Fix openapi3 validation: path param must be required

openapi3/loader_test.go

@@ -412,6 +412,7 @@ paths:
       parameters:
         - name: id,
           in: path
+          required: true
           schema:
             type: string
       responses:

openapi3/parameter.go

@@ -252,6 +252,10 @@ func (value *Parameter) Validate(ctx context.Context) error {
 		return fmt.Errorf("parameter can't have 'in' value %q", value.In)
 	}
 
+	if in == ParameterInPath && !value.Required {
+		return fmt.Errorf("path parameter %q must be required", value.Name)
+	}
+
 	// Validate a parameter's serialization method.
 	sm, err := value.SerializationMethod()
 	if err != nil {

openapi3filter/req_resp_decoder_test.go

@@ -908,6 +908,7 @@ func TestDecodeParameter(t *testing.T) {
 					path := "/test"
 					if tc.path != "" {
 						path += "/{" + tc.param.Name + "}"
+						tc.param.Required = true
 					}
 
 					info := &openapi3.Info{

openapi3filter/validation_test.go

@@ -62,9 +62,10 @@ func TestFilter(t *testing.T) {
 					Parameters: openapi3.Parameters{
 						{
 							Value: &openapi3.Parameter{
-								In:     "path",
-								Name:   "pathArg",
-								Schema: openapi3.NewStringSchema().WithMaxLength(2).NewRef(),
+								In:       "path",
+								Name:     "pathArg",
+								Schema:   openapi3.NewStringSchema().WithMaxLength(2).NewRef(),
+								Required: true,
 							},
 						},
 						{