Announcing Elm-reduce

#1

Hi! I’ve made a topic about Elm-reduce before, in which I’ve been looking for projects to test Elm-reduce on, now it’s ready for release!

This project helps you create bug reports in case the compiler crashes by removing irrelevant source code from your project until a small test case that reproduces the bug you have remains.

There is more info about this project in the readme on gitlab: https://gitlab.com/matheus23/elm-reduce

If you want a more detailed look at Elm-reduce, you can look at the thesis I wrote about it: https://pp.ipd.kit.edu/publication.php?id=pkrueger19bachelorarbeit (there is a pdf download link on that site)

Please try it out on the next bug that crashes any Elm tool :wink:

Also: I think we could really improve the Elm compiler’s robustness and tooling by fuzz testing the compiler. Elm-reduce is one of the pieces necessary for that: It would reduce the fuzzed test cases that triggered a bug in the compiler. The other piece, the fuzzer, is still missing. Other languages achieve great results by fuzz-testing their compilers: http://embed.cs.utah.edu/csmith/ for C or https://github.com/googleprojectzero/fuzzilli for javascript (testing V8 at google)

What do you think?

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#2

I was checking over the repo just yesterday, didn’t realise you were so close to release!

Just built and ran it against the floorplan example repo I gave you a while back, but hit a snag before it finished:

elm-reduce: Module Not Found: SumAnimateTransform
CallStack (from HasCallStack):
error, called at src/Language/Elm/ModuleDependencies.hs:81:13 in elm-reduce-1.0.0.0-GTrzPXFkMsWAYV3rgntIGt:Language.Elm.ModuleDependencies

Is that something I’m missing on my end, or is this something that was accidentally omitted from the install script?

#3

Interesting!
What is the output of elm make for your project? It seems like it can’t resolve the “SumAnimateTransform” module, I guess it exists :smiley: If you could create an issue in the repository with a zip of your test case that would be awesome! :slight_smile:

#4 
> elm make src/Main.elm --output=elm.js
Success! Compiled 1 module.

Sure thing! I’ll write that up now.

#5

Ah. Found why it’s happening:

./vendored-libs/elm-community/typed-svg/5.0.1/src/Examples/SumAnimateTransform.elm

It’s trying to pull in an example file. Not sure how to overcome this, but we’ll move this conversation to the issue.

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#6

Obviously this is a bug I have to fix, but you can still check out an example if you want to test the project by skipping the vendoring pass via the --no-vendoring flag.

#7

Yep, that runs! But reduces to practically nothing since the Map! error I’m playing with here comes from a package.

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#8

True. It should just be a Main function with a single import and a referred opaque type. That is one of the test Casey that reproduce the Map.! bug.

Even if you enabled vendoring, the library likely couldn’t be added to the source-directory as the bug would then stop reproducing.

I’ll try to fix the bug and we’ll see how it goes! :slight_smile: