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Improve error message when a library is not found #158

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merged 4 commits into from Dec 20, 2023

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Finchiedev
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I've noticed that people trying to build a crate which links against a missing library can sometimes be confused by this library's error output. This PR introduces a re-worked error message for that case that focuses on communicating:

  • What's gone wrong?
  • How can I diagnose the cause?
  • What can I do to fix this?

Before (trimmed build.rs output for libsodium-sys-stable):

--- stderr
thread 'main' panicked at build.rs:128:13:
Error: `PKG_CONFIG_ALLOW_SYSTEM_CFLAGS="1" PKG_CONFIG_ALLOW_SYSTEM_LIBS="1" "pkg-config" "--libs" "--cflags" "libsodium"` did not exit successfully: exit status: 1
error: could not find system library 'libsodium' required by the 'libsodium-sys-stable' crate

--- stderr
Package libsodium was not found in the pkg-config search path.
Perhaps you should add the directory containing `libsodium.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libsodium' found

After:

--- stderr
pkg-config exited with status code 1
> PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 pkg-config --libs --cflags libsodium

The system library `libsodium` required by crate `libsodium-sys-stable` was not found.
The file `libsodium.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.
PKG_CONFIG_PATH contains the following:
    - /nix/store/7yx2i1wm89zhypky0l0lmmpl10yf0bh7-openssl-3.0.12-dev/lib/pkgconfig
    - /nix/store/fak09pxs42fqcgngf2yznw83f88kmw7s-zlib-1.3-dev/lib/pkgconfig

HINT: you may need to install a package such as libsodium, libsodium-dev or libsodium-devel.

Thanks to everyone for their invaluable feedback on zulip: https://rust-lang.zulipchat.com/#narrow/stream/351149-t-libs.2Fcrates/topic/More.20helpful.20pkg-config.20output

If there's anything that should be changed please let me know :)

Mostly just small tweaks to existing output, including the following new output:
- Potential packages to install
- Items in PKG_CONFIG_PATH
- Command invocation
@Finchiedev
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Finchiedev commented Dec 17, 2023

Missed some features introduced in 1.57; specifically Command::get_{env, args, program}. Will write a solution and push the fix.

…bles

Before, this was accomplished by using `get_env` and `get_args` manually, but these features are unavailable in 1.30 (current MSRV). To get around this, `Command` is wrapped as `WrappedCommand` and tracks any environment variables or arguments that are set by the caller. Then, the `Display` implementation actually handles pretty-printing the invocation, with the added benefit that other errors can take advantage of this nicer output!
src/lib.rs Outdated
let hint = if let Some(search_path) = search_path {
writeln!(
f,
"PKG_CONFIG_PATH contains the following:\n{}",
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Isn't this confusing for NixOS users? Maybe remember from which variable the search path comes and print that here.

Looks good to me otherwise, thanks a lot :)

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Ah, good catch! Will write a quick fix.

As pointed out by @sdroege in rust-lang#158, Nix users would be misled when
`PKG_CONFIG_PATH_FOR_TARGET` is listed in error output but mistakenly
named `PKG_CONFIG_PATH`.
@Finchiedev
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Apologies for the commit spam, I'm very out of practice using Git! Please let me know if there is anything else I can do.

@sdroege
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sdroege commented Dec 20, 2023

Thanks :)

@sdroege sdroege merged commit 9e485f0 into rust-lang:master Dec 20, 2023
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2 participants