src/tests/stdlib-semver-check.md - rust-lang/rustc-dev-guide - Git at Google

 # Standard library semantic versioning breakage check

 The `test-x86_64-gnu-stdlib-semver-check` job runs the [`cargo-semver-checks`][csc] (c-s-c) tool on the standard library (`core`, `alloc` and `std`) in order to find potential unintended semantic versioning (semver) breakages.
 It does so by analyzing the rustdoc JSON output (from the `rust-docs-json` component) of the parent merge commit, and the current commit being merged.
 When it runs, one of five things can happen:

 1. Everything proceeds correctly, c-s-c does not find any breakage.
 2. The rustdoc JSON version was bumped recently, and c-s-c cannot handle it yet.
    This case will result in the test ending with a success,
    and printing a warning that c-s-c needs to be updated.
    Once c-s-c releases a version that supports the new JSON format, it should go to 1. again.
    - We currently install the latest released version of c-s-c in this job,r
      so its version does not need to be updated manually in the `rust-lang/rust` repository.
 3. c-s-c detects a breakage, but it is a false positive.
    In this case, please report the false positive to [this Zulip topic][semver-topic],
 and [bump the stamp file](#bumping-the-stdlib-semver-stamp-file).
 4. c-s-c detects a real breakage, and it helped you find unintended beakage.
    Yay!
    In this case, please consider reporting the success to [this Zulip topic][semver-topic].
 5. c-s-c detects a real breakage, but you want to land it anyway (maybe it is an edge case that was FCPed).
    In that case, [bump the stamp file](#bumping-the-stdlib-semver-stamp-file).

 ## Bumping the stdlib semver stamp file

 If you want to let CI pass on a PR where c-s-c detects breakage (whether it is real or not),
 you have to modify the `src/bootstrap/stdlib-semver-check-stamp` file.
 Please update the PR number in which you modify this file at the bottom of the file.
 This will ensure that the test will stay green, regardless of what c-s-c detects.

 ## Running the check manually

 You can manually run the semver check locally using `./x test std-semver-check --set rust.stdlib-semver-baseline=${PARENT}`,
 where `PARENT` is a commit SHA against which you want to compare the in-tree stdlib.
 If you do not specify it,
 bootstrap will select the latest upstream commit that it finds in your local git history.

 [semver-topic]: https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Breakages.20detected.20by.20cargo-semver-checks/with/615570111
 [csc]: https://github.com/obi1kenobi/cargo-semver-checks
	# Standard library semantic versioning breakage check

	The `test-x86_64-gnu-stdlib-semver-check` job runs the [`cargo-semver-checks`][csc] (c-s-c) tool on the standard library (`core`, `alloc` and `std`) in order to find potential unintended semantic versioning (semver) breakages.
	It does so by analyzing the rustdoc JSON output (from the `rust-docs-json` component) of the parent merge commit, and the current commit being merged.
	When it runs, one of five things can happen:

	1. Everything proceeds correctly, c-s-c does not find any breakage.
	2. The rustdoc JSON version was bumped recently, and c-s-c cannot handle it yet.
	This case will result in the test ending with a success,
	and printing a warning that c-s-c needs to be updated.
	Once c-s-c releases a version that supports the new JSON format, it should go to 1. again.
	- We currently install the latest released version of c-s-c in this job,r
	so its version does not need to be updated manually in the `rust-lang/rust` repository.
	3. c-s-c detects a breakage, but it is a false positive.
	In this case, please report the false positive to [this Zulip topic][semver-topic],
	and [bump the stamp file](#bumping-the-stdlib-semver-stamp-file).
	4. c-s-c detects a real breakage, and it helped you find unintended beakage.
	Yay!
	In this case, please consider reporting the success to [this Zulip topic][semver-topic].
	5. c-s-c detects a real breakage, but you want to land it anyway (maybe it is an edge case that was FCPed).
	In that case, [bump the stamp file](#bumping-the-stdlib-semver-stamp-file).

	## Bumping the stdlib semver stamp file

	If you want to let CI pass on a PR where c-s-c detects breakage (whether it is real or not),
	you have to modify the `src/bootstrap/stdlib-semver-check-stamp` file.
	Please update the PR number in which you modify this file at the bottom of the file.
	This will ensure that the test will stay green, regardless of what c-s-c detects.

	## Running the check manually

	You can manually run the semver check locally using `./x test std-semver-check --set rust.stdlib-semver-baseline=${PARENT}`,
	where `PARENT` is a commit SHA against which you want to compare the in-tree stdlib.
	If you do not specify it,
	bootstrap will select the latest upstream commit that it finds in your local git history.

	[semver-topic]: https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Breakages.20detected.20by.20cargo-semver-checks/with/615570111
	[csc]: https://github.com/obi1kenobi/cargo-semver-checks