MemMapFS doesn't properly rename directories

[kklin]

When I rename a directory with MemMapFS, the files within it don't get moved. I think the files within should also move to the new directory name (as in the behavior of mv <old_dir> <new_dir>), but maybe I'm misunderstanding how Rename works.

I've written a unit test that shows the error:

// TestRenameDirectory creates a directory with a file, and attempts to rename
// the directory. The child file should also be within the renamed directory.
func TestRenameDirectory(t *testing.T) {
        fs := NewMemMapFs()

        srcDir := "/src-dir"
        dstDir := "/dst-dir"
        filename := "file"
        fileInSrcDir := filepath.Join(srcDir, filename)
        fileInDstDir := filepath.Join(dstDir, filename)

        if err := fs.Mkdir(srcDir, 755); err != nil {
                t.Fatalf("Mkdir failed unexpectedly: %s", err)
        }

        if _, err := fs.Create(fileInSrcDir); err != nil {
                t.Fatalf("Create file failed unexpectedly: %s", err)
        }

        if err := fs.Rename(srcDir, dstDir); err != nil {
                t.Fatalf("Rename failed unexpectedly: %s", err)
        }

        if _, err := fs.Stat(fileInSrcDir); err == nil {
                t.Error("The file should not be in the old directory")
        }

        if _, err := fs.Stat(fileInDstDir); err != nil {
                t.Errorf("The file should be in the new directory: %s", err)
        }
}

--- FAIL: TestRenameDirectory (0.00s)
        memmap_test.go:371: The file should not be in the old directory
        memmap_test.go:375: The file should be in the new directory: open /dst-dir/file: file does not exist

I could help out fixing this, but I'm not sure how to approach it. I took a quick glance at the way the filesystem is represented within MemMapFS, and didn't completely understand it.

Thanks!

[mtaufen]

I also noticed this recently while unit testing something that moves directories with MemMapFS; it would work if I tested with the OS default filesystem, but not with MemMapFS.

[jeanlucmongrain]

Confirm

func TestAferoRename(t *testing.T) {
	fs := afero.NewMemMapFs()
	require.NoError(t, fs.MkdirAll("/d1/d2/d3", 755))
	f, err := fs.OpenFile("/d1/d2/d3/f1", os.O_CREATE|os.O_WRONLY, 0644)
	require.NoError(t, err)
	_, err = f.WriteString("asaagsd")
	require.NoError(t, err)
	require.NoError(t, f.Close())

	files, err := afero.Glob(fs, "/d1/d2/d3/*")
	require.NoError(t, err)
	require.Len(t, files, 1)

	require.NoError(t, fs.Rename("/d1/d2", "/d1/d4"))

	files, err = afero.Glob(fs, "/d1/d2/d3/*")
	require.NoError(t, err)
	require.Len(t, files, 0)

	files, err = afero.Glob(fs, "/d1/d4/*")
	require.NoError(t, err)
	require.Len(t, files, 1)
}

output:

=== RUN   TestAferoRename
--- FAIL: TestAferoRename (0.00s)
        Error Trace:    server_test.go:43
        Error:          "[/d1/d2/d3/f1]" should have 0 item(s), but has 1

[Dreznel]

Hello,

Just wanted to chime in and say that I'm having the same trouble with this. I'm unit testing with MemMapFs and finding that fs.Rename doesn't seem to be doing anything. I might be doing something wrong, but the code seems to work fine when we're using an OS filesystem.

(here's my code, if it helps at all)

func (suite *UtilsTestSuite) TestRollbackUpdatePackages_RestoresWhenNoActiveInstallation() {
	_ = suite.FileSystem.MkdirAll("test-library/__OLD__CatsAndOranges", 0755)
	_, _ = suite.FileSystem.Create("test-library/__OLD__CatsAndOranges/DESCRIPTION")
	f, _ := suite.FileSystem.Open("test-library/__OLD__CatsAndOranges/DESCRIPTION")
	f.WriteString("contents")
	defer f.Close()

	updateAttemptFixture := []UpdateAttempt{
		UpdateAttempt{
			Package:                "CatsAndOranges",
			BackupPackageDirectory: "test-library/__OLD__CatsAndOranges",
			ActivePackageDirectory: "test-library/CatsAndOranges",
			NewVersion:             "2",
			OldVersion:             "1",
		},
	}

        // Should call fs.Rename("test-library/__OLD__CatsAndOranges", "test-library/CatsAndOranges")
	RollbackUpdatePackages(suite.FileSystem, updateAttemptFixture)

        //Line fails
	suite.True(afero.DirExists(suite.FileSystem, "/test-library/CatsAndOranges"))
        //Line fails
	suite.True(afero.Exists(suite.FileSystem, "/test-library/CatsAndOranges/DESCRIPTION"))

         //Both of these succeed
	suite.False(afero.DirExists(suite.FileSystem, "/test-library/__OLD__CatsAndOranges"))
	suite.False(afero.Exists(suite.FileSystem, "/test-library/__OLD__CatsAndOranges/DESCRIPTION"))

}

[maxkaneco]

Please fix this issue. This sorta defeat the whole point of using afero, which allows me to use memfs for testing.

[hanagantig]

Please check my PR with fix. I can't use the library with this bug.

[hanagantig]

Actually this merged PR will not work.

You need to update underlying memdir map as well.
here is a case where you will get a panic:

fs := NewMemMapFs()

err := fs.MkdirAll("src/originDir", 0o777)
if err != nil {
    t.Fatalf("MkDirAll failed: %s", err)
}

f, err := fs.Create("src/originDir/originFile.txt")
if err != nil {
    t.Fatalf("Create failed: %s", err)
}
if err = f.Close(); err != nil {
    t.Fatalf("Close failed: %s", err)
}

err = fs.Rename("src/originDir", "src/updatedDir")
if err != nil {
t.Fatalf("Rename failed: %s", err)
}

err = fs.Rename("src/updatedDir/originFile.txt", "src/updatedDir/updatedFile.txt")
if err != nil {
t.Fatalf("Rename failed: %s", err)
}

@bep please have a look to my PR which I did almost a year ago.