Tracking Issue for minicore (core prelude stubs test auxiliary) #131485

jieyouxu · 2024-10-10T06:24:13Z

Context

We have a bunch of #![no_core] ui/codegen/assembly tests that roll their own core prelude stubs because they need to build (but not run) on a cross-compiled target. But this means:

A bunch of duplicated implementations of core prelude stubs scattered in different tests.
A heavy burden on a contributor of possibly having to update many tests if a new required lang item wants to be added.
Prelude stubs can obfuscate the intent of the test (more things that the reader has to read and mentally filter out).

Instead of continuing to add more copies of core prelude stubs, let's centralize such core prelude stubs into a shared test auxiliary called minicore. minicore is for core prelude stubs specifically. std prelude which can include liballoc items and such is beyond the scope of minicore, because core is usable by more tests. This does not preclude adding another ministd or minialloc for stubs of std/liballoc respectively.

See #130375 for more discussions.

Steps

1. Open an MCP to add minicore test auxiliary.
- MCP is accepted: Support tests to use minicore std/core prelude stubs compiler-team#786
- Note that the MCP title specified std/core prelude stubs, but we revised the scope to core stubs only.
2. Implement initial test infra support for minicore.
- Add minicore test auxiliary and support //@ add-core-stubs directive in ui/assembly/codegen tests #130693
3. Adjust rustc-dev-guide docs.
- Describe minicore test auxiliary and directive rustc-dev-guide#2097
4. ~~Figure out the logistics on how to absorb core stubs into minicore, then use minicore to simplify existing #![no_core] tests.~~
- Currently, I think it's better to just have the infra in place to allow newer and changed tests to use minicore.rs, it seems like unnecessary churn to also force existing tests to use minicore.rs atm.

Unresolved questions

What do we do with existing #![no_core] tests that could benefit from minicore?

The text was updated successfully, but these errors were encountered:

scottmcm · 2024-10-10T15:58:56Z

Great news! I've been doing some MIR work that uses lang items, and ended up just making it work a bit worse instead of dealing with all the no-core tests. If there was a centralized place to deal with problems like this, that'd be great 🎉

Add `minicore` test auxiliary and support `//@ add-core-stubs` directive in ui/assembly/codegen tests Context: [Real cross-compiling tests instead of `#![no_core]` silliness rust-lang#130375](rust-lang#130375) MCP: rust-lang/compiler-team#786 Tracking issue: rust-lang#131485 This prototype PR is subject to further changes based on feedback. ### New `minicore` test auxiliary and `//@ add-core-stubs` compiletest directive This PR introduces a prototype implementation of a `minicore` auxiliary test helper that provides `core` stubs for `#![no_core]` ui/assembly/codegen tests that need to build but not run on both the host platform and the cross-compiled target platform. Key summary: - `tests/auxiliary/minicore.rs` contains stub definitions of `core` items intended for consumption by `check-pass`/`build-pass` tests that want the typical prelude items like `Copy` to be stubbed out under `#![no_core]` scenarios, so that the test can be built (not run) for cross-compiled target platforms. Such tests don't want nor need full `-Z build-std` (e.g. `tests/ui/abi/compatibility.rs`). - `minicore` is intended for `core` items **only**, not `std`- or `alloc`-exclusive items. If stubs for `alloc` or `std` are wanted, they should be provided by an additional directive and test auxiliary, and not be conflated with `minicore` or `core` stubs. This is because a wider range of tests can benefit from `core`-only stubs. ### Implementation - The `minicore` auxiliary is a single source file `tests/auxiliary/minicore.rs`. - The path to `minicore` is made avaiable from bootstrap to compiletest via the `--minicore-path` compiletest flag. - `minicore` is then built on-demand via the `//@ add-core-stubs` compiletest directive, for each test revision for the given target platform (this distinction is important for when host platform != target platform in cross-compilation scenario). - `minicore` is then made available to the test as an [extern prelude]. [extern prelude]: https://doc.rust-lang.org/reference/names/preludes.html#extern-prelude ### Example usage ```rs // tests/ui/abi/my-abi-test.rs //@ check-pass //@ add-core-stubs //@ compile-flags: --target i686-unknown-linux-gnu //@ needs-llvm-components: x86 #![feature(no_core, lang_items)] #![no_std] #![no_core] #![allow(unused, internal_features)] extern crate minicore; use minicore::*; #[lang = "clone"] pub trait Clone: Sized { // `Sized` is provided by `minicore` fn clone(&self) -> Self; } ``` ### Implementation steps - [x] 1. Add an initial `minicore` test auxiliary. - [x] 2. Build `minicore` in bootstrap. - [x] 3. Setup a `--minicore-path` compiletest cli flag and pass `minicore` build artifact path from bootstrap to compiletest. - [x] 4. Assert `add-core-stubs` is mutually incompatible with tests that require to be `run`, as the stubs are only good for tests that only need to be built (i.e. no `run-{pass,fail}`). - [x] 5. Add some self-tests to sanity check the behavior. - [x] 6. Ensure that `tests/auxiliary/minicore.rs` is input stamped, i.e. modifying `tests/auxiliary/minicore.rs` should invalidate test cache and force the test to be rerun. ### Known limitations - The current `minicore` is very minimal, because this PR is intended to focus on supporting the test infrastructure first. Further stubs could be added in follow-up PRs and/or on a as-needed basis. try-job: aarch64-apple try-job: armhf-gnu try-job: x86_64-msvc try-job: test-various try-job: dist-various-1

