fix: Search for grammar file from CARGO_MANIFEST_DIR

[Nukesor]

This is a proposeal to fix #325.

The new logic looks for the [grammar = "$path"] path in CARGO_MANIFEST_DIR/ before using the fallback of CARGO_MANIFEST_DIR/src.

This allows projects that don't have a src folder to use a grammar file, while staying backward compatible.

Alternative implementation approach:

One could theoretically use the absolute function.
Sadly, this function is still nightly, which makes this approach unfeasible.

Current workarounds:

• Restructure the project so it has a src folder
• Create a stub src folder, so one can use relative paths
• Inline all of the grammar via grammar_inline

[tomtau]

thanks! I think that works -- it seems both options are covered by tests, so it should be fine. CC @MarijnS95 this fix should be backwards-compatible, but you can have a quick look.

[tomtau]

maybe can add a TODO with a link to https://doc.rust-lang.org/std/path/fn.absolute.html ?

[Nukesor]

Done :)

[Nukesor]

Hey @tomtau :)

I kind of need this fix for a feature I currently work on. It's a bit tricky to work with this, as pest-meta needs some special handling when building the project with a patched source.
It would be great to get a patch release that contains this fix. Do you have a rough timeline when the next release is planned?

Thanks in advance!

[tomtau]

@Nukesor I think it's all right to make a quick point release after this is merged (plus perhaps after one small issue fix): #705 (to test the fixed CI release flow).

[Nukesor]

Awesome, thanks for your swift response and for taking care of this project :)

[MarijnS95]

CC @MarijnS95 this fix should be backwards-compatible, but you can have a quick look.

@tomtau Fwiw I haven't looked into pest in detail but only got blocked on the previous release accidentally breaking transitive dependencies while updating them. Any contributor that intends to make such changes as part of a patch release should make sure to (build-)test those broken crates to make sure this change can safely be made without a breaking release.

[tomtau]

@Nukesor it's out now: https://crates.io/crates/pest/2.3.1

@MarijnS95 I included this flow using cargo-semver-checks https://github.com/pest-parser/pest/blob/master/semvercheck.sh to check it didn't introduce (API-level) breaking changes, but it wouldn't probably catch that v2.2.0 breaking change (it'd catch the one in v2.2.1 though).

[MarijnS95]

@tomtau Indeed, those checks are nice to have but wouldn't have caught the build failure in external crates. That said, the recent update doesn't prevent any of my crates from building so we're all good here 🎉