Suggested workflow for vscode check-on-save can lead to surprisingly expensive check builds #141955
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A-contributor-roadblock
Area: Makes things more difficult for new or seasoned contributors to Rust
T-bootstrap
Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)
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implement new `x` flag: `--skip-std-check-if-no-download-rustc` One of our developers (`@RalfJung)` [reported](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Surprising.20stages.20for.20check.20build.20after.20stage.20reorg/with/521925606)[#t-infra/bootstrap > Surprising stages for check build after stage reorg](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Surprising.20stages.20for.20check.20build.20after.20stage.20reorg/with/521925606) that working on both the compiler and the library simultaneously with RA enabled is extremely difficult because checking library creates a heavy load on machines (by building stage1 compiler) on each modification. `--skip-std-check-if-no-download-rustc` flag is intended to reduce this heavy load on their IDE integration as much as possible. Fixes: rust-lang#141955
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Rollup merge of #141970 - onur-ozkan:skip-stage1-std, r=Kobzol implement new `x` flag: `--skip-std-check-if-no-download-rustc` One of our developers (``@RalfJung)`` [reported](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Surprising.20stages.20for.20check.20build.20after.20stage.20reorg/with/521925606)[#t-infra/bootstrap > Surprising stages for check build after stage reorg](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Surprising.20stages.20for.20check.20build.20after.20stage.20reorg/with/521925606) that working on both the compiler and the library simultaneously with RA enabled is extremely difficult because checking library creates a heavy load on machines (by building stage1 compiler) on each modification. `--skip-std-check-if-no-download-rustc` flag is intended to reduce this heavy load on their IDE integration as much as possible. Fixes: #141955
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With the stage 0 redesign,
./x checknow (sometimes?) defaults to stage 1. If a downloaded rustc cannot be used, this command is quite expensive: it does a full rustc build, and then checks everything! That's not what users expect from a check build (which is supposed to be quick). It's also bad when you are on battery -- it's a nasty surprise when you realize that just opening vscode sucked up 8% of your battery as it did a full rustc build.I don't know what the best fix here, but I think it is a hard requirement for the suggested check-on-save command that it never does an actual full compiler build. This was true with the old staging, and we should make sure it becomes true again.
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