Merge pull request #105 from go-viper/error-refactor

sagikazarmark · web-flow · commit 36de1e1d74f5 · 2025-06-16T15:44:20.000+02:00
feat: add common error interface
diff --git a/errors.go b/errors.go
@@ -5,6 +5,15 @@ import (
 	"reflect"
 )
 
+// Error interface is implemented by all errors emitted by mapstructure.
+//
+// Use [errors.As] to check if an error implements this interface.
+type Error interface {
+	error
+
+	mapstructure()
+}
+
 // DecodeError is a generic error type that holds information about
 // a decoding error together with the name of the field that caused the error.
 type DecodeError struct {
@@ -31,27 +40,35 @@ func (e *DecodeError) Error() string {
 	return fmt.Sprintf("'%s' %s", e.name, e.err)
 }
 
+func (*DecodeError) mapstructure() {}
+
 // ParseError is an error type that indicates a value could not be parsed
 // into the expected type.
 type ParseError struct {
 	Expected reflect.Value
-	Value    interface{}
+	Value    any
 	Err      error
 }
 
 func (e *ParseError) Error() string {
-	return fmt.Sprintf("cannot parse '%s' as '%s': %s",
-		e.Value, e.Expected.Type(), e.Err)
+	return fmt.Sprintf("cannot parse value as '%s': %s", e.Expected.Type(), e.Err)
 }
 
+func (*ParseError) mapstructure() {}
+
 // UnconvertibleTypeError is an error type that indicates a value could not be
 // converted to the expected type.
 type UnconvertibleTypeError struct {
 	Expected reflect.Value
-	Value    interface{}
+	Value    any
 }
 
 func (e *UnconvertibleTypeError) Error() string {
-	return fmt.Sprintf("expected type '%s', got unconvertible type '%s', value: '%v'",
-		e.Expected.Type(), reflect.TypeOf(e.Value), e.Value)
+	return fmt.Sprintf(
+		"expected type '%s', got unconvertible type '%s'",
+		e.Expected.Type(),
+		reflect.TypeOf(e.Value),
+	)
 }
+
+func (*UnconvertibleTypeError) mapstructure() {}
diff --git a/mapstructure_examples_test.go b/mapstructure_examples_test.go
@@ -65,11 +65,11 @@ func ExampleDecode_errors() {
 	// Output:
 	// decoding failed due to the following error(s):
 	//
-	// 'Name' expected type 'string', got unconvertible type 'int', value: '123'
-	// 'Age' expected type 'int', got unconvertible type 'string', value: 'bad value'
-	// 'Emails[0]' expected type 'string', got unconvertible type 'int', value: '1'
-	// 'Emails[1]' expected type 'string', got unconvertible type 'int', value: '2'
-	// 'Emails[2]' expected type 'string', got unconvertible type 'int', value: '3'
+	// 'Name' expected type 'string', got unconvertible type 'int'
+	// 'Age' expected type 'int', got unconvertible type 'string'
+	// 'Emails[0]' expected type 'string', got unconvertible type 'int'
+	// 'Emails[1]' expected type 'string', got unconvertible type 'int'
+	// 'Emails[2]' expected type 'string', got unconvertible type 'int'
 }
 
 func ExampleDecode_metadata() {
