Support any map type in the keys function

dict.go

@@ -1,6 +1,9 @@
 package sprig
 
 import (
+	"fmt"
+	"reflect"
+
 	"dario.cat/mergo"
 	"github.com/mitchellh/copystructure"
 )
@@ -37,11 +40,15 @@ func pluck(key string, d ...map[string]interface{}) []interface{} {
 	return res
 }
 
-func keys(dicts ...map[string]interface{}) []string {
+func keys(dicts ...interface{}) []string {
 	k := []string{}
 	for _, dict := range dicts {
-		for key := range dict {
-			k = append(k, key)
+		m := reflect.ValueOf(dict)
+		if m.Kind() != reflect.Map {
+			continue
+		}
+		for _, key := range m.MapKeys() {
+			k = append(k, fmt.Sprint(key.Interface()))
 		}
 	}
 	return k

dict_test.go

@@ -82,6 +82,24 @@ func TestKeys(t *testing.T) {
 	}
 }
 
+func TestKeysWithTypedMaps(t *testing.T) {
+	// keys should work with maps whose value type is not interface{} (issue #455).
+	type item struct{ N int }
+	vars := map[string]interface{}{
+		"structMap": map[string]item{"foo": {1}, "bar": {2}},
+		"intMap":    map[string]int{"a": 1, "b": 2},
+	}
+	tests := map[string]string{
+		`{{ keys .structMap | sortAlpha }}`: "[bar foo]",
+		`{{ keys .intMap | sortAlpha }}`:    "[a b]",
+	}
+	for tpl, expect := range tests {
+		if err := runtv(tpl, expect, vars); err != nil {
+			t.Error(err)
+		}
+	}
+}
+
 func TestPick(t *testing.T) {
 	tests := map[string]string{
 		`{{- $d := dict "one" 1 "two" 222222 }}{{ pick $d "two" | len -}}`:               "1",

docs/dicts.md

@@ -184,7 +184,8 @@ deepCopy $source | mergeOverwrite $dest
 ## keys
 
 The `keys` function will return a `list` of all of the keys in one or more `dict`
-types. Since a dictionary is _unordered_, the keys will not be in a predictable order.
+types. Any map type is accepted, not only `dict` (`map[string]interface{}`).
+Since a dictionary is _unordered_, the keys will not be in a predictable order.
 They can be sorted with `sortAlpha`.
 
 ```