Use the same filename hash for pre-release channels. #8073
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cc @Mark-Simulacrum This may just fix rust-lang/rust#69060 wholesale. |
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So when I switch back and forth between a nightly and something installed via rustup-toolchain-install-master, this will do a full rebuild on each switch? |
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Yes, it'll cause a rebuild. Let me know if you think that will be too annoying. One workaround is to use something like |
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No I think it's okay I think, I don't swap back and forth in the same checkout too often. |
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Seems reasonable to me implementation and feature-wise, thanks for this @ehuss! (and nice test too btw) I'll leave this for a bit more to see if others have thoughts on it but otherwise r=me at any time |
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I added a |
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@bors: r+ |
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📌 Commit fdfdb3d has been approved by |
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☀️ Test successful - checks-azure |
Update cargo 12 commits in 390e8f245ef2cd7ac698b8a76abf029f9abcab0d..74e3a7d5b756d7c0e94399fc29fcd154e792c22a 2020-04-07 17:46:45 +0000 to 2020-04-13 20:41:52 +0000 - Update dependencies to support illumos target (rust-lang/cargo#8093) - Whitelist another known spurious curl error (rust-lang/cargo#8102) - Fix nightly test matching rustc "warning" output. (rust-lang/cargo#8098) - Update default for codegen-units. (rust-lang/cargo#8096) - Fix freshness when linking is interrupted. (rust-lang/cargo#8087) - Add `cargo tree` command. (rust-lang/cargo#8062) - Add "build-finished" JSON message. (rust-lang/cargo#8069) - Extend -Zpackage-features with more capabilities. (rust-lang/cargo#8074) - Disallow invalid dependency names through crate renaming (rust-lang/cargo#8090) - Use the same filename hash for pre-release channels. (rust-lang/cargo#8073) - Index the commands section (rust-lang/cargo#8081) - Upgrade to mdBook v0.3.7 (rust-lang/cargo#8083)
rust-lang/cargo#8073 has long since hit beta, so we no longer need this step in perf. It's also true that rust-src is currently incomplete so we can't build std in perf regardless.
This changes it so that filenames do not hash the entire verbose version from rustc if they are a pre-release version. The intent is to avoid leaving stale artifacts in the target directory whenever someone updates a nightly or beta release. This should help reduce disk space usage for someone who updates these toolchains frequently.
I tested with the rustc repo, and it seems to be OK. It keeps everything in separate target directories, so I think it should be generally safe. This should only affect someone switching between different nightlies and wanting to avoid recompiling when switching back. I suspect that is a rare use case, though if there are complaints this can be easily reverted (or made a config option). cargo-bisect-rustc should also be safe since it uses a different target directory for each toolchain.
One concern here for me was incremental support. It looks like (src) the incremental cache includes the detailed rustc version, so I think that is safe. It also looks like it is smart enough to delete stale files.
We will need to be more careful in the future when changing the target directory structure or the format of files. We previously relied on the fact that each new nightly will use different filenames. If we change the structure in a backwards-incompatible way, we will need to be careful to update the version (
1.hashincompute_metadata).