Make MemMapFs implement Lstater

go.mod

@@ -2,6 +2,7 @@ module github.com/spf13/afero
 
 require (
 	github.com/pkg/sftp v1.10.1
+	github.com/stretchr/testify v1.4.0
 	golang.org/x/crypto v0.0.0-20190820162420-60c769a6c586
 	golang.org/x/text v0.3.3
 )

memmap.go

@@ -317,6 +317,11 @@ func (m *MemMapFs) Rename(oldname, newname string) error {
 	return nil
 }
 
+func (m *MemMapFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {
+	fileInfo, err := m.Stat(name)
+	return fileInfo, false, err
+}
+
 func (m *MemMapFs) Stat(name string) (os.FileInfo, error) {
 	f, err := m.Open(name)
 	if err != nil {

memmap_test.go

@@ -8,6 +8,9 @@ import (
 	"runtime"
 	"testing"
 	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestNormalizePath(t *testing.T) {
@@ -650,3 +653,23 @@ func TestMemFsOpenFileModeIllegal(t *testing.T) {
 		t.Fatalf("should not be able to use OpenFile to set illegal mode: %s", info.Mode().String())
 	}
 }
+
+// LstatIfPossible should always return false, since MemMapFs does not
+// support symlinks.
+func TestMemFsLstatIfPossible(t *testing.T) {
+	t.Parallel()
+
+	fs := NewMemMapFs()
+
+	// We assert that fs implements Lstater
+	fsAsserted, ok := fs.(Lstater)
+	require.True(t, ok, "The filesytem does not implement Lstater")
+
+	file, err := fs.OpenFile("/a.txt", os.O_CREATE, 0o644)
+	require.NoError(t, err)
+	defer file.Close()
+
+	_, lstatCalled, err := fsAsserted.LstatIfPossible("/a.txt")
+	assert.NoError(t, err)
+	assert.False(t, lstatCalled)
+}