fix: MemMapFs.OpenFile checks parent dir exists before creating file

afero_test.go

@@ -45,6 +45,8 @@ func testDir(fs Fs) string {
 }
 
 func tmpFile(fs Fs) File {
+	// Ensure the temp directory hierarchy exists in the filesystem.
+	fs.MkdirAll(os.TempDir(), 0o700)
 	x, err := TempFile(fs, "", "afero")
 	if err != nil {
 		panic(fmt.Sprint("unable to work with temp file", err))

ioutil_test.go

@@ -16,6 +16,7 @@
 package afero
 
 import (
+	"os"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -33,6 +34,7 @@ func checkSizePath(t *testing.T, path string, size int64) {
 
 func TestReadFile(t *testing.T) {
 	testFS = &MemMapFs{}
+	testFS.MkdirAll(os.TempDir(), 0o700)
 	fsutil := &Afero{Fs: testFS}
 
 	testFS.Create("this_exists.go")
@@ -53,6 +55,7 @@ func TestReadFile(t *testing.T) {
 
 func TestWriteFile(t *testing.T) {
 	testFS = &MemMapFs{}
+	testFS.MkdirAll(os.TempDir(), 0o700)
 	fsutil := &Afero{Fs: testFS}
 	f, err := fsutil.TempFile("", "ioutil-test")
 	if err != nil {
@@ -83,6 +86,7 @@ func TestWriteFile(t *testing.T) {
 
 func TestReadDir(t *testing.T) {
 	testFS = &MemMapFs{}
+	testFS.MkdirAll(os.TempDir(), 0o700)
 	testFS.Mkdir("/i-am-a-dir", 0o777)
 	testFS.Create("/this_exists.go")
 	dirname := "rumpelstilzchen"
@@ -162,7 +166,9 @@ func TestTempFile(t *testing.T) {
 	}
 	for name, tt := range tests {
 		t.Run(name, func(t *testing.T) {
-			file, err := TempFile(NewMemMapFs(), tt.args.dir, tt.args.pattern)
+			fs := NewMemMapFs()
+			fs.MkdirAll(os.TempDir(), 0o700)
+			file, err := TempFile(fs, tt.args.dir, tt.args.pattern)
 			if err != nil {
 				t.Errorf("TempFile() error = %v, none expected", err)
 				return

lstater_test.go

@@ -51,6 +51,7 @@ func TestLstatIfPossible(t *testing.T) {
 	pathFileMem := filepath.Join(memWorkDir, "aferom.txt")
 
 	WriteFile(osFs, filepath.Join(workDir, "afero.txt"), []byte("Hi, Afero!"), 0o777)
+	memFs.MkdirAll(memWorkDir, 0o777)
 	WriteFile(memFs, filepath.Join(pathFileMem), []byte("Hi, Afero!"), 0o777)
 
 	os.Chdir(workDir)

memmap.go

@@ -247,6 +247,15 @@ func (m *MemMapFs) OpenFile(name string, flag int, perm os.FileMode) (File, erro
 		return nil, &os.PathError{Op: "open", Path: name, Err: ErrFileExists}
 	}
 	if os.IsNotExist(err) && (flag&os.O_CREATE > 0) {
+		// Check that the parent directory exists before creating the file,
+		// matching os.OpenFile semantics.
+		parentDir := normalizePath(filepath.Dir(normalizePath(name)))
+		m.mu.RLock()
+		_, parentExists := m.getData()[parentDir]
+		m.mu.RUnlock()
+		if !parentExists {
+			return nil, &os.PathError{Op: "open", Path: name, Err: os.ErrNotExist}
+		}
 		file, err = m.Create(name)
 		chmod = true
 	}

memmap_test.go

@@ -918,3 +918,34 @@ func TestMemMapFsRename(t *testing.T) {
 		}
 	}
 }
+
+func TestOpenFileNonExistentDirectory(t *testing.T) {
+	// Verify that OpenFile with O_CREATE returns an error when the parent
+	// directory does not exist, matching os.OpenFile behavior.
+	// See https://github.com/spf13/afero/issues/270
+	fs := NewMemMapFs()
+
+	err := WriteFile(fs, "/nonexistent/dir/file.txt", []byte("content"), 0o644)
+	if err == nil {
+		t.Fatal("expected error when writing to a non-existent directory, got nil")
+	}
+	if !os.IsNotExist(err) {
+		t.Fatalf("expected os.ErrNotExist, got: %v", err)
+	}
+
+	// Verify it works when the directory is created first.
+	fs.MkdirAll("/existing/dir", 0o755)
+	err = WriteFile(fs, "/existing/dir/file.txt", []byte("content"), 0o644)
+	if err != nil {
+		t.Fatalf("expected no error when writing to an existing directory, got: %v", err)
+	}
+
+	// Verify the written content.
+	data, err := ReadFile(fs, "/existing/dir/file.txt")
+	if err != nil {
+		t.Fatalf("failed to read back written file: %v", err)
+	}
+	if string(data) != "content" {
+		t.Fatalf("expected 'content', got %q", string(data))
+	}
+}

util_test.go

@@ -67,6 +67,7 @@ func TestDirExists(t *testing.T) {
 
 func TestIsDir(t *testing.T) {
 	testFS = new(MemMapFs)
+	testFS.MkdirAll(os.TempDir(), 0o700)
 
 	type test struct {
 		input    string
@@ -90,6 +91,7 @@ func TestIsDir(t *testing.T) {
 
 func TestIsEmpty(t *testing.T) {
 	testFS = new(MemMapFs)
+	testFS.MkdirAll(os.TempDir(), 0o700)
 
 	zeroSizedFile, _ := createZeroSizedFileInTempDir()
 	defer deleteFileInTempDir(zeroSizedFile)