fix: json marshaling of 'contains' schema

Author: RichardKnop

keywords_array.go

@@ -273,13 +273,31 @@ func (c Contains) JSONChildren() (res map[string]JSONPather) {
 	return Schema(c).JSONChildren()
 }
 
+// MarshalJSON implements the json.Marshaler interface for Schema
+func (c *Contains) MarshalJSON() ([]byte, error) {
+	switch c.schemaType {
+	case schemaTypeFalse:
+		return []byte("false"), nil
+	case schemaTypeTrue:
+		return []byte("true"), nil
+	default:
+		obj := map[string]interface{}{}
+
+		for k, v := range c.keywords {
+			obj[k] = v
+		}
+		return json.Marshal(obj)
+	}
+}
+
 // UnmarshalJSON implements the json.Unmarshaler interface for Contains
 func (c *Contains) UnmarshalJSON(data []byte) error {
 	var sch Schema
 	if err := json.Unmarshal(data, &sch); err != nil {
 		return err
 	}
 	*c = Contains(sch)
+
 	return nil
 }
 

schema_test.go

@@ -617,6 +617,7 @@ func TestJSONCoding(t *testing.T) {
 		"testdata/coding/numeric.json",
 		"testdata/coding/objects.json",
 		"testdata/coding/strings.json",
+		"testdata/coding/contains.json",
 	}
 
 	for i, c := range cases {

testdata/coding/contains.json

@@ -0,0 +1,6 @@
+{
+  "contains": {
+    "const": "foobar"
+  },
+  "type": "array"
+}