			continue
+		}
 		if document[beforeOffset] == '\n' {
+			if beforeOffset == lastOffset {
+				beforeLines = append(beforeLines, []byte{})
+			} else {
 				beforeLines = append(beforeLines, document[beforeOffset+1:lastOffset])
+			}
 			lastOffset = beforeOffset
 		} else if beforeOffset == 0 && beforeOffset != lastOffset {
 			beforeLines = append(beforeLines, document[beforeOffset:lastOffset])

internal/unsafe/unsafe.go

@@ -23,7 +23,7 @@ func SubsliceOffset(data []byte, subslice []byte) int {
 
 	intoffset := int(offset)
 
-	if intoffset >= datap.Len {
+	if intoffset > datap.Len {
 		panic(fmt.Errorf("slice offset (%d) is farther than data length (%d)", intoffset, datap.Len))
 	}
 

parser.go

@@ -363,7 +363,7 @@ func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
 		}
 
 		if len(b) == 0 {
-			return parent, nil, unexpectedCharacter{b: b}
+			return parent, nil, unexpectedCharacter{b: b} // TODO: should be unexpected EOF
 		}
 
 		if b[0] == ']' {
@@ -590,7 +590,7 @@ func (p *parser) parseSimpleKey(b []byte) (key, rest []byte, err error) {
 	//quoted-key = basic-string / literal-string
 
 	if len(b) == 0 {
-		return nil, nil, unexpectedCharacter{b: b}
+		return nil, nil, unexpectedCharacter{b: b} // TODO: should be unexpected EOF
 	}
 
 	if b[0] == '\'' {
@@ -600,7 +600,7 @@ func (p *parser) parseSimpleKey(b []byte) (key, rest []byte, err error) {
 	} else if isUnquotedKeyChar(b[0]) {
 		key, rest, err = scanUnquotedKey(b)
 	} else {
-		err = unexpectedCharacter{b: b}
+		err = unexpectedCharacter{b: b} // TODO: should contain expected characters
 	}
 	return
 }
@@ -1158,8 +1158,11 @@ func isValidBinaryRune(r byte) bool {
 }
 
 func expect(x byte, b []byte) ([]byte, error) {
-	if len(b) == 0 || b[0] != x {
-		return nil, unexpectedCharacter{r: x, b: b}
+	if len(b) == 0 {
+		return nil, newDecodeError(b[:0], "expecting %#U", x)
+	}
+	if b[0] != x {
+		return nil, newDecodeError(b[0:1], "expected character %U", x)
 	}
 	return b[1:], nil
 }

scanner.go

@@ -30,7 +30,7 @@ func scanUnquotedKey(b []byte) ([]byte, []byte, error) {
 			return b[:i], b[i:], nil
 		}
 	}
-	return b, nil, nil
+	return b, b[len(b):], nil
 }
 
 func isUnquotedKeyChar(r byte) bool {
@@ -46,10 +46,10 @@ func scanLiteralString(b []byte) ([]byte, []byte, error) {
 		case '\'':
 			return b[:i+1], b[i+1:], nil
 		case '\n':
-			return nil, nil, fmt.Errorf("literal strings cannot have new lines")
+			return nil, nil, newDecodeError(b[i:i+1], "literal strings cannot have new lines")
 		}
 	}
-	return nil, nil, fmt.Errorf("unterminated literal string")
+	return nil, nil, newDecodeError(b[len(b):], "unterminated literal string")
 }
 
 func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
@@ -70,7 +70,7 @@ func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
 		}
 	}
 
-	return nil, nil, fmt.Errorf(`multiline literal string not terminated by '''`)
+	return nil, nil, newDecodeError(b[len(b):], `multiline literal string not terminated by '''`)
 }
 
 func scanWindowsNewline(b []byte) ([]byte, []byte, error) {
@@ -92,7 +92,7 @@ func scanWhitespace(b []byte) ([]byte, []byte) {
 			return b[:i], b[i:]
 		}
 	}
-	return b, nil
+	return b, b[len(b):]
 }
 
 func scanComment(b []byte) ([]byte, []byte, error) {
@@ -125,10 +125,10 @@ func scanBasicString(b []byte) ([]byte, []byte, error) {
 		case '"':
 			return b[:i+1], b[i+1:], nil
 		case '\n':
-			return nil, nil, fmt.Errorf("basic strings cannot have new lines")
+			return nil, nil, newDecodeError(b[i:i+1], "basic strings cannot have new lines")
 		case '\\':
 			if len(b) < i+2 {
-				return nil, nil, fmt.Errorf("need a character after \\")
+				return nil, nil, newDecodeError(b[i:i+1], "need a character after \\")
 			}
 			i++ // skip the next character
 		}
@@ -158,11 +158,11 @@ func scanMultilineBasicString(b []byte) ([]byte, []byte, error) {
 			}
 		case '\\':
 			if len(b) < i+2 {
-				return nil, nil, fmt.Errorf("need a character after \\")
+				return nil, nil, newDecodeError(b[len(b):], "need a character after \\")
 			}
 			i++ // skip the next character
 		}
 	}
 
