[TWEAK] Non-Steam Game Prefix Support

[keygenesis]

Target Application

Game: The Elder Scrolls Online (non-Steam game added via Steam)
Compatdata ID: 2658462558

Description

Prefixer can't find Proton prefixes for non-Steam games added through Steam.

The prefix is located at:

~/.local/share/Steam/steamapps/compatdata/2658462558

But running:

prefixer 2658462558 info

gives:

ERROR: The specified Prefix couldn't be found!

Fuzzy name matching doesn't work either (as I expected). Non-Steam entries aren't in Steam's app
metadata, so it just matches to unrelated titles instead.

Expected Behavior

You should be able to target a prefix that lives in compatdata/ even if it's not
tied to a real Steam AppID. This could work via:

• Direct compatdata ID (what I tried above)
• Explicit path as an argument

Actual Behavior

• Only resolves prefixes that exist locally and are in Steam's metadata (I assume)
• Generated IDs from non-Steam games get ignored entirely
• Renaming the folder to the correct app ID (temporarily to test) doesn't work

Note:

I may be using prefixer incorrectly or misunderstanding how prefix discovery works.
If there is already a supported way to target non-Steam prefixes, please let me know.

[wojtmic]

Have you restarted Steam post-adding the shortcut?

[keygenesis]

Yes, I have. Just tested it with three more different non-Steam shortcuts
(IDs: 2658462558, 2192452658, 3813751565) that I've had for a while as well and all three fail the same way. Steam
games work fine as expected.

[Heus-Sueh]

Yes, I have. Just tested it with three more different non-Steam shortcuts (IDs: 2658462558, 2192452658, 3813751565) that I've had for a while as well and all three fail the same way. Steam games work fine as expected.

The same thing happens here.