Remove `ENABLE_DOWNLOAD_RUSTC` constant
`ENABLE_DOWNLOAD_RUSTC` was introduced as part of the MVP for `download-rustc` as a way not to rebuild artifacts that have already been downloaded. Unfortunately, it doesn't work very well:
- Steps are ignored by default, which makes it easy to leave out a step
that should be built. For example, the MVP forgot to enable any tests,
so it was only possible to *build* locally.
- It didn't work correctly even when it was enabled: calling
`builder.ensure()` would completely ignore the constant and rebuild the
step anyway. This has no obvious fix since `ensure()` has to return a
`Step::Output`.
Instead, this handles `download-rustc` in `impl Step for Rustc` and
`impl Step for Std`, which to my knowledge are the only build steps that
don't first go through `impl Step for Sysroot` (`Rustc` is used for
the `rustc-dev` component).
See https://github.com/rust-lang/rust/pull/79540#discussion_r563350075 and https://github.com/rust-lang/rust/issues/81930 for further context.
Here are some example runs with these changes and `download-rustc`
enabled:
```
$ x.py build src/tools/clippy
Building stage1 tool clippy-driver (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 1m 09s
Building stage1 tool cargo-clippy (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 0.11s
$ x.py test src/tools/clippy
Finished dev [unoptimized + debuginfo] target(s) in 0.09s
Building stage1 tool clippy-driver (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 0.09s
Building rustdoc for stage1 (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 0.28s
Finished release [optimized] target(s) in 15.26s
Running build/x86_64-unknown-linux-gnu/stage1-tools/x86_64-unknown-linux-gnu/release/deps/clippy_driver-
8b407b140e0aa91c
test result: ok. 592 passed; 0 failed; 3 ignored; 0 measured; 0 filtered out
$ x.py build src/tools/rustdoc
Building rustdoc for stage1 (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 41.28s
Build completed successfully in 0:00:41
$ x.py test src/test/rustdoc-ui
Building stage0 tool compiletest (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 0.12s
Building rustdoc for stage1 (x86_64-unknown-linux-gnu)
Finished release [optimized] target(s) in 0.10s
test result: ok. 105 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 8.15s
$ x.py build compiler/rustc
Finished dev [unoptimized + debuginfo] target(s) in 0.09s
Build completed successfully in 0:00:00
```
Note a few things:
- Clippy depends on stage1 rustc-dev artifacts, but rustc didn't have to
be recompiled. Instead, the artifacts were copied automatically.
- All steps are always enabled. There is no danger of forgetting a step,
since only the entrypoints have to handle `download-rustc`.
- Building the compiler (`compiler/rustc`) automatically does no work.
Helps with https://github.com/rust-lang/rust/issues/81930.
r? `@Mark-Simulacrum`
projects / rust.git / commitdiff