Add This Month In Our Test Infra Oct 2024 issue

Date range: 2024-10-09 to 2024-11-04.

Author: jieyouxu

posts/inside-rust/2024-11-04-test-infra-oct-2024-2.md

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+---
+layout: post
+title: "This Month in Our Test Infra: October 2024"
+author: Jieyou Xu
+team: the Bootstrap Team <https://www.rust-lang.org/governance/teams/infra#team-bootstrap>
+---
+
+# This Month in Our Test Infra: October 2024
+
+<!-- time period: 2024-10-09 through 2024-11-04 -->
+
+This is a quick summary of the changes in the test infrastructure for the [rust-lang/rust][r-l/r]
+repository[^scope] for **October 2024**[^spec-date]. It also includes brief descriptions of on-going
+work.
+
+[^scope]: The test infra here refers to the test harness [compiletest] and supporting components in
+our build system [bootstrap]. This test infra is used mainly by rustc and rustdoc. Other tools like
+cargo, miri or rustfmt maintain their own test infra.
+[^spec-date]: specifically 2024-10-09 to 2024-11-04. Note that the previous issue incorrectly used
+    October in the filename and thus URL, but is actually the September issue.
+
+As usual, if you encounter bugs or UX issues when using our test infrastructure, please [file an
+issue][new-issue]. Bugs and papercuts can't be fixed if we don't know about them!
+
+**Thanks to everyone who contributed to our test infra!**
+
+## Highlights
+
+### `compiletest` now supports bringing your own custom diff tool
+
+[`compiletest` (and bootstrap) now supports bringing your own custom diff tool
+(#131181)][custom-diff-tool].
+
+![A ui test failure showing stderr snapshot diff produced by a custom differ](../../../../images/2024-11-04-test-infra-oct-2024-2/compiletest-custom-differ.png)
+
+This only affects the *visual* diff generation (i.e. maybe you like a different visual style). The
+`.stderr` snapshots and such are not affected.
+
+If you want to use your favorite diff tool for generating the visual diffs, you can modify
+`config.toml`'s `build.compiletest-diff-tool` option:
+
+```toml
+[build]
+# What custom diff tool to use for displaying compiletest tests.
+#compiletest-diff-tool = <none>
+```
+
+Thanks to [`@dev-ardi`] for the implementation!
+
+[`@dev-ardi`]: https://github.com/dev-ardi
+[custom-diff-tool]: https://github.com/rust-lang/rust/pull/131181
+
+### `minicore` test auxiliary and `//@ add-core-stubs` directive 
+
+[`ui`, `assembly` and `codegen` tests can now use the `//@ add-core-stubs` directive to
+conditionally build a `minicore` test auxiliary which provides `core` stubs
+(#130693)](https://github.com/rust-lang/rust/pull/130693). This is so that we can share `core` stubs
+between cross-compiling tests that only need to *build* for the cross-compile target and avoid
+having to reinvent and maintain duplicate `minicore` copies in each of such test[^multicore].
+
+[^multicore]: You can say we currently have more of a... "multicore" situation, heh.
+
+Previously, having to reinvent a `minicore` every time you want to add a distinct
+`ui`/`assembly`/`codegen` test (for checking e.g. cross-compile ABI) is a significant source of
+contributor friction and makes it more prone to introduce mistakes in the `minicore` copies. This is
+also particularly annoying for compiler contributors who want to introduce new lang items, as they
+found themselves having to update multiple copies of such `core` stubs.
+
+Note that currently, the shared [`tests/auxiliary/minicore.rs`][minicore] test auxiliary is still
+quite minimal. The plan is to land the test infrastructure first, then we can incrementally add more
+`core` stubs to the shared test auxiliary.
+
+Example usage:
+
+```rs
+// tests/ui/abi/my-abi-test.rs
+
+#![crate_type = "lib"]
+#![feature(no_core)]
+#![no_std]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+struct Meow;
+impl Copy for Meow {} // `Copy` is provided by `minicore`!
