implement RFC7386 JSON Merge Patch

pkg/util/merge/merge.go

@@ -0,0 +1,57 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package merge
+
+import (
+	"encoding/json"
+)
+
+// MergeJSON merges JSON according to RFC7386
+// (see https://tools.ietf.org/html/rfc7386)
+func MergeJSON(dst, src []byte) ([]byte, error) {
+	var target interface{}
+	if err := json.Unmarshal(dst, &target); err != nil {
+		return nil, err
+	}
+	var patch interface{}
+	if err := json.Unmarshal(src, &patch); err != nil {
+		return nil, err
+	}
+	return json.Marshal(MergePatch(target, patch))
+}
+
+// MergePatch is an implementation of MergePatch described in RFC7386 that operates on
+// json marshalled into empty interface{} by encoding/json.Unmarshal()
+// (see https://tools.ietf.org/html/rfc7386#section-2)
+func MergePatch(target, patch interface{}) interface{} {
+	if patchObject, isPatchObject := patch.(map[string]interface{}); isPatchObject {
+		targetObject := make(map[string]interface{})
+		if m, isTargetObject := target.(map[string]interface{}); isTargetObject {
+			targetObject = m
+		}
+		for name, value := range patchObject {
+			if _, found := targetObject[name]; value == nil && found {
+				delete(targetObject, name)
+			} else {
+				targetObject[name] = MergePatch(targetObject[name], value)
+			}
+		}
+		return targetObject
+	} else {
+		return patch
+	}
+}

pkg/util/merge/merge_test.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package merge
+
+import (
+	"testing"
+)
+
+func TestMergeJSON(t *testing.T) {
+	tests := []struct {
+		target   string
+		patch    string
+		expected string
+	}{
+		{target: `{}`, patch: `{}`, expected: `{}`},
+		{target: `{"a":"b","c":{"d":"e","f":"g"}}`, patch: `{}`, expected: `{"a":"b","c":{"d":"e","f":"g"}}`},
+		//update
+		{target: `{"a":"b","c":"d"}`, patch: `{"a":"z"}`, expected: `{"a":"z","c":"d"}`},
+		//remove key
+		{target: `{"f":"g"}`, patch: `{"f":null}`, expected: `{}`},
+		//inner update
+		{target: `{"c":{"d":"e","f":"g"}}`, patch: `{"c":{"f":"z"}}`, expected: `{"c":{"d":"e","f":"z"}}`},
+		//inner remove
+		{target: `{"c":{"d":"e","f":"g"}}`, patch: `{"c":{"f":null}}`, expected: `{"c":{"d":"e"}}`},
+		//complex update and remove
+		{target: `{"a":"b","c":{"d":"e","f":"g"}}`, patch: `{"a":"z","c":{"f":null}}`, expected: `{"a":"z","c":{"d":"e"}}`},
+		// test cases from https://tools.ietf.org/html/rfc7386#appendix-A slightly adapted to correspond to go's
+		// encoding/json conventions
+		{target: `{"a":"b"}`, patch: `{"a":"c"}`, expected: `{"a":"c"}`},
+		{target: `{"a":"b"}`, patch: `{"b":"c"}`, expected: `{"a":"b","b":"c"}`},
+		{target: `{"a":"b"}`, patch: `{"a":null}`, expected: `{}`},
+		{target: `{"a":"b","b":"c"}`, patch: `{"a":null}`, expected: `{"b":"c"}`},
+		{target: `{"a":["b"]}`, patch: `{"a":"c"}`, expected: `{"a":"c"}`},
+		{target: `{"a":"c"}`, patch: `{"a":["b"]}`, expected: `{"a":["b"]}`},
+		{target: `{"a":{"b": "c"}}`, patch: `{"a": {"b": "d","c": null}}`, expected: `{"a":{"b":"d","c":null}}`},
+		{target: `{"a":[{"b":"c"}]}`, patch: `{"a":[1]}`, expected: `{"a":[1]}`},
+		{target: `["a","b"]`, patch: `["c","d"]`, expected: `["c","d"]`},
+		{target: `{"a":"b"}`, patch: `["c"]`, expected: `["c"]`},
+		{target: `{"a":"foo"}`, patch: `null`, expected: `null`},
+		{target: `{"a":"foo"}`, patch: `"bar"`, expected: `"bar"`},
+		{target: `{"e":null}`, patch: `{"a":1}`, expected: `{"a":1,"e":null}`},
+		{target: `[1,2]`, patch: `{"a":"b","c":null}`, expected: `{"a":"b","c":null}`},
+		{target: `{}`, patch: `{"a":{"bb":{"ccc":null}}}`, expected: `{"a":{"bb":{"ccc":null}}}`},
+	}
+	for i, test := range tests {
+		out, err := MergeJSON([]byte(test.target), []byte(test.patch))
+		if err != nil {
+			t.Errorf("case %v, unexpected error: %v", i, err)
+		}
+		if string(out) != test.expected {
+			t.Errorf("case %v, expected:\n%v\nsaw:\n%v\n", i, test.expected, string(out))
+		}
+	}
+}