Warning: Temporary folder could not be deleted

Every time I save the app source, I get a new directory in the current directory with a name like appDesignerTempData_964888535199

and an error message:

Warning: Temporary folder C:\Users\lent\Dropbox\MATLABappdesigner\BasicSliderPlot\appDesignerTempData_964888535199 could not be deleted.

Please delete manually.

(Bold face is the current folder)

They accumulate.

I tried running as administrator and it doesn't help.

How do I get this temporary file creation to stop?

[Lisa R. Thompson]

Also having this same problem (on both 2020a and 2020b pre-release versions). Also using Dropbox, but could just be coincidence.

[XINWEN YAO]

same here. Running matlab app in dropbox in a windows PC.

And it seems not a problem in Mac + dropbox.

[Tommaso Ferrario]

same problem

[Colin Field]

Same problem, also running Dropbox.

[Adam Danz]

Try removing the directory from the Matlab path using rmpath(__)

Has anyone tried to manually delete the folder as the error message suggests?

As a last resort, if the app is still open and unsaved, backup all of the code into a saved text file (select-all, copy, paste) then close down matlab. When matlab reopens, does the problem persist? If so, try restoredefaultpath.

[Lisa R. Thompson]

Thank you for the advice. On my computer, the problem seems to have resolved recently without user intervention. It had been filling up the folder containing the app with temp files upon every app save. Currently running 2020b release version. Had previously tried restoring the default path in the 2020a and 2020b pre-release versions without any success in changing of temp file problem.

[Laurenz Muessig]

I have the same issue (2020a). I can delete the folders manually, but obviously that's a bit annoying.

[Craig Lent]

Still a problem in 2021a

[Dmitry Kaplan]

Still a problem in R2022a. I believe also that it's the interaction between Dropbox and Matlab, but not simply due to a cloud backup -- more like preparing for a cloud backup... I think... (because I don't see any backup activity on those). See my suggestion below for a change to the serialization code that moves the backup directories to the temp directory, where it truly belongs. I don't feel qualified suggesting it as an answer since the files involved are in a write-only directory and the whole 'temp' vs 'tmp', win/pc/apple/whatever associated issues.

Answer 1

[Cris LaPierre]

I suspect this has to do with you saving to a Dropbox folder. My guess is that Dropbox is doing something with the file when MATLAB tries to delete it (likely actively syncing it to the cloud).

You might be able to confirm this by saving your source to a folder that is not in your Dropbox folder and see if you still get the same warning.

[Dmitry Kaplan]

I think it is the interaction between matlab and dropbox that's the problem. I suspect this will be a problem with many continuous backup systems. Matlab can easily address this by storing the appDesignerTempData where it belongs -- in a "temp" directory, not in pwd(). Or let us pick the location.

Another option may be in fileWriter.m in appdesigner\+appdesigner\+internal\+serialization

         % create a random folder name so no existing folders are affected
            randomNumber = floor(rand*1e12);
            testDirPrefix = 'appDesignerTempData_';
            
            % START NEW:  may want to consider something like
            if ~isempty(getenv('Temp'))
                testDirPrefix = fullfile(getenv('Temp'),testDirPrefix);
            end
            % END NEW
            
            testDir = [testDirPrefix, num2str(randomNumber)];