Stabilize flags for doctest cross compilation

[ehuss]

This makes the following changes in preparation for supporting doctest cross-compiling in cargo:

• Renames --runtool and --runtool-arg to --test-runtool and --test-runtool-arg to maintain consistency with other --test-* arguments.
• Stabilizes the --test-runtool and --test-runtool-arg. These are needed in order to support cargo's target.runner option which specifies a runner to execute a cross-compiled doctest (for example, qemu).
• Stabilizes the --enable-per-target-ignores flag by removing it and making it unconditionally enabled. This makes it possible to disable a doctest on a per-target basis, which I think will be helpful for rolling out this feature.

These changes were suggested in https://rust-lang.zulipchat.com/#narrow/channel/266220-t-rustdoc/topic/stabilizing.20doctest.20xcompile/near/409281127

The intent is to stabilize the doctest-xcompile feature in cargo. This will help ensure that for projects that do cross-compile testing that their doctests are also covered. Currently there is a somewhat surprising behavior that they are ignored.

Closes #64245

try-job: x86_64-msvc-1

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[rustbot]

This PR modifies tests/run-make/. If this PR is trying to port a Makefile
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cc @jieyouxu

The Miri subtree was changed

cc @rust-lang/miri

[bors]

☔ The latest upstream changes (presumably #138830) made this pull request unmergeable. Please resolve the merge conflicts.

[ehuss]

@fmease @GuillaumeGomez Just checking if this can be put on the team's radar?

[GuillaumeGomez]

On my review list now. :)

[GuillaumeGomez]

I think they've been around for enough time. Let's start an FCP then.

@rfcbot fcp merge

[rfcbot]

Team member @GuillaumeGomez has proposed to merge this. The next step is review by the rest of the tagged team members:

• @GuillaumeGomez
• @Manishearth
• @Nemo157
• @aDotInTheVoid
• @camelid
• @fmease
• @jsha
• @notriddle

Concerns:

• forwarding-multi-args-mechanism (Stabilize flags for doctest cross compilation #137096 (comment))

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

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[ehuss]

In playing around with this, I noticed a slight annoyance when using --edition=2024 and mergeable tests. It always prints:

WARNING: No rustdoc doctest environment variable provided so doctests will be run in the same process

I'm wondering if it would make sense to somehow silence that warning when using --test-runtool?

I'm also wondering if it is the right choice to run in the same process. I could see arguments either way. Let me know if you have any opinion on that.

[fmease]

@rfcbot concern forwarding-multi-args-mechanism

I'd like to block this FCP on a concern I have. Together with the unstable --doctest-compilation-args flag, rustdoc now has (at least) three flags used for forwarding program arguments each of which uses a different mechanism:

1. --test-args (stable): Splits its argument by Unicode whitespace
2. --test-runtool-arg (still unstable): Forwards its argument as is
3. --doctest-compilation-args (unstable): Splits its argument "shell-style"

(All of them can be passed multiple times)

---

I'd like to see this rectified.

[ehuss]

@fmease Can you say more about what you would like to see rectified?

--test-runtool-arg has exactly the behavior we want. We need to be able to pass arguments in without needing to do any processing. I would argue that it is unfortunate that --test-args splits on spaces, since it prevents passing args with spaces, but unfortunately that is stable. I don't know why --doctest-compilation-args is using shell quoting, but that won't work for us (and is generally awkward to use, since you may need to double-encode when using a shell).

[fmease]

Right, it's not something I expect you personally to need to answer, it's more directed toward the team, something I wanted to bring attention to because I only realized this yesterday while reviewing and I don't know if the others were aware of that already of not.

To make this more actionable, I think I simply want confirmation from the other T-rustdoc members that we should do something here, namely either

1. What I initially leaned towards but like less now come to think about it:
   1. Use shell-like lexing for --test-args instead of Unicode whitespace splitting (breaking change)
   2. Change --test-runtool-arg to --test-runtool-args and use shell-like lexing for it, too
2. What I now think is the 'best' option:
   1. Keep --test-runtool-arg as is — unblocking this FCP
   2. (Separately) deprecate the stable --test-args in favor of a new --test-arg that doesn't perform any processing
   3. (Separately) replace the unstable --doctest-compilation-args with a new --doctest-build-arg that doesn't perform any processing either

[GuillaumeGomez]

We have a rustdoc meeting in two weeks so we can talk about it then if needed.