cli: add show-env subcommand

[davidhewitt]

Implements the show-env suggestion from #93 (comment)

An example output:

$ cargo llvm-cov show-env
RUSTFLAGS=" -Z instrument-coverage --remap-path-prefix /home/david/dev/pyo3/= --cfg coverage --cfg trybuild_no_target"
LLVM_PROFILE_FILE="/home/david/dev/pyo3/target/llvm-cov-target/pyo3-%m.profraw"
CARGO_INCREMENTAL="0"
CARGO_TARGET_DIR="/home/david/dev/pyo3/target/llvm-cov-target"

After exporting these vars, I had a go at building pyo3's cdylib examples and then running them with pytest.

Pleased to see that I do get profile output in the expected location:

$ ls target/llvm-cov-target/
CACHEDIR.TAG                         pyo3-6622988374613674511_0.profraw
debug                                pyo3-8390305564713967804_0.profraw
pyo3-10144924340354712083_0.profraw  pyo3-8655209440434687052_0.profraw
pyo3-12448306348928428713_0.profraw  pyo3-9115749969700858718_0.profraw
pyo3-13212718739740305352_0.profraw  pyo3-9296542518232051450_0.profraw
pyo3-17208771140764127027_0.profraw  pyo3.profdata
pyo3-40338836728015828_0.profraw     release
pyo3-5761173678925874245_0.profraw   wheels
pyo3-6135639819960792837_0.profraw

There's still some pain points:

1. I need to unset CARGO_TARGET_DIR before attempting to run cargo llvm-cov command, or I get crashes because it tries to append llvm-cov-target for a second time:

$ cargo llvm-cov --no-run --summary-only
error: no input files specified. See llvm-profdata merge -help
error: failed to merge profile data: process didn't exit successfully: `/home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-profdata merge -sparse -o /home/david/dev/pyo3/target/llvm-cov-target/llvm-cov-target/pyo3.profdata` (exit status: 1)

2. After unsetting CARGO_TARGET_DIR, I still get a failure to generate the report. I suspect this is because cargo-llvm-cov is not finding and passing the cdylib outputs to llvm-cov report?

$ cargo llvm-cov --no-run --summary-only --verbose
   Running `/home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-profdata merge -sparse /home/david/dev/pyo3/target/llvm-cov-target/pyo3-10144924340354712083_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-12448306348928428713_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-13212718739740305352_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-17208771140764127027_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-40338836728015828_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-5761173678925874245_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-6135639819960792837_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-6622988374613674511_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-8390305564713967804_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-8655209440434687052_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-9115749969700858718_0.profraw /home/david/dev/pyo3/target/llvm-cov-target/pyo3-9296542518232051450_0.profraw -o /home/david/dev/pyo3/target/llvm-cov-target/pyo3.profdata`
   Running `/home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-cov report -instr-profile=/home/david/dev/pyo3/target/llvm-cov-target/pyo3.profdata -ignore-filename-regex '(^|/)(rustc/[0-9a-f]+|(\.)?cargo/(registry|git)|(\.)?rustup/toolchains|tests|examples|benches|target/llvm-cov-target)/|^/home/david/|^pyo3-macros/|^pyo3-macros-backend/|^pyo3-build-config/|^examples/|^xtask/'`
No filenames specified!
error: failed to generate report: process didn't exit successfully: `/home/david/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/llvm-cov report -instr-profile=/home/david/dev/pyo3/target/llvm-cov-target/pyo3.profdata -ignore-filename-regex '(^|/)(rustc/[0-9a-f]+|(\.)?cargo/(registry|git)|(\.)?rustup/toolchains|tests|examples|benches|target/llvm-cov-target)/|^/home/david/|^pyo3-macros/|^pyo3-macros-backend/|^pyo3-build-config/|^examples/|^xtask/'` (exit status: 1)

If you're interested, you can see the companion PyO3 at PyO3/pyo3#2067

[taiki-e]

Thanks!

I need to unset CARGO_TARGET_DIR before attempting to run cargo llvm-cov command

We are going to remove this environment variable in #112. Perhaps that will fix this problem?

After unsetting CARGO_TARGET_DIR, I still get a failure to generate the report. I suspect this is because cargo-llvm-cov is not finding and passing the cdylib outputs to llvm-cov report?

Hmm... I'll take a look later.

[davidhewitt]

We are going to remove this environment variable in #112. Perhaps that will fix this problem?

Yep, rebasing has fixed that, nice 👍

It may be useful to have an option to output environment variables with the export prefix.

Added. Note you can use this one-liner even:

source <(cargo llvm-cov show-env --export-prefix)

[davidhewitt]

Pushed some tidy and test fixes, and added a short note to the README based on the comment in #93.

[taiki-e]

LGTM

[taiki-e]

bors r+

[bors]

Build succeeded!

And happy new year! 🎉

• ci

[davidhewitt]

Thanks, sorry for the slow review turnaround, have been busy over the festive season!

[taiki-e]

Published in 0.1.14.

sorry for the slow review turnaround

No problem. (The only reason I applied the changes myself was to avoid conflicts with a subsequent huge patch.)

[taiki-e]

2. After unsetting CARGO_TARGET_DIR, I still get a failure to generate the report. I suspect this is because cargo-llvm-cov is not finding and passing the cdylib outputs to llvm-cov report?

IIUC, the problem is that cargo-llvm-cov and cargo refer to different build artists, so I guess it will work if passing --target-dir target/llvm-cov-target to cargo build.

[davidhewitt]

IIUC, the problem is that cargo-llvm-cov and cargo refer to different build artists, so I guess it will work if passing --target-dir target/llvm-cov-target to cargo build.

Turns out it was partly this and also that for various reasons some of the build output was going into the release dir instead of debug. I have nearly got a working implementation with cargo llvm-cov show-env at PyO3/pyo3#2105

Thanks again!