Use CARGO env variable if present (#453)

* Run `$CARGO -vV` in `detect-targets` if env `CARGO` present
* Improve crate doc for `detect-targets`
* Use env var `CARGO` in `install_from_source` if present
* Test use of `CARGO` env in `tests.sh`

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

.github/scripts/tests.sh

@@ -3,17 +3,25 @@
 set -euxo pipefail
 
 unset CARGO_INSTALL_ROOT
-unset CARGO_HOME
 
-# Install binaries using cargo-binstall
-# shellcheck disable=SC2086
-"./$1" binstall --log-level debug --no-confirm \
-    b3sum \
-    cargo-release \
-    cargo-binstall \
-    cargo-watch \
-    miniserve \
-    sccache
+crates="b3sum cargo-release cargo-binstall cargo-watch miniserve sccache"
+
+if [ "$2" = "Windows" ]; then
+    # Install binaries using cargo-binstall
+    # shellcheck disable=SC2086
+    "./$1" --log-level debug --no-confirm $crates
+else
+    export CARGO_HOME=/tmp/cargo-home-for-test
+    export PATH="$CARGO_HOME/bin:$PATH"
+    
+    mkdir -p "$CARGO_HOME/bin"
+    # Copy it to bin to test use of env var `CARGO`
+    cp "./$1" "$CARGO_HOME/bin/cargo-binstall"
+    
+    # Install binaries using cargo-binstall
+    # shellcheck disable=SC2086
+    cargo binstall --log-level debug --no-confirm $crates
+fi
 
 # Test that the installed binaries can be run
 b3sum --version
@@ -69,7 +77,7 @@ cargo binstall --help >/dev/null
 
 # to force failure if falling back to source
 # FIXME: remove/replace once #136 lands
-PATH="$test_resources/fake-cargo:$PATH"
+export PATH="$test_resources/fake-cargo:$PATH"
 
 # Test default GitLab pkg-url templates
 "./$1" binstall \

.github/workflows/integration.yml

@@ -51,6 +51,4 @@ jobs:
     - name: Test
       shell: bash
       run: .github/scripts/tests.sh ${{ matrix.bin }} ${{ runner.os }}
-      env:
-        CARGO_HOME: /tmp/cargo-home-for-test/
 

crates/binstalk/src/ops/install.rs

@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use std::{borrow::Cow, env, ffi::OsStr, sync::Arc};
 
 use cargo_toml::Package;
 use compact_str::CompactString;
@@ -110,12 +110,18 @@ async fn install_from_source(
 ) -> Result<(), BinstallError> {
     let jobserver_client = lazy_jobserver_client.get().await?;
 
+    let cargo = env::var_os("CARGO")
+        .map(Cow::Owned)
+        .unwrap_or_else(|| Cow::Borrowed(OsStr::new("cargo")));
+
     debug!(
-        "Running `cargo install {} --version {} --target {target}`",
-        package.name, package.version
+        "Running `{} install {} --version {} --target {target}`",
+        cargo.to_string_lossy(),
+        package.name,
+        package.version
     );
 
-    let mut cmd = Command::new("cargo");
+    let mut cmd = Command::new(cargo);
 
     cmd.arg("install")
         .arg(&package.name)

crates/detect-targets/src/detect.rs

@@ -1,4 +1,7 @@
 use std::{
+    borrow::Cow,
+    env,
+    ffi::OsStr,
     io::{BufRead, Cursor},
     process::{Output, Stdio},
 };
@@ -65,8 +68,17 @@ pub async fn detect_targets() -> Vec<String> {
 
 /// Figure out what the host target is using `rustc`.
 /// If `rustc` is absent, then it would return `None`.
+///
+/// If environment variable `CARGO` is present, then
+/// `$CARGO -vV` will be run instead.
+///
+/// Otherwise, it will run `rustc -vV` to detect target.
 async fn get_target_from_rustc() -> Option<String> {
-    let Output { status, stdout, .. } = Command::new("rustc")
+    let cmd = env::var_os("CARGO")
+        .map(Cow::Owned)
+        .unwrap_or_else(|| Cow::Borrowed(OsStr::new("rustc")));
+
+    let Output { status, stdout, .. } = Command::new(cmd)
         .arg("-vV")
         .stdin(Stdio::null())
         .stdout(Stdio::piped())

crates/detect-targets/src/lib.rs

@@ -1,5 +1,11 @@
 //! Detect the target at the runtime.
 //!
+//! It runs `$CARGO -vV` if environment variable `CARGO` is present
+//! for cargo subcommands, otherwise it would try running `rustc -vV`.
+//!
+//! If both `rustc` isn't present on the system, it will fallback
+//! to using syscalls plus `ldd` on Linux to detect targets.
+//!
 //! Example use cases:
 //!  - The binary is built with musl libc to run on anywhere, but
 //!    the runtime supports glibc.