Don't canonicalize executable path in cargo_exe (#15355)

### What does this PR try to resolve?

Follow up to #9991. The issue explains why but in short canonicalising
executable paths causes issues for symlinks. It seems this was missed in
#9991.

### How should we test and review this PR?

Note that the comment I deleted is wrong since #9991.

Running existing test should ensure this doesn't break anything.

Author: weihanglo

src/cargo/util/context/mod.rs

@@ -77,7 +77,6 @@ use crate::sources::CRATES_IO_REGISTRY;
 use crate::util::errors::CargoResult;
 use crate::util::network::http::configure_http_handle;
 use crate::util::network::http::http_handle;
-use crate::util::try_canonicalize;
 use crate::util::{internal, CanonicalUrl};
 use crate::util::{Filesystem, IntoUrl, IntoUrlWithBase, Rustc};
 use anyhow::{anyhow, bail, format_err, Context as _};
@@ -457,11 +456,10 @@ impl GlobalContext {
                     // commands that use Cargo as a library to inherit (via `cargo <subcommand>`)
                     // or set (by setting `$CARGO`) a correct path to `cargo` when the current exe
                     // is not actually cargo (e.g., `cargo-*` binaries, Valgrind, `ld.so`, etc.).
-                    let exe = try_canonicalize(
-                        self.get_env_os(crate::CARGO_ENV)
-                            .map(PathBuf::from)
-                            .ok_or_else(|| anyhow!("$CARGO not set"))?,
-                    )?;
+                    let exe = self
+                        .get_env_os(crate::CARGO_ENV)
+                        .map(PathBuf::from)
+                        .ok_or_else(|| anyhow!("$CARGO not set"))?;
                     Ok(exe)
                 };
 
@@ -470,7 +468,7 @@ impl GlobalContext {
                     // The method varies per operating system and might fail; in particular,
                     // it depends on `/proc` being mounted on Linux, and some environments
                     // (like containers or chroots) may not have that available.
-                    let exe = try_canonicalize(env::current_exe()?)?;
+                    let exe = env::current_exe()?;
                     Ok(exe)
                 }
 
@@ -481,8 +479,6 @@ impl GlobalContext {
                     // Otherwise, it has multiple components and is either:
                     // - a relative path (e.g., `./cargo`, `target/debug/cargo`), or
                     // - an absolute path (e.g., `/usr/local/bin/cargo`).
-                    // In either case, `Path::canonicalize` will return the full absolute path
-                    // to the target if it exists.
                     let argv0 = env::args_os()
                         .map(PathBuf::from)
                         .next()

tests/testsuite/build_script.rs

@@ -181,12 +181,9 @@ fn custom_build_env_vars() {
         )
         .file("bar/src/lib.rs", "pub fn hello() {}");
 
-    let cargo = cargo_exe().canonicalize().unwrap();
+    let cargo = cargo_exe();
     let cargo = cargo.to_str().unwrap();
-    let rustc = paths::resolve_executable("rustc".as_ref())
-        .unwrap()
-        .canonicalize()
-        .unwrap();
+    let rustc = paths::resolve_executable("rustc".as_ref()).unwrap();
     let rustc = rustc.to_str().unwrap();
     let file_content = format!(
         r##"

tests/testsuite/cargo_command.rs

@@ -375,7 +375,7 @@ fn cargo_subcommand_env() {
     p.cargo("build").run();
     assert!(p.bin("cargo-envtest").is_file());
 
-    let cargo = cargo_exe().canonicalize().unwrap();
+    let cargo = cargo_exe();
     let mut path = path();
     path.push(target_dir.clone());
     let path = env::join_paths(path.iter()).unwrap();
@@ -388,9 +388,7 @@ fn cargo_subcommand_env() {
     // Check that subcommands inherit an overridden $CARGO
     let envtest_bin = target_dir
         .join("cargo-envtest")
-        .with_extension(std::env::consts::EXE_EXTENSION)
-        .canonicalize()
-        .unwrap();
+        .with_extension(std::env::consts::EXE_EXTENSION);
     let envtest_bin = envtest_bin.to_str().unwrap();
     // Previously, `$CARGO` would be left at `envtest_bin`. However, with the
     // fix for #15099, `$CARGO` is now overwritten with the path to the current
@@ -623,8 +621,6 @@ fn overwrite_cargo_environment_variable() {
     let stderr_cargo = format!(
         "{}[EXE]\n",
         cargo_exe
-            .canonicalize()
-            .unwrap()
             .with_extension("")
             .to_str()
             .unwrap()
@@ -648,8 +644,6 @@ fn overwrite_cargo_environment_variable() {
     let stderr_other_cargo = format!(
         "{}[EXE]\n",
         other_cargo_path
-            .canonicalize()
-            .unwrap()
             .with_extension("")
             .to_str()
             .unwrap()

tests/testsuite/test.rs

@@ -3890,8 +3890,6 @@ fn cargo_test_env() {
     let cargo = format!(
         "{}[EXE]",
         cargo_exe()
-            .canonicalize()
-            .unwrap()
             .with_extension("")
             .to_str()
             .unwrap()
@@ -3913,8 +3911,6 @@ test env_test ... ok
     let stderr_other_cargo = format!(
         "{}[EXE]",
         other_cargo_path
-            .canonicalize()
-            .unwrap()
             .with_extension("")
             .to_str()
             .unwrap()