fn discover_rlib_deps()

in src/compiler/rust.rs [2492:2552]

• 52 lines of code
• 5 McCabe index (conditional complexity)

    fn discover_rlib_deps(
        &self,
        env_vars: &[(OsString, OsString)],
        rlib: &Path,
    ) -> Result<Vec<String>> {
        let rlib_mtime = fs::metadata(rlib)
            .and_then(|m| m.modified())
            .context("Unable to get rlib modified time")?;

        {
            let mut cache = self.cache.lock().unwrap();
            if let Some(deps_detail) = cache.get(rlib) {
                if rlib_mtime == deps_detail.mtime {
                    return Ok(deps_detail.deps.clone());
                }
            }
        }

        trace!("Discovering dependencies of {}", rlib.display());

        let mut cmd = process::Command::new(&self.executable);
        cmd.args(["-Z", &self.ls_arg])
            .arg(rlib)
            .env_clear()
            .envs(env_vars.to_vec())
            .env("RUSTC_BOOTSTRAP", "1"); // TODO: this is fairly naughty

        let process::Output {
            status,
            stdout,
            stderr,
        } = cmd.output()?;

        if !status.success() {
            bail!(format!("Failed to list deps of {}", rlib.display()))
        }
        if !stderr.is_empty() {
            bail!(
                "rustc -Z ls stderr non-empty: {:?}",
                String::from_utf8_lossy(&stderr)
            )
        }

        let stdout = String::from_utf8(stdout).context("Error parsing rustc -Z ls output")?;
        let deps: Vec<_> = parse_rustc_z_ls(&stdout)
            .map(|deps| deps.into_iter().map(|dep| dep.to_owned()).collect())?;

        {
            // This will behave poorly if the rlib is changing under our feet, but in that case rustc
            // will also do the wrong thing, so the user has bigger issues to deal with.
            let mut cache = self.cache.lock().unwrap();
            cache.insert(
                rlib.to_owned(),
                RlibDepsDetail {
                    deps: deps.clone(),
                    mtime: rlib_mtime,
                },
            );
        }
        Ok(deps)
    }