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operations: add RemoveExisting to safely remove an existing file
This renames the file first and if the operation is successful then it deletes the renamed file.
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parent
3e14ba54b8
commit
2bafbf3c04
@ -1188,6 +1188,57 @@ func Delete(ctx context.Context, f fs.Fs) error {
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return err
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}
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// RemoveExisting removes an existing file in a safe way so that it
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// can be restored if the operation fails.
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//
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// This first detects if there is an existing file and renames it to a
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// temporary name if there is.
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//
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// The returned cleanup function should be called on a defer statement
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// with a pointer to the error returned. It will revert the changes if
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// there is an error or delete the existing file if not.
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func RemoveExisting(ctx context.Context, f fs.Fs, remote string, operation string) (cleanup func(*error), err error) {
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existingObj, err := f.NewObject(ctx, remote)
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if err != nil {
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return func(*error) {}, nil
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}
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doMove := f.Features().Move
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if doMove == nil {
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return nil, fmt.Errorf("%s: destination file exists already and can't rename", operation)
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}
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// Avoid making the leaf name longer if it's already lengthy to avoid
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// trouble with file name length limits.
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suffix := "." + random.String(8)
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var remoteSaved string
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if len(path.Base(remote)) > 100 {
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remoteSaved = TruncateString(remote, len(remote)-len(suffix)) + suffix
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} else {
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remoteSaved = remote + suffix
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}
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fs.Debugf(existingObj, "%s: renaming existing object to %q before starting", operation, remoteSaved)
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existingObj, err = doMove(ctx, existingObj, remoteSaved)
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if err != nil {
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return nil, fmt.Errorf("%s: failed to rename existing file: %w", operation, err)
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}
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return func(perr *error) {
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if *perr == nil {
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fs.Debugf(existingObj, "%s: removing renamed existing file after operation", operation)
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err := existingObj.Remove(ctx)
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if err != nil {
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*perr = fmt.Errorf("%s: failed to remove renamed existing file: %w", operation, err)
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}
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} else {
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fs.Debugf(existingObj, "%s: renaming existing back after failed operation", operation)
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_, renameErr := doMove(ctx, existingObj, remote)
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if renameErr != nil {
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fs.Errorf(existingObj, "%s: failed to restore existing file after failed operation: %v", operation, renameErr)
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}
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}
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}, nil
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}
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// listToChan will transfer all objects in the listing to the output
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//
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// If an error occurs, the error will be logged, and it will close the
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@ -1884,3 +1884,76 @@ func TestDirsEqual(t *testing.T) {
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equal = operations.DirsEqual(ctx, src, dst, opt)
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assert.True(t, equal)
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}
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func TestRemoveExisting(t *testing.T) {
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ctx := context.Background()
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r := fstest.NewRun(t)
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if r.Fremote.Features().Move == nil {
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t.Skip("Skipping as remote can't Move")
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}
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file1 := r.WriteObject(ctx, "sub dir/test remove existing", "hello world", t1)
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file2 := r.WriteObject(ctx, "sub dir/test remove existing with long name 1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890", "hello long name world", t1)
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r.CheckRemoteItems(t, file1, file2)
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var returnedError error
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// Check not found first
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cleanup, err := operations.RemoveExisting(ctx, r.Fremote, "not found", "TEST")
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assert.Equal(t, err, nil)
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r.CheckRemoteItems(t, file1, file2)
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cleanup(&returnedError)
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r.CheckRemoteItems(t, file1, file2)
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// Remove file1
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cleanup, err = operations.RemoveExisting(ctx, r.Fremote, file1.Path, "TEST")
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assert.Equal(t, err, nil)
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//r.CheckRemoteItems(t, file1, file2)
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// Check file1 with temporary name exists
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var buf bytes.Buffer
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err = operations.List(ctx, r.Fremote, &buf)
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require.NoError(t, err)
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res := buf.String()
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assert.NotContains(t, res, " 11 "+file1.Path+"\n")
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assert.Contains(t, res, " 11 "+file1.Path+".")
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assert.Contains(t, res, " 21 "+file2.Path+"\n")
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cleanup(&returnedError)
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r.CheckRemoteItems(t, file2)
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// Remove file2 with an error
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cleanup, err = operations.RemoveExisting(ctx, r.Fremote, file2.Path, "TEST")
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assert.Equal(t, err, nil)
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// Check file2 with truncated temporary name exists
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buf.Reset()
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err = operations.List(ctx, r.Fremote, &buf)
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require.NoError(t, err)
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res = buf.String()
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assert.NotContains(t, res, " 21 "+file2.Path+"\n")
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assert.NotContains(t, res, " 21 "+file2.Path+".")
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assert.Contains(t, res, " 21 "+file2.Path[:100])
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returnedError = errors.New("BOOM")
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cleanup(&returnedError)
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r.CheckRemoteItems(t, file2)
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// Remove file2
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cleanup, err = operations.RemoveExisting(ctx, r.Fremote, file2.Path, "TEST")
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assert.Equal(t, err, nil)
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// Check file2 with truncated temporary name exists
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buf.Reset()
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err = operations.List(ctx, r.Fremote, &buf)
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require.NoError(t, err)
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res = buf.String()
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assert.NotContains(t, res, " 21 "+file2.Path+"\n")
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assert.NotContains(t, res, " 21 "+file2.Path+".")
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assert.Contains(t, res, " 21 "+file2.Path[:100])
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returnedError = nil
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cleanup(&returnedError)
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r.CheckRemoteItems(t)
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}
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