2 files changed, 59 insertions, 5 deletions
diff --git a/pkg/config/merge.go b/pkg/config/merge.go
index 49a7254de..3d8193c02 100644
--- a/pkg/config/merge.go
+++ b/pkg/config/merge.go
@@ -9,7 +9,7 @@ import (
 
 // Unfortunately, if we want to apply a JSON patch to some configuration, we cannot just unmarshal
 // it twice - in that case json.RawMessage objects will be completely replaced, but not merged.
-func MergeJSONData(left, right []byte) ([]byte, error) {
+func MergeJSONs(left, right []byte) ([]byte, error) {
 	vLeft, err := parseFragment(left)
 	if err != nil {
 		return nil, err
@@ -18,8 +18,17 @@ func MergeJSONData(left, right []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	merged := mergeRecursive(vLeft, vRight)
-	return json.Marshal(merged)
+	return json.Marshal(mergeRecursive(vLeft, vRight))
+}
+
+// Recursively apply a patch to a raw JSON data.
+// Patch is supposed to be a map, which possibly nests other map objects.
+func PatchJSON(left []byte, patch map[string]interface{}) ([]byte, error) {
+	vLeft, err := parseFragment(left)
+	if err != nil {
+		return nil, err
+	}
+	return json.Marshal(mergeRecursive(vLeft, patch))
 }
 
 func parseFragment(input []byte) (parsed interface{}, err error) {
diff --git a/pkg/config/merge_test.go b/pkg/config/merge_test.go
index c5a45754e..6785534f1 100644
--- a/pkg/config/merge_test.go
+++ b/pkg/config/merge_test.go
@@ -10,7 +10,7 @@ import (
 	"github.com/google/syzkaller/pkg/config"
 )
 
-func TestMergeJSONData(t *testing.T) {
+func TestMergeJSONs(t *testing.T) {
 	tests := []struct {
 		left   string
 		right  string
@@ -38,7 +38,52 @@ func TestMergeJSONData(t *testing.T) {
 		},
 	}
 	for _, test := range tests {
-		res, err := config.MergeJSONData([]byte(test.left), []byte(test.right))
+		res, err := config.MergeJSONs([]byte(test.left), []byte(test.right))
+		if err != nil {
+			t.Errorf("unexpected error: %s", err)
+		}
+		if !bytes.Equal(res, []byte(test.result)) {
+			t.Errorf("expected %s, got %s", test.result, res)
+		}
+	}
+}
+
+func TestPatchJSON(t *testing.T) {
+	tests := []struct {
+		left   string
+		patch  map[string]interface{}
+		result string
+	}{
+		{
+			`{"a":1,"b":2}`,
+			map[string]interface{}{"b": "string val"},
+			`{"a":1,"b":"string val"}`,
+		},
+		{
+			`{"a":1,"b":2}`,
+			map[string]interface{}{
+				"a": map[string]interface{}{
+					"b": map[string]interface{}{
+						"c": 5,
+					},
+				},
+			},
+			`{"a":{"b":{"c":5}},"b":2}`,
+		},
+		{
+			`{}`,
+			map[string]interface{}{
+				"a": map[string]interface{}{
+					"b": map[string]interface{}{
+						"c": 0,
+					},
+				},
+			},
+			`{"a":{"b":{"c":0}}}`,
+		},
+	}
+	for _, test := range tests {
+		res, err := config.PatchJSON([]byte(test.left), test.patch)
 		if err != nil {
 			t.Errorf("unexpected error: %s", err)
 		}