add merge function to dict

dict.go

@@ -1,5 +1,7 @@
 package sprig
 
+import "github.com/imdario/mergo"
+
 func set(d map[string]interface{}, key string, value interface{}) map[string]interface{} {
 	d[key] = value
 	return d
@@ -72,3 +74,11 @@ func dict(v ...interface{}) map[string]interface{} {
 	}
 	return dict
 }
+
+func merge(dst map[string]interface{}, src map[string]interface{}) interface{} {
+	if err := mergo.Merge(&dst, src); err != nil {
+		// Swallow errors inside of a template.
+		return ""
+	}
+	return dst
+}

dict_test.go

@@ -135,3 +135,40 @@ func TestCompact(t *testing.T) {
 		assert.NoError(t, runt(tpl, expect))
 	}
 }
+
+func TestMerge(t *testing.T) {
+	dict := map[string]interface{}{
+		"src": map[string]interface{}{
+			"a": 1,
+			"b": 2,
+			"d": map[string]interface{}{
+				"e": "four",
+			},
+			"g": []int{6, 7},
+		},
+		"dst": map[string]interface{}{
+			"a": "one",
+			"c": 3,
+			"d": map[string]interface{}{
+				"f": 5,
+			},
+			"g": []int{8, 9},
+		},
+	}
+	tpl := `{{merge .dst .src}}`
+	_, err := runRaw(tpl, dict)
+	if err != nil {
+		t.Error(err)
+	}
+	expected := map[string]interface{}{
+		"a": "one", // key overridden
+		"b": 2,     // merged from src
+		"c": 3,     // merged from dst
+		"d": map[string]interface{}{ // deep merge
+			"e": "four",
+			"f": 5,
+		},
+		"g": []int{8, 9}, // overridden - arrays are not merged
+	}
+	assert.Equal(t, expected, dict["dst"])
+}

functions.go

@@ -227,6 +227,7 @@ var genericMap = map[string]interface{}{
 	"keys":   keys,
 	"pick":   pick,
 	"omit":   omit,
+	"merge":  merge,
 
 	"append": push, "push": push,
 	"prepend": prepend,

glide.yaml

@@ -10,3 +10,5 @@ import:
 - package: github.com/Masterminds/semver
   version: v1.2.2
 - package: github.com/stretchr/testify
+- package: github.com/imdario/mergo
+  version: ~0.2.2