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Some time ago, we distributed a toolbox to our users via the MATLAB App Packager, to make it easier to provide future updates, without users having to handle search paths. Now, we wish to distribute an updated version. Usually, re-packaging the toolbox should make a new .mlappinstall file, which asks the user to upgrade. Instead, MATLAB now considers the new version of the app as a unique new app, and installs it again rather than upgrading. Thus, the user will then have the app twice in the Apps pane, one in an outdated version, and one in the new version.

We have been unable to find an explanation for this in the MATLAB documentation nor online. When we install the updated app (so that both versions are present in the Apps pane), further changing it will upgrade it as expected, so unfortunately, we cannot provide a minimal working example, as we cannot reproduce the issue.

The question is this: How does MATLAB establish app uniqueness? The app name and author fields are identical to the original values, and the version number is incremented, so why might MATLAB not recognize that the app is already installed?

ktolbol
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When you had that discontinuity, were you re-packaging using the original .prj file by clicking on it in the file browser in Matlab, or did you run "Package App" again and fill in the same properties?

I think the thing that determines the unique identity of the app is a GUID that is generated behind the scenes by the "Package App" wizard. If you open an existing .prj in the Matlab GUI, it re-uses that GUID. If you run "Package App" again you'll get a fresh GUID regardless of what you put in for the various developer-visible app properties.

You can dig around in the .prj and .mlappinstall files to see this yourself. (I couldn't find it documented anywhere either; I just poked around the files and did some trial and error.) The .prj is just XML, and the .mlappinstall file is a zip file with an "Open Packaging Convention" layout. In the .prj, there's a param.guid element containing the GUID. In the .mlappinstall, its in metadata/appProperties.xml in a GUID element.

If you end up with the same problem again, make sure to re-package using the existing .prj file. Or if you don't have it, once you create your new .prj file, dig the old GUID out of the metadata/appProperties.xml from the old .mlappinstall file and copy it in to your new .prj file and I think it'll behave as the "same" app. This will even let you change the name and contact info for your app, and it'll still install on top of older versions.

Andrew Janke
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