+```
+
+See the [context issue][minicore-ctxt], [MCP][minicore-mcp] and [tracking issue][minicore-tracking]
+for more info on the original motivations. See the [rustc-dev-guide][minicore-dev-guide] chapter for
+example usage.
+
+[minicore]: https://github.com/rust-lang/rust/blob/master/tests/auxiliary/minicore.rs
+[minicore-ctxt]: https://github.com/rust-lang/rust/issues/130375
+[minicore-tracking]: https://github.com/rust-lang/rust/issues/131485
+[minicore-mcp]: https://github.com/rust-lang/compiler-team/issues/786
+[minicore-dev-guide]: https://rustc-dev-guide.rust-lang.org/tests/minicore.html
+
+## PR listing
+
+### Improvements
+
+- General test infra: [Add `minicore` test auxiliary and support `//@ add-core-stubs` directive in `ui`/`assembly`/`codegen` tests #130693](https://github.com/rust-lang/rust/pull/130693)
+- [compiletest]: [Add test infra to explicitly test rustc with `autodiff`/`enzyme` disabled #131470](https://github.com/rust-lang/rust/pull/131470)
+- [compiletest]: [Special case error message for a `build-fail` test that failed check build #131642](https://github.com/rust-lang/rust/pull/131642)
+- [compiletest]: [Document various parts of compiletest's lib.rs #131679](https://github.com/rust-lang/rust/pull/131679)
+- [compiletest]: [Fix unnecessary nesting in run-make test output directories #131764](https://github.com/rust-lang/rust/pull/131764)
+- [compiletest]: [Warn on redundant --cfg directive when revisions are used #131925](https://github.com/rust-lang/rust/pull/131925)
+- [compiletest]: [Disambiguate html-tidy from rust tidy tool #131941](https://github.com/rust-lang/rust/pull/131941)
+- [compiletest]: [Custom differ #131181](https://github.com/rust-lang/rust/pull/131181)
+- [compiletest]: [Don't allow test revisions that conflict with built in `cfg`s #131930](https://github.com/rust-lang/rust/pull/131930)
+- [compiletest]: [Dynamically link run-make support #132225](https://github.com/rust-lang/rust/pull/132225)
+- [compiletest]: [Improve robustness of LLVM version handling #132315](https://github.com/rust-lang/rust/pull/132315)
+- [compiletest]: [Add "reference" as a known compiletest header #131382](https://github.com/rust-lang/rust/pull/131382)[^spec]
+- `tests/run-make`, CI: [Add `aarch64-gnu-debug` job #131207](https://github.com/rust-lang/rust/pull/131207)
+- meta: [Tag PRs affecting compiletest with A-compiletest #131682](https://github.com/rust-lang/rust/pull/131682)
+
+[^spec]: This is part of T-spec efforts to associate tests with Reference rules.
+
+### Fixes
+
+- [compiletest]: [Fix up-to-date checking for run-make tests #131681](https://github.com/rust-lang/rust/pull/131681)
+- [compiletest]: [Suppress Windows Error Reporting (WER) for run-make tests](https://github.com/rust-lang/rust/pull/132093)[^wer-fun]
+- [compiletest]: [Error on trying to use revisions in run-make tests #131614](https://github.com/rust-lang/rust/pull/131614)
+- `tests/run-make`, CI: [Run the full stage 2 `run-make` test suite in `x86_64-gnu-debug` #131917](https://github.com/rust-lang/rust/pull/131917)
+- [bootstrap], `tests/run-make`: [Don't stage-off to previous compiler when CI rustc is available #132006](https://github.com/rust-lang/rust/pull/132006)
+- [bootstrap], `tests/mir-opt`: [Match std `RUSTFLAGS` for host and target for `mir-opt` test suite to fix double std build/rebuilds #131442](https://github.com/rust-lang/rust/pull/131442) 
+- emscripten: Fix [bootstrap] and [compiletest] handling of emscripten target tests as part of [Fix most ui tests on emscripten target #131705](https://github.com/rust-lang/rust/pull/131705)
+
+[^wer-fun]: If you want to see what unsuppressed Windows Errors Reporting looks like for the `run-make` test suite, see <https://github.com/rust-lang/rust/issues/132092#issuecomment-2436615833>.
