[Question] What to say to app dev when "is not a proper AppImage", "too short" ?

[KaKi87]

Hi,

I'm using an app for which appimaged throws this error, but it doesn't explain much, and it doesn't prevent the app from working normally, so if I report it as is to a dev, I'm probably gonna get rejected like "it's the third party launcher's problem, not mine".

So, if it's truly the app's responsibility, then is there additional information supporting this statement that I could add, and if possible, suggestions ?

Actually, what would be even better is if you could write a special fixing documentation that I could link to (and add that link to the notification message).

Thanks

[CalebQ42]

For the too short, that's specifically relating to the zsync update information being malformed. The error text should probably be updated to mention that. not a valid AppImage, that is usually due to the AppImage not containing the "magic" number that denotes that a file is an AppImage, or the file could be corrupted.

[KaKi87]

Hmm, I searched "zsync" in the app's whole repo and found no result. Could it be non-applicable ? The app is Stellarium. Thanks

[CalebQ42]

Specifically it's this block that's causing the error, but it's non critical and doesn't cause the image to not work. I'll check out the AppImage to see why it's saying it's not an AppImage when I get home.

[probonopd]

Thanks to #271, the message should now be more explicit. Please comment here if you think this is still not fully resolved. Thanks!

[KaKi87]

How about a documentation explaining the author how to fix it ? Thanks

[probonopd]

Please refer to https://docs.appimage.org/packaging-guide/optional/updates.html and https://github.com/AppImage/AppImageSpec/blob/master/draft.md#update-information. Thanks!

[KaKi87]

But, the first link says can and the second uses may, so it's optional ?

[probonopd]

Yes, update information is optional (but highly recommended) to have.

[KaKi87]

Then please remove this altogether, as it's not an error.

[probonopd]

Where are you seeing this? For an AppImage that contains no update information at all, or one that contains bad (too short) update information?

[KaKi87]

As I mentioned, the app is Stellarium. Thanks

[probonopd]

The Stellarium AppImage contains the string "None" as update information. The string "None" is not valid update information. Hence, the AppImage is not a valid AppImage.

@probonopd ➜ /workspaces/go-appimage (master) $ objdump -x ./stellarium-24.1-qt5-x86_64.AppImage | grep upd
 27 .upd_info     00000400  0000000000000000  0000000000000000  0002c38f  2**0
@probonopd ➜ /workspaces/go-appimage (master) $ dd if=./stellarium-24.1-qt5-x86_64.AppImage skip=181135 bs=1 count=1024 | xxd
00000000: 4e6f 6e65 0000 0000 0000 0000 0000 0000  None............

If the Stellarium developers would like to produce an AppImage that contains no update information, then they should not put the string "None" there but null bytes (0x00).

[probonopd]

Opened an upstream issue:

• Invalid update information in AppImage Stellarium/stellarium#3726

[KaKi87]

Thanks, I was looking into the origin of this as well and found the same value (you selected one wrong line below the actual one in the qt6 file though).

So, what value should they be using instead ?

They're building the AppImage with appimage-builder as per lines 44 and 88 of this file.

The documentation doesn't really say : https://appimage-builder.readthedocs.io/en/latest/reference/recipe.html#appimage

Thanks

[probonopd]

That would be a question for the appimage-builder team. If I may have a wild guess, just leave away the entire line?

[KaKi87]

Well, actually, have a look at this :

https://github.com/AppImageCrafters/appimage-builder/blob/61c8ddde9ef44b85d7444bbe79d80b44a6a5576d/appimagebuilder/modules/appimage.py#L29

So yes it's optional, but it would still use "none" by default 🤔

And there are many examples using it in there : https://github.com/AppImageCrafters/appimage-builder/tree/61c8ddde9ef44b85d7444bbe79d80b44a6a5576d/recipes

[probonopd]

In any case, then it needs to be fixed there. "None" is not a valid value for update information.

[probonopd]

Hello @KaKi87

Please check the fresh version (development snapshot) of Stellarium as mentioned by @alex-w here:
https://github.com/Stellarium/stellarium-data/releases/tag/weekly-snapshot