-	return nil, nil, fmt.Errorf(`multiline basic string not terminated by """`)
+	return nil, nil, newDecodeError(b[len(b):], `multiline basic string not terminated by """`)
 }

unmarshaler.go

@@ -268,11 +268,22 @@ func (d *decoder) unmarshalValue(x target, node ast.Node) error {
 		return unmarshalLocalDateTime(x, node)
 	case ast.DateTime:
 		return unmarshalDateTime(x, node)
+	case ast.LocalDate:
+		return unmarshalLocalDate(x, node)
 	default:
 		panic(fmt.Errorf("unhandled unmarshalValue kind %s", node.Kind))
 	}
 }
 
+func unmarshalLocalDate(x target, node ast.Node) error {
+	assertNode(ast.LocalDate, node)
+	v, err := parseLocalDate(node.Data)
+	if err != nil {
+		return err
+	}
+	return setDate(x, v)
+}
+
 func unmarshalLocalDateTime(x target, node ast.Node) error {
 	assertNode(ast.LocalDateTime, node)
 	v, rest, err := parseLocalDateTime(node.Data)
@@ -280,7 +291,7 @@ func unmarshalLocalDateTime(x target, node ast.Node) error {
 		return err
 	}
 	if len(rest) > 0 {
-		return fmt.Errorf("extra characters at the end of a local date time")
+		return newDecodeError(rest, "extra characters at the end of a local date time")
 	}
 	return setLocalDateTime(x, v)
 }
@@ -302,6 +313,10 @@ func setDateTime(x target, v time.Time) error {
 	return x.set(reflect.ValueOf(v))
 }
 
+func setDate(x target, v LocalDate) error {
+	return x.set(reflect.ValueOf(v))
+}
+
 func unmarshalString(x target, node ast.Node) error {
 	assertNode(ast.String, node)
 	return setString(x, string(node.Data))

unmarshaler_test.go

@@ -705,7 +705,6 @@ B = "data"`,
 	}
 }
 
-
 type Integer484 struct {
 	Value int
 }
@@ -760,3 +759,94 @@ version = "0.1.0"`)
 	}
 	assert.Equal(t, expected, a)
 }
+
+func TestUnmarshalDecodeErrors(t *testing.T) {
+	examples := []struct {
+		desc string
+		data string
+		msg  string
+	}{
+		{
+			desc: "int with wrong base",
+			data: `a = 0f2`,
+		},
+		{
+			desc: "literal string with new lines",
+			data: `a = 'hello
+world'`,
+			msg: `literal strings cannot have new lines`,
+		},
+		{
+			desc: "unterminated literal string",
+			data: `a = 'hello`,
+			msg:  `unterminated literal string`,
+		},
+		{
+			desc: "unterminated multiline literal string",
+			data: `a = '''hello`,
+			msg:  `multiline literal string not terminated by '''`,
+		},
+		{
+			desc: "basic string with new lines",
+			data: `a = "hello
+"`,
+			msg: `basic strings cannot have new lines`,
+		},
+		{
+			desc: "basic string with unfinished escape",
+			data: `a = "hello \`,
+			msg:  `need a character after \`,
+		},
+		{
+			desc: "basic unfinished multiline string",
+			data: `a = """hello`,
+			msg:  `multiline basic string not terminated by """`,
+		},
+		{
+			desc: "basic unfinished escape in multiline string",
+			data: `a = """hello \`,
+			msg:  `need a character after \`,
+		},
+		{
+			desc: "malformed local date",
+			data: `a = 2021-033-0`,
+			msg:  `dates are expected to have the format YYYY-MM-DD`,
+		},
+		{
+			desc: "malformed tz",
+			data: `a = 2021-03-30 21:31:00+1`,
+			msg:  `invalid date-time timezone`,
+		},
+		{
+			desc: "malformed tz first char",
+			data: `a = 2021-03-30 21:31:00:1`,
+			msg:  `extra characters at the end of a local date time`,
+		},
+		{
+			desc: "bad char between hours and minutes",
+			data: `a = 2021-03-30 213:1:00`,
+			msg:  `expecting colon between hours and minutes`,
+		},
+		{
+			desc: "bad char between minutes and seconds",
+			data: `a = 2021-03-30 21:312:0`,
+			msg:  `expecting colon between minutes and seconds`,
+		},
+	}
+
+	for _, e := range examples {
+		t.Run(e.desc, func(t *testing.T) {
+			m := map[string]interface{}{}
+			err := toml.Unmarshal([]byte(e.data), &m)
+			require.Error(t, err)
+			de, ok := err.(*toml.DecodeError)
+			if !ok {
+				t.Fatalf("err should have been a *toml.DecodeError, but got %s (%T)", err, err)
+			}
+			if e.msg != "" {
+				t.Log("\n" + de.String())
+				require.Equal(t, e.msg, de.Error())
+			}
+		})
+	}
+}