+
+### Cleanups
+
+- [compiletest]: [Extract auxiliary-crate properties to their own module/struct #131541](https://github.com/rust-lang/rust/pull/131541)
+- [compiletest]: [Rename directive `needs-profiler-support` to `needs-profiler-runtime` #131429](https://github.com/rust-lang/rust/pull/131429)
+- [compiletest]: [Move debugger setup code out of lib.rs #131638](https://github.com/rust-lang/rust/pull/131638)
+- [compiletest]: [Remove the one thing that was checking a directive's original_line #131585](https://github.com/rust-lang/rust/pull/131585)
+- [compiletest]: [Store test collection context/state in two structs #131870](https://github.com/rust-lang/rust/pull/131870)
+- [compiletest]: [Tidy up how tidy and tidy (html version) are disambiguated #131961](https://github.com/rust-lang/rust/pull/131961)
+- [compiletest]: [Make `line_directive` return a `DirectiveLine` #132033](https://github.com/rust-lang/rust/pull/132033)
+- [compiletest]: [Rename `command-list.rs` to `directive-list.rs` #132313](https://github.com/rust-lang/rust/pull/132313)
+- [compiletest]: [Remove the magic hacks for finding output with `lto=thin` #131524](https://github.com/rust-lang/rust/pull/131524)
+- [compiletest]: [Simplify the choice of `--emit` mode for assembly tests #131525](https://github.com/rust-lang/rust/pull/131525)
+- [compiletest]: [Move debugger setup code out of lib.rs #131638](https://github.com/rust-lang/rust/pull/131638)
+
+### Documentation updates
+
+- [rustc-dev-guide]: [Document compiletest directives `ignore-coverage-map` and `ignore-coverage-run` #2094](https://github.com/rust-lang/rustc-dev-guide/pull/2094)
+- [rustc-dev-guide]: [Rename `needs-profiler-support` to `needs-profiler-runtime` #2095](https://github.com/rust-lang/rustc-dev-guide/pull/2095)
+- [rustc-dev-guide]: [Fix and update docs for `needs-force-clang-based-tests` #2085](https://github.com/rust-lang/rustc-dev-guide/pull/2085)
+- [rustc-dev-guide]: [Add redirects for integration-testing and headers #2092](https://github.com/rust-lang/rustc-dev-guide/pull/2092)
+- [rustc-dev-guide]: [Describe minicore test auxiliary and directive #2097](https://github.com/rust-lang/rustc-dev-guide/pull/2097)
+- [rustc-dev-guide]: [Fix minicore.rs link #2122](https://github.com/rust-lang/rustc-dev-guide/pull/2122)
+- [rustc-dev-guide]: [Add a link for the `reference` compiletest header #2096](https://github.com/rust-lang/rustc-dev-guide/pull/2096)
+
+## On-going efforts
+
+Note: there are certainly many more spontaneous efforts, this is more what I know is "planned".
+
+- [Reworking `compiletest` directive handling to be more robust and improve test coverage](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/.28Rubberducking.29.20compiletest.20test.20discovery.20.2F.20directives)
+
+
+[r-l/r]: https://github.com/rust-lang/rust
+[rustc-dev-guide]: https://github.com/rust-lang/rustc-dev-guide
+[compiletest]: https://github.com/rust-lang/rust/tree/master/src/tools/compiletest
+[bootstrap]: https://github.com/rust-lang/rust/tree/master/src/bootstrap
+[new-issue]: https://github.com/rust-lang/rust/issues/new