conjure-cp-rules relating to grammar changes

[leiamcalisteryoung]

I am running into the issue once again where if I change anything in the grammar, I get loads of errors coming from files in crates/conjure-cp-rules/src/, mostly from the matrix and normalizers folder. I am not sure who worked on this or if I am doing something wrong here. Does anyone know whats going on or who might know the answer? @conjure-cp/vip-students

[niklasdewally]

Are these compiler errors or runtime panics?

If it is the latter, could you list which tests fail?

[niklasdewally]

Have you seen this issue by @gskorokhod:
#1049

[gskorokhod]

TL;DR:

⚠️ If you're getting unrelated compiler errors after changing the parser code, it means the parser is broken.
Fixing the parser will also fix these errors.
Integration tests will not work until you fix the parser.
This is a known limitation.

essence_expr! macros call the parser at compile time. If the parser is broken for whatever reason (e.g. when you change the treesitter grammar, but haven't fully updated the Rust side of the parser yet), macros will fail to expand and cause compile time errors throughout the project.

The solution is to write dedicated parser tests inside the conjure-cp-essence-parser crate, and use these to debug the parser;
Then, when the parser works (at least to the point of "being able to parse a simple Expression without panicking"), you can run the integration test suite and check that the parser changes haven't caused any subtle bugs in our rewriter rules etc.

Long term, we should:

1. Write a dedicated test harness for just the parser, which uses the same Essence files as our integration tests but only does the parse step (not the rewriting / solving steps). This is tracked in Dedicated parser tests #1055.
2. Be smart with our build.rs scripts to only build conjure-cp-rules (and everything that depends on it) if the parser tests pass (just to avoid having a lot of seemingly unrelated compiler errors when the parser is broken). This is tracked in Do not try to build integration tests unless all parser tests pass #1049.

[gskorokhod]

leaving this here for future reference :)