[CI] Check semver compatibility with all target platforms, not just the host platform

[joshlf]

We use cargo-semver-checks-action in CI to ensure we do not accidentally break semver compatibility:

zerocopy/.github/workflows/ci.yml

Lines 244 to 264 in 0ff2dd1

	# Check semver compatibility with the most recently-published version on
	# crates.io. We do this in the matrix rather than in its own job so that it
	# gets run on different targets. Some of our API is target-specific (e.g.,
	# SIMD type impls), and so we need to run on each target.
	#
	# TODO(https://github.com/obi1kenobi/cargo-semver-checks-action/issues/54):
	# Currently we don't actually do anything with `matrix.target`, so we're
	# just duplicating work by running this job multiple times, each time
	# targetting the host platform.
	- name: Check semver compatibility
	uses: obi1kenobi/cargo-semver-checks-action@v2
	with:
	# Don't semver check zerocopy-derive; as a proc macro, it doesn't have
	# an API that cargo-semver-checks can understand.
	package: zerocopy
	feature-group: all-features
	# TODO: Set this to the specific nightly we have pinned in CI. Not a big
	# deal since this isn't affected by the trybuild stderr files, which is
	# the reason we need to pin to a specific nightly.
	rust-toolchain: nightly
	if: matrix.crate == 'zerocopy' && matrix.features == '--all-features' && matrix.toolchain == 'nightly'

This check occurs within our build matrix, so it's re-run for each target:

zerocopy/.github/workflows/ci.yml

Lines 41 to 53 in 0ff2dd1

	target: [
	"i686-unknown-linux-gnu",
	"x86_64-unknown-linux-gnu",
	"arm-unknown-linux-gnueabi",
	"aarch64-unknown-linux-gnu",
	"powerpc-unknown-linux-gnu",
	"powerpc64-unknown-linux-gnu",
	"riscv64gc-unknown-linux-gnu",
	"mips-unknown-linux-gnu",
	"mips64-unknown-linux-gnuabi64",
	"s390x-unknown-linux-gnu",
	"wasm32-wasi"
	]

However, we aren't actually making use of target, meaning we are re-running the exact same check 11 times on the Github Actions host target (x86_64-unknown-linux-gnu).

We need to modify this CI job to respect the value of target. To do this, see here: obi1kenobi/cargo-semver-checks-action#54 (comment)

[Sh0g0-1758]

Hello, @joshlf @jswrenn . Can you please assign me this issue. I am interested in working on this.

[joshlf]

Thanks @Sh0g0-1758! Assigned.

[memark]

I've started looking into this. I made some additional comments in the linked issue obi1kenobi/cargo-semver-checks-action#54

I basically see three ways forward here:

• get cargo-semver-checks-action to add a pass-thru property in the form of target
• not use the action; install, build and run cargo semver-checks --target ourselves
• add a .cargo/config file with [build] target = ... to the downloaded repo before running the action (I only tried this briefly, but the file at least appears to be respected.)

[joshlf]

Based on obi1kenobi/cargo-semver-checks-action#54 (comment), I think that a PR to cargo-semver-checks-action is the way to go. If that turns out to be unexpectedly difficult, it wouldn't be a huge deal for us to just use cargo semver-checks --target directly. Thanks for investigating this!

[memark]

Update:
My PR in that repo was merged today. I'll have a look at the associated cache key bug as well, and then I'll come back to finally solve this issue.