elm-test-rs --watch sometimes gives a _Debug_crash

[yarrow]

When I save a file after a change, I fairly frequently get a crash message from elm-test-rs --watch instead of test output. The workaround is just to save again — elm-test-rs recovers and runs the tests as expected.

I may well have done something wonky in my setup — I'm pretty new to Elm, and very new to elm-test-rs, Lamdera, and Elm Land, which I'm trying to use together.

Here's an example crash message:

Change detected in tests/Tests.elm
==================================





node:internal/event_target:1083
  process.nextTick(() => { throw err; });
                           ^
Error: TODO in module `Runner` on line 33

The regex for replacing this Debug.todo with some real code must have failed since you see this message!

Please report this bug: https://github.com/mpizenberg/elm-test-rs/issues/new

    at _Debug_crash (/Users/yarrow/elm/convergence/elm-stuff/tests-0.19.1/js/Runner.elm.js:498:10)
    at /Users/yarrow/elm/convergence/elm-stuff/tests-0.19.1/js/Runner.elm.js:254:3
    at $author$project$Runner$checkHelperReplaceMe___ (/Users/yarrow/elm/convergence/elm-stuff/tests-0.19.1/js/Runner.elm.js:3325:5)
    at /Users/yarrow/elm/convergence/elm-stuff/tests-0.19.1/js/Runner.elm.js:3990:4
    at Object.<anonymous> (/Users/yarrow/elm/convergence/elm-stuff/tests-0.19.1/js/Runner.elm.js:5194:5)
    at Module._compile (node:internal/modules/cjs/loader:1241:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1295:10)
    at Module.load (node:internal/modules/cjs/loader:1091:32)
    at Module._load (node:internal/modules/cjs/loader:938:12)
    at Module.require (node:internal/modules/cjs/loader:1115:19)
Emitted 'error' event on Worker instance at:
    at [kOnErrorMessage] (node:internal/worker:326:10)
    at [kOnMessage] (node:internal/worker:337:37)
    at MessagePort.<anonymous> (node:internal/worker:232:57)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:807:20)
    at exports.emitMessage (node:internal/per_context/messageport:23:28)

Node.js v20.8.0

[lydell]

This happened a couple of times in a row for me with elm-test --watch (note: not elm-test-rs), but then the next day I couldn’t reproduce it and haven’t been able to since. Spooky.

[mpizenberg]

Spooky indeed, and it seems that's related to the one place we used a regex to patch the generated code. I trusted Harry on this, since I'm no good with regexes and it seemed to work ^^. If you happen to know regexes well, maybe don't hesitate to have a look at the one in this repo. (The error message should help finding where that is). I may have time to have a look at it next weekend.

…

On Sat, Oct 7, 2023, 18:05 Simon Lydell ***@***.***> wrote: This happened a couple of times in a row for me with elm-test --watch (note: not elm-test-rs), but then the next day I couldn’t reproduce it and haven’t been able to since. Spooky. — Reply to this email directly, view it on GitHub <#130 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAWFOCJZ2IRXZZB27UENI7TX6F4V5AVCNFSM6AAAAAA5W7M76CVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTONJRG42DMNBZHE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[yarrow]

The regex looks fine. I suspect thatkernel_patch_tests isn't being executed, since Runner.elm.js also doesn't have console.log changed to console.elmlog after a crash.

I was lucky enough to see a crash while running with -vvv, and did get a log message Kernel-patching Runner.elm.js before the crash. Currently that log happens just before the attempt to read from compiled_runner, so maybe the read fails sometimes? It's I/O, so there could be some kind of weird data race happening.

I've compiled a version that adds a Reading Runner.elm.js before the read and moved Kernel-patching Runner.elm.js into the kernel_patch_tests function.

Of course, now I'm not getting crashes! I'll keep working on my project with the altered logging and -vvv and keep my fingers crossed for more information.