feat: add Mkdir

dir.go

@@ -217,6 +217,55 @@ func (d *dir) MkdirAll(path string, perm fs.FileMode) error {
 	return d.dirs[parts[0]].MkdirAll(strings.Join(parts[1:], separator), perm)
 }
 
+func (d *dir) Mkdir(path string, perm fs.FileMode) error {
+	parts := strings.Split(path, separator)
+
+	if path == "" {
+		return fs.ErrExist
+	}
+
+	d.RLock()
+	_, fOk := d.files[parts[0]]
+	_, dOk := d.dirs[parts[0]]
+	d.RUnlock()
+	if fOk {
+		return fs.ErrExist
+	}
+	if !dOk && len(parts) > 1 {
+		return fs.ErrNotExist
+	}
+
+	if len(parts) == 1 {
+		d.Lock()
+		if perm&fs.ModeDir == 0 {
+			perm |= fs.ModeDir
+		}
+		_, ok := d.dirs[parts[0]]
+		if !ok {
+			d.dirs[parts[0]] = &dir{
+				info: fileinfo{
+					name:     parts[0],
+					size:     0x100,
+					modified: time.Now(),
+					mode:     perm,
+				},
+				dirs:  map[string]*dir{},
+				files: map[string]*file{},
+			}
+		}
+		d.Unlock()
+		if ok {
+			return fs.ErrExist
+		}
+
+		return nil
+	}
+
+	d.RLock()
+	defer d.RUnlock()
+	return d.dirs[parts[0]].Mkdir(strings.Join(parts[1:], separator), perm)
+}
+
 func (d *dir) WriteFile(path string, data []byte, perm fs.FileMode) error {
 	parts := strings.Split(path, separator)
 

fs.go

@@ -89,6 +89,13 @@ func (m *FS) MkdirAll(path string, perm fs.FileMode) error {
 	return m.dir.MkdirAll(cleanse(path), perm)
 }
 
+// Mkdir create a directory named path.
+// Parent attributes are preserved.
+// If path is already exists, returns an error.
+func (m *FS) Mkdir(path string, perm fs.FileMode) error {
+	return m.dir.Mkdir(cleanse(path), perm)
+}
+
 // ReadFile reads the named file and returns its contents.
 // A successful call returns a nil error, not io.EOF.
 // (Because ReadFile reads the whole file, the expected EOF

fs_test.go

@@ -525,6 +525,84 @@ func Test_MkdirAllRoot(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func Test_Mkdir(t *testing.T) {
+	memfs := New()
+	rootStat, err := memfs.Stat("/")
+	require.NoError(t, err)
+
+	rootMode := rootStat.Mode()
+	rootModTime := rootStat.ModTime()
+
+	t.Run("create directory on root", func(t *testing.T) {
+
+		err = memfs.Mkdir("/dir", 0o444)
+		assert.NoError(t, err)
+
+		stat, err := memfs.Stat("/dir")
+		assert.NoError(t, err)
+		assert.Equal(t, 0o444|fs.ModeDir, stat.Mode())
+
+		rootStat, err := memfs.Stat("/")
+		assert.NoError(t, err)
+		assert.Equal(t, rootMode, rootStat.Mode())
+		assert.Equal(t, rootModTime, rootStat.ModTime())
+	})
+
+	t.Run("create directory on sub directory", func(t *testing.T) {
+		err := memfs.Mkdir("/sub", 0o444)
+		assert.NoError(t, err)
+
+		subStat, err := memfs.Stat("/sub")
+		require.NoError(t, err)
+		subMode := subStat.Mode()
+		subModTime := subStat.ModTime()
+
+		err = memfs.Mkdir("/sub/dir", 0o666)
+		assert.NoError(t, err)
+
+		stat, err := memfs.Stat("/sub/dir")
+		assert.NoError(t, err)
+		assert.Equal(t, 0o666|fs.ModeDir, stat.Mode())
+
+		subStat, err = memfs.Stat("/sub")
+		assert.NoError(t, err)
+		assert.Equal(t, subMode, subStat.Mode())
+		assert.Equal(t, subModTime, subStat.ModTime())
+
+		rootStat, err := memfs.Stat("/")
+		assert.NoError(t, err)
+		assert.Equal(t, rootMode, rootStat.Mode())
+		assert.Equal(t, rootModTime, rootStat.ModTime())
+	})
+
+	t.Run("file already exists", func(t *testing.T) {
+		err := memfs.WriteFile("/file", []byte{}, 0o777)
+		assert.NoError(t, err)
+
+		err = memfs.Mkdir("/file", 0o644)
+		assert.Error(t, err)
+
+		err = memfs.Mkdir("/file/dir", 0o644)
+		assert.Error(t, err)
+	})
+
+	t.Run("directory already exists", func(t *testing.T) {
+		err := memfs.Mkdir("/", 0o644)
+		assert.Error(t, err)
+
+		err = memfs.Mkdir("/exists", 0o444)
+		assert.NoError(t, err)
+
+		err = memfs.Mkdir("/exists", 0o444)
+		assert.Error(t, err)
+	})
+
+	t.Run("parent not exists", func(t *testing.T) {
+		err := memfs.Mkdir("/not_exists/dir", 0o644)
+		assert.Error(t, err)
+	})
+}
+
 type entry struct {
 	path string
 	info fs.DirEntry