Toy brainf**k interpreter; example app that can be modified without restarting

_yet another_ bugfix to the version check X-(

When I stopped running the version check before the tests I also stopped initializing Version, which can be used in tests to watch out for font changes across versions. As a result I started seeing a test failure with LÖVE v12.

It looks like all manual tests pass now. And we're also printing the warning about version checks before running tests, which can come in handy if a new version ever causes test failures. The only thing that makes me unhappy is the fact that we're calling the version check twice. And oh, the fact that this part around initialization and version management is clearly still immature.

I'll capture some desires and fragmentary thought processes around them:

  • If there's an error, go to the source editor.

  • But oh, don't go to source editor on some unactionable errors, so we include a new Current_app mode for them:

    • Unsupported version requires an expert. Just muddle through if you can or give a warning someone can send me.
    • A failing test might be spurious depending on the platform and font rendering scheme. So again just provide a warning someone can send me.

    [Source editor can be confusing for errors. Also an editor! But not showing the file you asked for!]

  • But our framework clears the warning after running tests:

    • If someone is deep in developing a new feature and quits -> restore back in the source editor.

    [Perhaps Current_app is the wrong place for this third hacky mode, since we actually want to continue running. Perhaps it's orthogonal to Current_app.]

    [Ideally I wouldn't run the tests after the version check. I'd pause, wait for a key and then resume tests? "Muddle through" is a pain to orchestrate.]

  • We store Current_app in settings. But we don't really intend to persist a Current_app of 'error'. Only the main app or 'source' editor.

    [Another vote against storing 'error' in Current_app.]

  • So we need to rerun the version check after running tests to actually show the warning.

    [Perhaps I need to separate out the side-effect of setting Version from the side-effect of changing Current_app. But that's not right either, because I do still want to raise an error message if the version check fails before running tests. Which brings us back to wanting to run the tests after raising the version check..]

One good thing: none of the bugs so far have been about silently ignoring test failures. I thought that might be the case for a bit, which was unnerving.

I grew similar muddiness in Mu's bootstrap system over time, with several surrounding modes around the core program that interacted poorly or at least unsatisfyingly with each other. On one level it just feels like this outer layer reflects muddy constraints in the real world. But perhaps there's some skill I still need to learn here..

Why am I even displaying this error if we're going to try to muddle through anyway? In (vain) hopes that someone will send me that information. It's not terribly actionable even to me. But it's really intended for when making changes. If a test fails then, you want to know.

The code would be cleaner if I just threw an unrecoverable error from the version check. Historically, the way I arrived at this solution was:

  • I used the default love.errorhandler for a while
  • I added xpcall and error recovery, but now I have situations where I would rather fall back on love.errorhandler. How to tell xpcall that? But no, this whole line of thought is wrong. LÖVE has a precedent for trying to muddle through on an unexpected version. And spurious test failures don't merit a hard crash. There's some irreducible requirement here. No point making the code simplistic when the world is complex.

Perhaps I should stop caching Version and just recompute it each time. It's only used once so far, hardly seems worth the global.

We have two bits of irreducible complexity here:

  • If tests fail it might be a real failure, or it might not.
  • Even if it's an unexpected version, everything might be fine. And the major remaining problem happens at the intersection of these two bits. What if we get an unexpected version with some difference that causes tests to fail? But this is a hypothetical and not worth thinking about since I'll update the app fairly quickly in response to new versions.

Created by  akkartik  on December 6, 2023
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