Fix false-positive omitempty detection in JSON struct tags

Introduce a hasOmitemptyTag helper that treats "omitempty" as a
comma-delimited option rather than an arbitrary substring.

Signed-off-by: Arthur Diniz <arthurbd@debian.org>

Author: arthurbdiniz

pkg/generators/openapi.go

@@ -100,7 +100,7 @@ func isOptional(m *types.Member) (bool, error) {
 
 	// If neither +optional nor +required is present in the comments,
 	// infer optional from the json tags.
-	return strings.Contains(reflect.StructTag(m.Tags).Get("json"), "omitempty"), nil
+	return hasOmitemptyTag(m), nil
 }
 
 func apiTypeFilterFunc(c *generator.Context, t *types.Type) bool {
@@ -222,6 +222,11 @@ func getReferableName(m *types.Member) string {
 	}
 }
 
+func hasOmitemptyTag(m *types.Member) bool {
+	jsonTag, _ := reflect.StructTag(m.Tags).Lookup("json")
+	return strings.HasSuffix(jsonTag, ",omitempty") || strings.Contains(jsonTag, ",omitempty,")
+}
+
 func shouldInlineMembers(m *types.Member) bool {
 	jsonTag, jsonTagExists := reflect.StructTag(m.Tags).Lookup("json")
 	return m.Embedded && jsonTagExists && (jsonTag == "" || strings.HasPrefix(jsonTag, ","))
@@ -985,7 +990,7 @@ func structZeroDefault(t *types.Type) (interface{}, error) {
 			continue
 		}
 		// Include zero value for this required field
-		memberOmitEmpty := strings.Contains(reflect.StructTag(m.Tags).Get("json"), "omitempty")
+		memberOmitEmpty := hasOmitemptyTag(&m)
 		zero, err := mustEnforceDefault(m.Type, memberOmitEmpty)
 		if err != nil {
 			return nil, err
@@ -1086,7 +1091,7 @@ func (g openAPITypeWriter) generateProperty(m *types.Member, parent *types.Type)
 		g.Do("},\n},\n", nil)
 		return nil
 	}
-	omitEmpty := strings.Contains(reflect.StructTag(m.Tags).Get("json"), "omitempty")
+	omitEmpty := hasOmitemptyTag(m)
 	if err := g.generateDefault(m.CommentLines, m.Type, omitEmpty, parent); err != nil {
 		return fmt.Errorf("failed to generate default in %v: %v: %v", parent, m.Name, err)
 	}

pkg/generators/openapi_test.go

@@ -3363,3 +3363,60 @@ func TestShouldInlineMembers(t *testing.T) {
 		})
 	}
 }
+
+func TestHasOmitemptyTag(t *testing.T) {
+	tests := []struct {
+		name     string
+		member   types.Member
+		expected bool
+	}{
+		{
+			name:     "standard omitempty",
+			member:   types.Member{Tags: `json:"foo,omitempty"`},
+			expected: true,
+		},
+		{
+			name:     "omitempty with no name",
+			member:   types.Member{Tags: `json:",omitempty"`},
+			expected: true,
+		},
+		{
+			name:     "omitempty in the middle of options",
+			member:   types.Member{Tags: `json:"foo,omitempty,string"`},
+			expected: true,
+		},
+		{
+			name:     "no omitempty",
+			member:   types.Member{Tags: `json:"foo"`},
+			expected: false,
+		},
+		{
+			name:     "no json tag",
+			member:   types.Member{Tags: ``},
+			expected: false,
+		},
+		{
+			name:     "field name contains omitempty - should not match",
+			member:   types.Member{Tags: `json:"omitemptyTest"`},
+			expected: false,
+		},
+		{
+			name:     "field name ends with omitempty - should not match",
+			member:   types.Member{Tags: `json:"fooOmitempty"`},
+			expected: false,
+		},
+		{
+			name:     "field name is omitempty with no options - should not match",
+			member:   types.Member{Tags: `json:"omitempty"`},
+			expected: false,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := hasOmitemptyTag(&tc.member); got != tc.expected {
+				t.Errorf("hasOmitemptyTag(%+v) = %v, want %v", tc.member, got, tc.expected)
+			}
+		})
+	}
+}