fix: wrap the error that came back from the callback (#674) (#675)

openapi3/schema.go

@@ -1298,29 +1298,31 @@ func (schema *Schema) visitJSONString(settings *schemaValidationSettings, value
 	}
 
 	// "format"
-	var formatErr string
+	var formatStrErr string
+	var formatErr error
 	if format := schema.Format; format != "" {
 		if f, ok := SchemaStringFormats[format]; ok {
 			switch {
 			case f.regexp != nil && f.callback == nil:
 				if cp := f.regexp; !cp.MatchString(value) {
-					formatErr = fmt.Sprintf(`string doesn't match the format %q (regular expression "%s")`, format, cp.String())
+					formatStrErr = fmt.Sprintf(`string doesn't match the format %q (regular expression "%s")`, format, cp.String())
 				}
 			case f.regexp == nil && f.callback != nil:
 				if err := f.callback(value); err != nil {
-					formatErr = err.Error()
+					formatErr = err
 				}
 			default:
-				formatErr = fmt.Sprintf("corrupted entry %q in SchemaStringFormats", format)
+				formatStrErr = fmt.Sprintf("corrupted entry %q in SchemaStringFormats", format)
 			}
 		}
 	}
-	if formatErr != "" {
+	if formatStrErr != "" || formatErr != nil {
 		err := &SchemaError{
 			Value:       value,
 			Schema:      schema,
 			SchemaField: "format",
-			Reason:      formatErr,
+			Reason:      formatStrErr,
+			Origin:      formatErr,
 		}
 		if !settings.multiError {
 			return err

openapi3/schema_formats_test.go

@@ -2,8 +2,10 @@ package openapi3
 
 import (
 	"context"
+	"errors"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -58,3 +60,18 @@ func TestIssue430(t *testing.T) {
 		}
 	}
 }
+
+func TestFormatCallback_WrapError(t *testing.T) {
+	var errSomething = errors.New("something error")
+
+	DefineStringFormatCallback("foobar", func(value string) error {
+		return errSomething
+	})
+
+	s := &Schema{Format: "foobar"}
+	err := s.VisitJSONString("blablabla")
+
+	assert.ErrorIs(t, err, errSomething)
+
+	delete(SchemaStringFormats, "foobar")
+}