New coll.Merge function

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

2 files changed, 45 insertions, 0 deletions

diff --git a/coll/coll.go b/coll/coll.go
index a9331055..40d2e9d5 100644
--- a/coll/coll.go
+++ b/coll/coll.go
@@ -5,6 +5,8 @@ import (
 	"reflect"
 	"sort"
 
+	"github.com/imdario/mergo"
+
 	"github.com/hairyhenderson/gomplate/conv"
 	"github.com/pkg/errors"
 )
@@ -162,3 +164,15 @@ func Reverse(list interface{}) ([]interface{}, error) {
 	}
 	return l, nil
 }
+
+// Merge source maps (srcs) into dst. Precedence is in left-to-right order, with
+// the left-most values taking precedence over the right-most.
+func Merge(dst map[string]interface{}, srcs ...map[string]interface{}) (map[string]interface{}, error) {
+	for _, src := range srcs {
+		err := mergo.Merge(&dst, src)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return dst, nil
+}
diff --git a/coll/coll_test.go b/coll/coll_test.go
index fff2b02f..db6d4d51 100644
--- a/coll/coll_test.go
+++ b/coll/coll_test.go
@@ -197,3 +197,34 @@ func TestReverse(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, []interface{}{4, 3, 2, 1}, out)
 }
+
+func TestMerge(t *testing.T) {
+	dst := map[string]interface{}{}
+	src := map[string]interface{}{}
+	expected := map[string]interface{}{}
+
+	out, err := Merge(dst, src)
+	assert.NoError(t, err)
+	assert.EqualValues(t, expected, out)
+
+	dst = map[string]interface{}{"a": 4, "c": 5}
+	src = map[string]interface{}{"a": 1, "b": 2, "c": 3}
+	expected = map[string]interface{}{
+		"a": dst["a"], "b": src["b"], "c": dst["c"],
+	}
+
+	out, err = Merge(dst, src)
+	assert.NoError(t, err)
+	assert.EqualValues(t, expected, out)
+
+	dst = map[string]interface{}{"a": 4, "c": 5}
+	src = map[string]interface{}{"a": 1, "b": 2, "c": 3}
+	src2 := map[string]interface{}{"a": 1, "b": 2, "c": 3, "d": 4}
+	expected = map[string]interface{}{
+		"a": dst["a"], "b": src["b"], "c": dst["c"], "d": src2["d"],
+	}
+
+	out, err = Merge(dst, src, src2)
+	assert.NoError(t, err)
+	assert.EqualValues(t, expected, out)
+}