Building tests with gn

[Tim Kilbourn]

When I build a rust_library that sets with_tests = true, I don't see full error messages from the compiler. Is there a way to get those errors printed during a gn build? Or some equivalent Cargo commandline I can use?

[1/12] ACTION //rust/mxio:mxio(//build/toolchain/fuchsia:x64)

FAILED: obj/rust/mxio/mxio.rust/x86_64-unknown-fuchsia/release/libmxio.rmeta gen/rust/mxio/mxio.rust/mxio.info.toml obj/rust/mxio/mxio.rust/mxio-lib-test 

/usr/bin/env ../../build/rust/build_target.py --type lib --name mxio --out-dir /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64/obj/rust/mxio/mxio.rust --gen-dir /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64/gen/rust/mxio/mxio.rust --root-out-dir /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64 --root-gen-dir /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64/gen --crate-root /usr/local/google/home/tkilbourn/src/fuchsia/rust/mxio --cargo /usr/local/google/home/tkilbourn/src/fuchsia/buildtools/rust/rust-x86_64-unknown-linux-gnu/bin/cargo --rustc /usr/local/google/home/tkilbourn/src/fuchsia/buildtools/rust/rust-x86_64-unknown-linux-gnu/bin/rustc --target-triple x86_64-unknown-fuchsia --label //rust/mxio:mxio --cmake-dir /usr/local/google/home/tkilbourn/src/fuchsia/buildtools/cmake/bin --vendor-directory /usr/local/google/home/tkilbourn/src/fuchsia/third_party/rust-crates/vendor --deps //rust/magenta-rs:magenta //rust/magenta-rs/magenta-sys:magenta-sys //third_party/rust-crates:tempdir-0.3.5 --shared-libs-root /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64/x64-shared --with-tests --release --linker /usr/local/google/home/tkilbourn/src/fuchsia/out/release-x86-64/host_x64/x86_64-unknown-fuchsia-cc

error: Could not compile `mxio`.

To learn more, run the command again with --verbose.

Traceback (most recent call last):

  File "../../build/rust/build_target.py", line 351, in <module>

    sys.exit(main())

  File "../../build/rust/build_target.py", line 332, in main

    messages = subprocess.check_output(test_args, env=env, cwd=args.gen_dir)

  File "/usr/lib/python2.7/subprocess.py", line 573, in check_output

    raise CalledProcessError(retcode, cmd, output=output)

subprocess.CalledProcessError: Command '['/usr/local/google/home/tkilbourn/src/fuchsia/buildtools/rust/rust-x86_64-unknown-linux-gnu/bin/cargo', 'test', '--target=x86_64-unknown-fuchsia', '-q', '--release', '--lib', '--no-run', '--message-format=json']' returned non-zero exit status 101

ninja: build stopped: subcommand failed.

[Tim Kilbourn]

Rob pointed me at Fargo which can build the tests to show the compilation errors. With cargo, it's as easy as checking out fargo and running 'cargo install'. Then set $FUCHSIA_ROOT (bug filed to find it automatically if you're in a Fuchsia checkout) and run 'fargo build-tests' in the crate's dir. Now I just have to figure out how to get our package system to put a library's tests into user.bootfs.