From ac4ea73cdbf6a25c169dbdce5e46defd56553600 Mon Sep 17 00:00:00 2001
From: Grégoire Duchêne <gduchene@awhk.org>
Date: Sun, 11 Dec 2022 14:15:03 +0000
Subject: Add MapKeys

---
 util.go      | 14 ++++++++++++++
 util_test.go | 11 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/util.go b/util.go
index ec2a3dd..47a785a 100644
--- a/util.go
+++ b/util.go
@@ -3,6 +3,20 @@
 
 package core
 
+// MapKeys returns a slice containing all the keys of the map supplied.
+// It basically is https://pkg.go.dev/golang.org/x/exp/maps#Keys, but
+// that package is still unstable.
+func MapKeys[T ~map[K]V, K comparable, V any](m T) []K {
+	if len(m) == 0 {
+		return nil
+	}
+	ret := make([]K, 0, len(m))
+	for k := range m {
+		ret = append(ret, k)
+	}
+	return ret
+}
+
 // Must panics if err is not nil. It returns val otherwise.
 func Must[T any](val T, err error) T {
 	if err != nil {
diff --git a/util_test.go b/util_test.go
index a9b297e..f8731e5 100644
--- a/util_test.go
+++ b/util_test.go
@@ -5,6 +5,7 @@ package core_test
 
 import (
 	"errors"
+	"sort"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -13,6 +14,16 @@ import (
 	"go.awhk.org/core"
 )
 
+func TestMapKeys(s *testing.T) {
+	t := core.T{T: s}
+
+	t.AssertEqual(([]string)(nil), core.MapKeys[map[string]int](nil))
+	t.AssertEqual(([]string)(nil), core.MapKeys(map[string]int{}))
+	keys := core.MapKeys(map[string]int{"foo": 1, "bar": 2})
+	sort.Strings(keys)
+	t.AssertEqual([]string{"bar", "foo"}, keys)
+}
+
 func TestMust(s *testing.T) {
 	t := core.T{T: s, Options: []cmp.Option{cmpopts.EquateErrors()}}
 
-- 
cgit v1.2.3-70-g09d2