pkg/config: fix line numbers shown incorrectly for TOML type mismatch errors (#5195)

pkg/config/load.go

@@ -180,24 +180,26 @@ func LoadConfigure(b []byte, c any, strict bool, formats ...string) error {
 	}
 
 	originalBytes := b
+	parsedFromTOML := false
 
 	var tomlObj any
 	tomlErr := toml.Unmarshal(b, &tomlObj)
 	if tomlErr == nil {
+		parsedFromTOML = true
 		var err error
 		b, err = jsonx.Marshal(&tomlObj)
 		if err != nil {
 			return err
 		}
 	} else if format == "toml" {
-		// File is known to be TOML but has syntax errors — report with line/column info.
+		// File is known to be TOML but has syntax errors.
 		return formatTOMLError(tomlErr)
 	}
 
 	// If the buffer smells like JSON (first non-whitespace character is '{'), unmarshal as JSON directly.
 	if yaml.IsJSONBuffer(b) {
 		if err := decodeJSONContent(b, c, strict); err != nil {
-			return enhanceDecodeError(err, originalBytes)
+			return enhanceDecodeError(err, originalBytes, !parsedFromTOML)
 		}
 		return nil
 	}
@@ -206,7 +208,7 @@ func LoadConfigure(b []byte, c any, strict bool, formats ...string) error {
 	if strict {
 		// In strict mode, always use our custom handler to support YAML merge
 		if err := parseYAMLWithDotFieldsHandling(b, c); err != nil {
-			return enhanceDecodeError(err, originalBytes)
+			return enhanceDecodeError(err, originalBytes, !parsedFromTOML)
 		}
 		return nil
 	}
@@ -223,18 +225,20 @@ func formatTOMLError(err error) error {
 	}
 	var strictErr *toml.StrictMissingError
 	if errors.As(err, &strictErr) {
-		return fmt.Errorf("toml: %s", strictErr.Error())
+		return strictErr
 	}
 	return err
 }
 
 // enhanceDecodeError tries to add field path and line number information to JSON/YAML decode errors.
-func enhanceDecodeError(err error, originalContent []byte) error {
+func enhanceDecodeError(err error, originalContent []byte, includeLine bool) error {
 	var typeErr *json.UnmarshalTypeError
 	if errors.As(err, &typeErr) && typeErr.Field != "" {
-		line := findFieldLineInContent(originalContent, typeErr.Field)
+		if includeLine {
-		if line > 0 {
+			line := findFieldLineInContent(originalContent, typeErr.Field)
-			return fmt.Errorf("line %d: field \"%s\": cannot unmarshal %s into %s", line, typeErr.Field, typeErr.Value, typeErr.Type)
+			if line > 0 {
+				return fmt.Errorf("line %d: field \"%s\": cannot unmarshal %s into %s", line, typeErr.Field, typeErr.Value, typeErr.Type)
+			}
 		}
 		return fmt.Errorf("field \"%s\": cannot unmarshal %s into %s", typeErr.Field, typeErr.Value, typeErr.Type)
 	}
@@ -244,6 +248,10 @@ func enhanceDecodeError(err error, originalContent []byte) error {
 // findFieldLineInContent searches the original config content for a field name
 // and returns the 1-indexed line number where it appears, or 0 if not found.
 func findFieldLineInContent(content []byte, fieldPath string) int {
+	if fieldPath == "" {
+		return 0
+	}
+
 	// Use the last component of the field path (e.g. "proxies" from "proxies" or
 	// "protocol" from "transport.protocol").
 	parts := strings.Split(fieldPath, ".")

pkg/config/load_test.go

@@ -496,7 +496,7 @@ serverPort: 7000
 	require.Equal(7000, clientCfg.ServerPort)
 }
 
-func TestTOMLSyntaxErrorWithLineNumber(t *testing.T) {
+func TestTOMLSyntaxErrorWithPosition(t *testing.T) {
 	require := require.New(t)
 
 	// TOML with syntax error (unclosed table array header)
@@ -510,8 +510,9 @@ name = "test"
 	clientCfg := v1.ClientConfig{}
 	err := LoadConfigure([]byte(content), &clientCfg, false, "toml")
 	require.Error(err)
-	require.Contains(err.Error(), "line")
 	require.Contains(err.Error(), "toml")
+	require.Contains(err.Error(), "line")
+	require.Contains(err.Error(), "column")
 }
 
 func TestTOMLTypeMismatchErrorWithFieldInfo(t *testing.T) {
@@ -529,6 +530,7 @@ proxies = "this should be a table array"
 	// The error should contain field info
 	errMsg := err.Error()
 	require.Contains(errMsg, "proxies")
+	require.NotContains(errMsg, "line")
 }
 
 func TestFindFieldLineInContent(t *testing.T) {