Rollup merge of rust-lang#130693 - jieyouxu:minicore, r=bjorn3 Add `minicore` test auxiliary and support `//@ add-core-stubs` directive in ui/assembly/codegen tests Context: [Real cross-compiling tests instead of `#![no_core]` silliness rust-lang#130375](rust-lang#130375) MCP: rust-lang/compiler-team#786 Tracking issue: rust-lang#131485 This prototype PR is subject to further changes based on feedback. ### New `minicore` test auxiliary and `//@ add-core-stubs` compiletest directive This PR introduces a prototype implementation of a `minicore` auxiliary test helper that provides `core` stubs for `#![no_core]` ui/assembly/codegen tests that need to build but not run on both the host platform and the cross-compiled target platform. Key summary: - `tests/auxiliary/minicore.rs` contains stub definitions of `core` items intended for consumption by `check-pass`/`build-pass` tests that want the typical prelude items like `Copy` to be stubbed out under `#![no_core]` scenarios, so that the test can be built (not run) for cross-compiled target platforms. Such tests don't want nor need full `-Z build-std` (e.g. `tests/ui/abi/compatibility.rs`). - `minicore` is intended for `core` items **only**, not `std`- or `alloc`-exclusive items. If stubs for `alloc` or `std` are wanted, they should be provided by an additional directive and test auxiliary, and not be conflated with `minicore` or `core` stubs. This is because a wider range of tests can benefit from `core`-only stubs. ### Implementation - The `minicore` auxiliary is a single source file `tests/auxiliary/minicore.rs`. - The path to `minicore` is made avaiable from bootstrap to compiletest via the `--minicore-path` compiletest flag. - `minicore` is then built on-demand via the `//@ add-core-stubs` compiletest directive, for each test revision for the given target platform (this distinction is important for when host platform != target platform in cross-compilation scenario). - `minicore` is then made available to the test as an [extern prelude]. [extern prelude]: https://doc.rust-lang.org/reference/names/preludes.html#extern-prelude ### Example usage ```rs // tests/ui/abi/my-abi-test.rs //@ check-pass //@ add-core-stubs //@ compile-flags: --target i686-unknown-linux-gnu //@ needs-llvm-components: x86 #![feature(no_core, lang_items)] #![no_std] #![no_core] #![allow(unused, internal_features)] extern crate minicore; use minicore::*; #[lang = "clone"] pub trait Clone: Sized { // `Sized` is provided by `minicore` fn clone(&self) -> Self; } ``` ### Implementation steps - [x] 1. Add an initial `minicore` test auxiliary. - [x] 2. Build `minicore` in bootstrap. - [x] 3. Setup a `--minicore-path` compiletest cli flag and pass `minicore` build artifact path from bootstrap to compiletest. - [x] 4. Assert `add-core-stubs` is mutually incompatible with tests that require to be `run`, as the stubs are only good for tests that only need to be built (i.e. no `run-{pass,fail}`). - [x] 5. Add some self-tests to sanity check the behavior. - [x] 6. Ensure that `tests/auxiliary/minicore.rs` is input stamped, i.e. modifying `tests/auxiliary/minicore.rs` should invalidate test cache and force the test to be rerun. ### Known limitations - The current `minicore` is very minimal, because this PR is intended to focus on supporting the test infrastructure first. Further stubs could be added in follow-up PRs and/or on a as-needed basis. try-job: aarch64-apple try-job: armhf-gnu try-job: x86_64-msvc try-job: test-various try-job: dist-various-1

jieyouxu · 2024-10-31T15:56:08Z

Initial test infra PR #130693 has now merged.

This was referenced Oct 11, 2024

Add minicore test auxiliary and support //@ add-core-stubs directive in ui/assembly/codegen tests #130693

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Describe minicore test auxiliary and directive rust-lang/rustc-dev-guide#2097

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Tracking Issue for minicore (core prelude stubs test auxiliary) #131485

Tracking Issue for minicore (core prelude stubs test auxiliary) #131485

jieyouxu commented Oct 10, 2024 •

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scottmcm commented Oct 10, 2024

jieyouxu commented Oct 31, 2024 •

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Tracking Issue for minicore (core prelude stubs test auxiliary) #131485

Tracking Issue for minicore (core prelude stubs test auxiliary) #131485

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jieyouxu commented Oct 10, 2024 • edited Loading

Context

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Unresolved questions

scottmcm commented Oct 10, 2024

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jieyouxu commented Oct 31, 2024 •

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