Auto merge of #11944 - workingjubilee:env-lookup-for-cargo, r=Jarcho

Check $CARGO before $PATH

Currently, clippy will ignore $CARGO when spawning cargo commands, which can be problematic for `cargo clippy` and interop with other tools. This commit induces clippy to respect $CARGO in every case it seems likely to matter.

Fixes:
- #11943

changelog: clippy now respects setting the `CARGO` environment variable

clippy_dev/src/lint.rs

@@ -1,6 +1,6 @@
 use crate::{cargo_clippy_path, exit_if_err};
-use std::fs;
 use std::process::{self, Command};
+use std::{env, fs};
 
 pub fn run<'a>(path: &str, args: impl Iterator<Item = &'a String>) {
     let is_file = match fs::metadata(path) {
@@ -13,7 +13,7 @@ pub fn run<'a>(path: &str, args: impl Iterator<Item = &'a String>) {
 
     if is_file {
         exit_if_err(
-            Command::new("cargo")
+            Command::new(env::var("CARGO").unwrap_or("cargo".into()))
                 .args(["run", "--bin", "clippy-driver", "--"])
                 .args(["-L", "./target/debug"])
                 .args(["-Z", "no-codegen"])
@@ -23,7 +23,11 @@ pub fn run<'a>(path: &str, args: impl Iterator<Item = &'a String>) {
                 .status(),
         );
     } else {
-        exit_if_err(Command::new("cargo").arg("build").status());
+        exit_if_err(
+            Command::new(env::var("CARGO").unwrap_or("cargo".into()))
+                .arg("build")
+                .status(),
+        );
 
         let status = Command::new(cargo_clippy_path())
             .arg("clippy")

clippy_dev/src/serve.rs

@@ -2,8 +2,8 @@
 use std::num::ParseIntError;
 use std::path::Path;
 use std::process::Command;
-use std::thread;
 use std::time::{Duration, SystemTime};
+use std::{env, thread};
 
 /// # Panics
 ///
@@ -16,7 +16,7 @@ pub fn run(port: u16, lint: Option<&String>) -> ! {
 
     loop {
         if mtime("util/gh-pages/lints.json") < mtime("clippy_lints/src") {
-            Command::new("cargo")
+            Command::new(env::var("CARGO").unwrap_or("cargo".into()))
                 .arg("collect-metadata")
                 .spawn()
                 .unwrap()

clippy_lints/src/utils/internal_lints/metadata_collector.rs

@@ -28,12 +28,12 @@
 use serde::ser::SerializeStruct;
 use serde::{Serialize, Serializer};
 use std::collections::{BTreeSet, BinaryHeap};
-use std::fmt;
 use std::fmt::Write as _;
 use std::fs::{self, File};
 use std::io::prelude::*;
 use std::path::{Path, PathBuf};
 use std::process::Command;
+use std::{env, fmt};
 
 /// This is the json output file of the lint collector.
 const JSON_OUTPUT_FILE: &str = "../util/gh-pages/lints.json";
@@ -415,7 +415,7 @@ fn get_lint_output(lint_name: &str, example: &[&mut String], clippy_project_root
 
     let prefixed_name = format!("{CLIPPY_LINT_GROUP_PREFIX}{lint_name}");
 
-    let mut cmd = Command::new("cargo");
+    let mut cmd = Command::new(env::var("CARGO").unwrap_or("cargo".into()));
 
     cmd.current_dir(clippy_project_root)
         .env("CARGO_INCREMENTAL", "0")

lintcheck/src/main.rs

@@ -367,7 +367,7 @@ fn run_clippy_lints(
             //
             // The wrapper is set to the `lintcheck` so we can force enable linting and ignore certain crates
             // (see `crate::driver`)
-            let status = Command::new("cargo")
+            let status = Command::new(env::var("CARGO").unwrap_or("cargo".into()))
                 .arg("check")
                 .arg("--quiet")
                 .current_dir(&self.path)
@@ -441,7 +441,7 @@ fn run_clippy_lints(
 
 /// Builds clippy inside the repo to make sure we have a clippy executable we can use.
 fn build_clippy() {
-    let status = Command::new("cargo")
+    let status = Command::new(env::var("CARGO").unwrap_or("cargo".into()))
         .arg("build")
         .status()
         .expect("Failed to build clippy!");
@@ -816,7 +816,7 @@ fn lintcheck_test() {
         "--crates-toml",
         "lintcheck/test_sources.toml",
     ];
-    let status = std::process::Command::new("cargo")
+    let status = std::process::Command::new(env::var("CARGO").unwrap_or("cargo".into()))
         .args(args)
         .current_dir("..") // repo root
         .status();

src/main.rs

@@ -105,7 +105,7 @@ fn path() -> PathBuf {
     }
 
     fn into_std_cmd(self) -> Command {
-        let mut cmd = Command::new("cargo");
+        let mut cmd = Command::new(env::var("CARGO").unwrap_or("cargo".into()));
         let clippy_args: String = self
             .clippy_args
             .iter()