parse linter config with cargo metadata

[DaAlbrecht]

Implementation for parsing out the linter config with cargo-metadata #334.

I personally prefer deserializing the Cargo.toml to toml and then parsing the metadata out over this. I can add some performance comparisons if needed, but I expect the cargo-metadata implementation to be way slower.

Some Observations:

1. We need to create a linter config for each package that contains the workspace config (if present) merged with that package's config.

But the bevy_lint_driver is called for each crate target, meaning we could build the same config multiple times.

2. Its "trickier" to get the metadata of the current package because we can not know that package's name.

In this repository: https://github.com/TimJentzsch/bevy_complex_repo/tree/main

❯ cargo metadata --no-deps | jq

lists all packages in this workspace, but from where do we know which of these we should read the metadata table from?

but with

 ❯ cargo metadata --format-version 1 | jq -r '
  .packages[] as $pkg
  | select($pkg.id == .resolve.root)
  | $pkg.name'
cplx_demo

We always get the "current" package but have additional overhead.

3. The resulting code in the end is more or less identical, with the difference that in my opinion, toml is easier to work with for us and we need to depend on it anyway

[BD103]

After skimming over the changes, I agree that this probably isn't worth it. While this does let us remove the dependency on toml, the added logical complexity isn't worth it in my opinion. Also, depending on how rust-lang/rfcs#3808 shapes up, we may still need to parse the TOML anyways for the time being. Thanks for trying this out!

[DaAlbrecht]

After skimming over the changes, I agree that this probably isn't worth it. While this does let us remove the dependency on toml, the added logical complexity isn't worth it in my opinion. Also, depending on how rust-lang/rfcs#3808 shapes up, we may still need to parse the TOML anyways for the time being. Thanks for trying this out!

Yea and we need toml anyway for the cargo lint😄