Auto merge of rust-lang#2909 - osiewicz:rewrite-miri-script-in-rust-2883, r=RalfJung

Rewrite miri script in rust

This is a sketch of a rewrite of miri script in Rust. It does not include changes made in rust-lang/miri#2908 yet. Environment variables are not properly propagated yet, which is something I plan to address.

This PR is mostly a heads-up about the ongoing effort and it's state.
It's definitely not the cleanest code I've seen in my life, but my first goal was feature/interface parity. I will iterate on it a bit before marking it as ready.

I wonder though how this should be integrated/tested. Are you aware of anyone using `./miri` in their scripts?
I guess we should keep existing `miri` script in place and let it run miri-script package directly?

CI should probably `cargo check` this package as well.

Fixes rust-lang#2883

Author: bors

src/tools/miri/.github/workflows/ci.yml

@@ -130,7 +130,7 @@ jobs:
       - name: clippy
         run: ./miri clippy -- -D warnings
       - name: rustdoc
-        run: RUSTDOCFLAGS="-Dwarnings" cargo doc --document-private-items
+        run: RUSTDOCFLAGS="-Dwarnings" ./miri cargo doc --document-private-items
 
   # These jobs doesn't actually test anything, but they're only used to tell
   # bors the build completed, as there is no practical way to detect when a

src/tools/miri/CONTRIBUTING.md

@@ -107,7 +107,7 @@ evaluation error was originally raised.
 ### UI testing
 
 We use ui-testing in Miri, meaning we generate `.stderr` and `.stdout` files for the output
-produced by Miri. You can use `./miri bless` to automatically (re)generate these files when
+produced by Miri. You can use `./miri test --bless` to automatically (re)generate these files when
 you add new tests or change how Miri presents certain output.
 
 Note that when you also use `MIRIFLAGS` to change optimizations and similar, the ui output

src/tools/miri/cargo-miri/src/phases.rs

@@ -538,8 +538,7 @@ pub fn phase_runner(mut binary_args: impl Iterator<Item = String>, phase: Runner
     }
     // Respect `MIRIFLAGS`.
     if let Ok(a) = env::var("MIRIFLAGS") {
-        // This code is taken from `RUSTFLAGS` handling in cargo.
-        let args = a.split(' ').map(str::trim).filter(|s| !s.is_empty()).map(str::to_string);
+        let args = flagsplit(&a);
         cmd.args(args);
     }
 

src/tools/miri/cargo-miri/src/util.rs

@@ -114,6 +114,11 @@ pub fn cargo() -> Command {
     Command::new(env::var_os("CARGO").unwrap_or_else(|| OsString::from("cargo")))
 }
 
+pub fn flagsplit(flags: &str) -> Vec<String> {
+    // This code is taken from `RUSTFLAGS` handling in cargo.
+    flags.split(' ').map(str::trim).filter(|s| !s.is_empty()).map(str::to_string).collect()
+}
+
 /// Execute the `Command`, where possible by replacing the current process with a new process
 /// described by the `Command`. Then exit this process with the exit code of the new process.
 pub fn exec(mut cmd: Command) -> ! {