feat: Expose syntax and type errors (#1)

Ref: goccy#424

decode.go

@@ -534,6 +534,10 @@ func (e *unknownFieldError) Error() string {
 	return e.err.Error()
 }
 
+func (e *unknownFieldError) Unwrap() error {
+	return e.err
+}
+
 func errUnknownField(msg string, tk *token.Token) *unknownFieldError {
 	return &unknownFieldError{err: errors.ErrSyntax(msg, tk)}
 }
@@ -550,6 +554,10 @@ func (e *duplicateKeyError) Error() string {
 	return e.err.Error()
 }
 
+func (e *duplicateKeyError) Unwrap() error {
+	return e.err
+}
+
 func errDuplicateKey(msg string, tk *token.Token) *duplicateKeyError {
 	return &duplicateKeyError{err: errors.ErrSyntax(msg, tk)}
 }

error.go

@@ -2,6 +2,8 @@ package yaml
 
 import (
 	"github.com/goccy/go-yaml/ast"
+	"github.com/goccy/go-yaml/internal/errors"
+	"github.com/goccy/go-yaml/token"
 	"golang.org/x/xerrors"
 )
 
@@ -60,3 +62,42 @@ func IsInvalidAnchorNameError(err error) bool {
 func IsInvalidAliasNameError(err error) bool {
 	return xerrors.Is(err, ast.ErrInvalidAliasName)
 }
+
+// TokenScopedError represents an error associated with a specific [token.Token].
+type TokenScopedError struct {
+	// Msg is the underlying error message.
+	Msg string
+	// Token is the [token.Token] associated with this error.
+	Token *token.Token
+	// err is the underlying, unwraped error.
+	err error
+}
+
+// Error implements the error interface.
+// It returns the unwraped error returned by go-yaml.
+func (s TokenScopedError) Error() string {
+	return s.err.Error()
+}
+
+// AsTokenScopedError checks if the error is associated with a specific token.
+// If so, it returns
+// Otherwise, it returns nil.
+func AsTokenScopedError(err error) *TokenScopedError {
+	var syntaxError *errors.SyntaxError
+	if xerrors.As(err, &syntaxError) {
+		return &TokenScopedError{
+			Msg:   syntaxError.GetMessage(),
+			Token: syntaxError.GetToken(),
+			err:   err,
+		}
+	}
+	var typeError *errors.TypeError
+	if xerrors.As(err, &typeError) {
+		return &TokenScopedError{
+			Msg:   typeError.Error(),
+			Token: typeError.Token,
+			err:   err,
+		}
+	}
+	return nil
+}

error_test.go

@@ -0,0 +1,78 @@
+package yaml
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/goccy/go-yaml/internal/errors"
+	"github.com/goccy/go-yaml/token"
+	"golang.org/x/xerrors"
+)
+
+func TestAsSyntaxError(t *testing.T) {
+	tests := []struct {
+		input    error
+		expected *TokenScopedError
+	}{
+		{
+			input:    nil,
+			expected: nil,
+		},
+		{
+			input:    xerrors.New("dummy test"),
+			expected: nil,
+		},
+		{
+			input: errors.ErrSyntax("some error", &token.Token{Value: "123"}),
+			expected: &TokenScopedError{
+				Msg:   "some error",
+				Token: &token.Token{Value: "123"},
+			},
+		},
+		{
+			input: xerrors.Errorf(
+				"something went wrong: %w",
+				errors.ErrSyntax("some error", &token.Token{Value: "123"})),
+			expected: &TokenScopedError{
+				Msg:   "some error",
+				Token: &token.Token{Value: "123"},
+			},
+		},
+		{
+			input: errUnknownField("unknown field", &token.Token{Value: "123"}),
+			expected: &TokenScopedError{
+				Msg:   "unknown field",
+				Token: &token.Token{Value: "123"},
+			},
+		},
+		{
+			input: errDuplicateKey("duplicate key", &token.Token{Value: "123"}),
+			expected: &TokenScopedError{
+				Msg:   "duplicate key",
+				Token: &token.Token{Value: "123"},
+			},
+		},
+		{
+			input: errTypeMismatch(reflect.TypeOf("string"), reflect.TypeOf(0), &token.Token{Value: "123"}),
+			expected: &TokenScopedError{
+				Msg:   "cannot unmarshal int into Go value of type string",
+				Token: &token.Token{Value: "123"},
+			},
+		},
+	}
+	for _, test := range tests {
+		syntaxErr := AsTokenScopedError(test.input)
+		if test.expected == nil {
+			if syntaxErr != nil {
+				t.Fatalf("wanted nil, but go %v", syntaxErr)
+			}
+			continue
+		}
+		if syntaxErr == nil {
+			t.Fatalf("must not be nil")
+		}
+		if *test.expected.Token != *syntaxErr.Token || test.expected.Msg != syntaxErr.Msg {
+			t.Fatalf("unexpected output.\nexpect:\n[%v]\nactual:\n[%v]", test.expected, syntaxErr)
+		}
+	}
+}

internal/errors/error.go

@@ -30,8 +30,8 @@ func Wrapf(err error, msg string, args ...interface{}) error {
 }
 
 // ErrSyntax create syntax error instance with message and token
-func ErrSyntax(msg string, tk *token.Token) *syntaxError {
-	return &syntaxError{
+func ErrSyntax(msg string, tk *token.Token) *SyntaxError {
+	return &SyntaxError{
 		baseError: &baseError{},
 		msg:       msg,
 		token:     tk,
@@ -54,7 +54,7 @@ func (e *baseError) chainStateAndVerb(err error) {
 		wrapErr.state = e.state
 		wrapErr.verb = e.verb
 	}
-	syntaxErr, ok := err.(*syntaxError)
+	syntaxErr, ok := err.(*SyntaxError)
 	if ok {
 		syntaxErr.state = e.state
 		syntaxErr.verb = e.verb
@@ -164,18 +164,18 @@ func (e *wrapError) Error() string {
 	return buf.String()
 }
 
-type syntaxError struct {
+type SyntaxError struct {
 	*baseError
 	msg   string
 	token *token.Token
 	frame xerrors.Frame
 }
 
-func (e *syntaxError) PrettyPrint(p xerrors.Printer, colored, inclSource bool) error {
+func (e *SyntaxError) PrettyPrint(p xerrors.Printer, colored, inclSource bool) error {
 	return e.FormatError(&FormatErrorPrinter{Printer: p, Colored: colored, InclSource: inclSource})
 }
 
-func (e *syntaxError) FormatError(p xerrors.Printer) error {
+func (e *SyntaxError) FormatError(p xerrors.Printer) error {
 	var pp printer.Printer
 
 	var colored, inclSource bool
@@ -199,6 +199,14 @@ func (e *syntaxError) FormatError(p xerrors.Printer) error {
 	return nil
 }
 
+func (e *SyntaxError) GetToken() *token.Token {
+	return e.token
+}
+
+func (e *SyntaxError) GetMessage() string {
+	return e.msg
+}
+
 type PrettyPrinter interface {
 	PrettyPrint(xerrors.Printer, bool, bool) error
 }
@@ -216,7 +224,7 @@ func (es *Sink) Detail() bool {
 	return false
 }
 
-func (e *syntaxError) Error() string {
+func (e *SyntaxError) Error() string {
 	var buf bytes.Buffer
 	e.PrettyPrint(&Sink{&buf}, defaultColorize, defaultIncludeSource)
 	return buf.String()