Build script failure hidden by dependency build failure

[huonw]

# a/Cargo.toml
[package]

name = "a"
version = "0.0.1"
authors = []
build = "build.rs"

[dependencies.b]
path = "../b"

// a/build.rs
fn main() { std::os::set_exit_status(1) }

# b/Cargo.toml
[package]

name = "b"
version = "0.0.1"
authors = []

// b/src/lib.rs
invalid

Then in a:

cargo clean && cargo build 
   Compiling a v0.0.1 (file:///home/huon/projects/test-rust/tmp/a)
   Compiling b v0.0.1 (file:///home/huon/projects/test-rust/tmp/a)
/home/huon/projects/test-rust/tmp/b/src/lib.rs:1:1: 1:8 error: expected item, found `invalid`
/home/huon/projects/test-rust/tmp/b/src/lib.rs:1 invalid
                                                 ^~~~~~~
Build failed, waiting for other jobs to finish...
Could not compile `b`.

The user is probably certainly more interested in the build script failing to build/run than the dependency. @alexcrichton's suggested resolution of #832 would possibly resolve this automatically too.

[alexcrichton]

This is actually ordering-dependent and relies on the fact that we capture build script output rather than printing it by default.

We probably shouldn't discard all extra output though.

[marti1125]

@alexcrichton is It still open? I would like to contribute

[alexcrichton]

@marti1125 I think this may have actually been fixed in the meantime, but if you'd like to add a test for this that'd be most welcome!

[marti1125]

@alexcrichton could you tell me more about the test please =D

[alexcrichton]

Sure yeah, all of Cargo's tests live in tests/*.rs in this repository, and you'd probably just extend tests/build.rs for this. You can copy/paste from previous examples but the general idea is that a Cargo project is created and then you run cargo build, placing assertions on the output of Cargo and the exit status of the process.

[dwijnand]

I think this may have actually been fixed in the meantime

I think it hasn't, sadly.

It's also slightly bit-rot: I changed a/build.rs to the following instead:

fn main() { panic!("boom!"); }

The new output is fundamentally the same:

$ cargo clean && cargo build
   Compiling b v0.0.1 (file:///s/t-build-script-failure/b)
   Compiling a v0.0.1 (file:///s/t-build-script-failure/a)
error: expected one of `!` or `::`, found `<eof>`
 --> /s/t-build-script-failure/b/src/lib.rs:1:1
  |
1 | invalid
  | ^^^^^^^ expected one of `!` or `::` here

error: aborting due to previous error

error: Could not compile `b`.
warning: build failed, waiting for other jobs to finish...
error: build failed

How should the other failures be reported? With handle_error?

[alexcrichton]

@dwijnand in your reproduction are you sure that the build script executed? It may be that the build script was only compiled, not run, in that example

[dwijnand]

Given build.rs:

fn main() {
    use std::fs::File;
    use std::io::prelude::*;

    let mut file = File::create("marker.txt").unwrap();
    file.write_all(b"Hi Alex!").unwrap();

    panic!("boom!");
}

Looks like it doesn't even run the build script!

17:40:35 $ cargo clean && cargo build
   Compiling a v0.0.1 (file:///s/t-build-script-failure/a)
   Compiling b v0.0.1 (file:///s/t-build-script-failure/b)
error: expected one of `!` or `::`, found `<eof>`
 --> /s/t-build-script-failure/b/src/lib.rs:1:1
  |
1 | invalid
  | ^^^^^^^ expected one of `!` or `::` here

error: aborting due to previous error

error: Could not compile `b`.
warning: build failed, waiting for other jobs to finish...
error: build failed

17:40:54 ! cat marker.txt
cat: marker.txt: No such file or directory

in that example

Am I not accurately reproducing the reported issue? Maybe I've misunderstood some part of it.

[alexcrichton]

@dwijnand oh if you execute cargo build -v you can see:

   Compiling b v0.1.0 (file:///home/alex/code/cargo-vendor/a/b)
   Compiling a v0.1.0 (file:///home/alex/code/cargo-vendor/a)
     Running `rustc --crate-name b b/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=159cd516bfae43d6 -C extra-filename=-159cd516bfae43d6 --out-dir /home/alex/code/cargo-vendor/a/target/debug/deps -C incremental=/home/alex/code/cargo-vendor/a/target/debug/incremental -L dependency=/home/alex/code/cargo-vendor/a/target/debug/deps`
     Running `rustc --crate-name build_script_build build.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=9c9757b7d885b49f -C extra-filename=-9c9757b7d885b49f --out-dir /home/alex/code/cargo-vendor/a/target/debug/build/a-9c9757b7d885b49f -C incremental=/home/alex/code/cargo-vendor/a/target/debug/incremental -L dependency=/home/alex/code/cargo-vendor/a/target/debug/deps`
error: expected one of `!` or `::`, found `<eof>`
 --> b/src/lib.rs:1:1
  |
1 | ix
  | ^^ expected one of `!` or `::` here

error: aborting due to previous error

error: Could not compile `b`.

Caused by:
  process didn't exit successfully: `rustc --crate-name b b/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=159cd516bfae43d6 -C extra-filename=-159cd516bfae43d6 --out-dir /home/alex/code/cargo-vendor/a/target/debug/deps -C incremental=/home/alex/code/cargo-vendor/a/target/debug/incremental -L dependency=/home/alex/code/cargo-vendor/a/target/debug/deps` (exit code: 101)
warning: build failed, waiting for other jobs to finish...
error: build failed

where the build script wasn't even executed here, it was just compiled

[dwijnand]

So where does this leave this issue?

I thought the whole premise is that the build script failure should be output. But if it doesn't even run..

[alexcrichton]

@dwijnand oh I think this has since been basically fixed, although it may not be easily testable. Cargo will stop running commands as soon as one fails, which is why you're not seeing the build script output