WIP: use ui_test dependency builder for test dependencies

[RalfJung]

changelog: none

This tries to make progress on rust-lang/rust#78717 by using the ui_test dependency handling instead of linking in the dependencies of clippy itself with the tests. This effectively reverts #11045.

However, it doesn't quite work. I am getting this:

command: Ok(
    (
        "quote",
        [
            "/home/r/src/rust/clippy/target/ui_test/0/debug/deps/libquote-7d753679308ff16a.rlib",
            "/home/r/src/rust/clippy/target/ui_test/0/debug/deps/libquote-7d753679308ff16a.rmeta",
        ],
    ),
) vs Ok(
    (
        "quote",
        [
            "/home/r/src/rust/clippy/target/ui_test/0/x86_64-unknown-linux-gnu/debug/deps/libquote-d21625b54f8de8ce.rlib",
            "/home/r/src/rust/clippy/target/ui_test/0/x86_64-unknown-linux-gnu/debug/deps/libquote-d21625b54f8de8ce.rmeta",
        ],
    ),
) (["lib"])

full stderr:
registry+https://github.com/rust-lang/crates.io-index#[email protected]
full stdout:
`ui_test` does not support crates that appear as both build-dependencies and core dependencies

I am not sure which exact dependencies ui_test is referring to here -- clippy_test_deps does not have any build-dependencies.

@oli-obk do you know what could be done here?

[rustbot]

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[Alexendoo]

No clue about the ui_test error, but ui-internal tests still depend on clippy_utils

[RalfJung]

Oh I see, and those are driven by the same runner. So depending on the test suite we'll need to use one or the other logic.

[oli-obk]

This effectively reverts #11045.

that PR was made because it was prohibitively slow for many maintainers and contributors to build the deps in the test suite instead of in the main build. I don't see how that issue can be avoided.

[oli-obk]

I am not sure which exact dependencies ui_test is referring to here -- clippy_test_deps does not have any build-dependencies.

@oli-obk do you know what could be done here?

this is about quote, which iirc I could not differentiate in cargo_metadata output by rustc and cargo to properly detect which ones are build as proc macro deps or as direct deps

[RalfJung]

I don't see how that issue can be avoided.

The issue is avoided by noting having the clippy crates in clippy_test_deps. Only the ui-internal tests need them; those will still use the old style of adding dependencies -- which is fine as they don't run in the rustc repo at all.

I didn't implement this part yet; it's what I referred to here.

[RalfJung]

this is about quote, which iirc I could not differentiate in cargo_metadata output by rustc and cargo to properly detect which ones are build as proc macro deps or as direct deps

Ah so the problem is that we pull in serde which pulls in a proc macro which has quote as a proc macro dep? Hm...

They look different in what you print, one is in the x86_64-unknown-linux-gnu folder and one is not. Not sure if there's a good way to use that.

Do clippy tests need serde with the proc macro or could we disable that feature?

[flip1995]

A lot of Clippy tests use derive(Deserialize), which needs those proc macros. The tests/ui/unsafe_derive_deserialize.rs specifically is about this derive attribute.

[RalfJung]

Okay, damn. Then ui_test has to somehow figure out which dependencies belong where...

[oli-obk]

I can give it another shot, but I may have to ask cargo to emit more data

[RalfJung]

I tried to understand the problem and created an issue for further discussion: oli-obk/ui_test#327.