openapi3: keep oneOf context in markSchemaErrorKey (#940)

openapi3/schema.go

@@ -2119,14 +2119,16 @@ type SchemaError struct {
 var _ interface{ Unwrap() error } = SchemaError{}
 
 func markSchemaErrorKey(err error, key string) error {
-	var me multiErrorForOneOf
-
-	if errors.As(err, &me) {
-		err = me.Unwrap()
-	}
 
 	if v, ok := err.(*SchemaError); ok {
 		v.reversePath = append(v.reversePath, key)
+		if v.Origin != nil {
+			if unwrapped := errors.Unwrap(v.Origin); unwrapped != nil {
+				if me, ok := unwrapped.(multiErrorForOneOf); ok {
+					_ = markSchemaErrorKey(MultiError(me), key)
+				}
+			}
+		}
 		return v
 	}
 	if v, ok := err.(MultiError); ok {

openapi3/schema_issue940_test.go

@@ -0,0 +1,72 @@
+package openapi3
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOneOfErrorPreserved(t *testing.T) {
+
+	SchemaErrorDetailsDisabled = true
+	defer func() { SchemaErrorDetailsDisabled = false }()
+
+	// language=json
+	raw := `
+{
+	"foo": [ "bar" ]
+}
+`
+
+	// language=json
+	schema := `
+{
+	"type": "object",
+	"properties": {
+		"foo": {
+			"oneOf": [
+				{
+					"type": "number"
+				},
+					{
+					"type": "string"
+				}
+			]
+		}
+	}
+}
+`
+
+	s := NewSchema()
+	err := s.UnmarshalJSON([]byte(schema))
+	require.NoError(t, err)
+	err = s.Validate(context.Background())
+	require.NoError(t, err)
+
+	obj := make(map[string]interface{})
+	err = json.Unmarshal([]byte(raw), &obj)
+	require.NoError(t, err)
+
+	err = s.VisitJSON(obj, MultiErrors())
+	require.Error(t, err)
+
+	var multiError MultiError
+	ok := errors.As(err, &multiError)
+	require.True(t, ok)
+	var schemaErr *SchemaError
+	ok = errors.As(multiError[0], &schemaErr)
+	require.True(t, ok)
+
+	require.Equal(t, "oneOf", schemaErr.SchemaField)
+	require.Equal(t, `value doesn't match any schema from "oneOf"`, schemaErr.Reason)
+	require.Equal(t, `Error at "/foo": doesn't match schema due to: value must be a number Or value must be a string`, schemaErr.Error())
+
+	var me multiErrorForOneOf
+	ok = errors.As(err, &me)
+	require.True(t, ok)
+	require.Equal(t, `Error at "/foo": value must be a number`, me[0].Error())
+	require.Equal(t, `Error at "/foo": value must be a string`, me[1].Error())
+}