fix(cargo): skip execroot symlink collisions in build script runner

cargo/private/cargo_build_script_runner/bin.rs

@@ -21,7 +21,7 @@ use std::fs::{create_dir_all, read_dir, read_to_string, remove_file, write};
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
-use cargo_build_script_runner::cargo_manifest_dir::{remove_symlink, symlink, RunfilesMaker};
+use cargo_build_script_runner::cargo_manifest_dir::{remove_symlink_if_symlink, symlink, RunfilesMaker};
 use cargo_build_script_runner::{BuildScriptOutput, CompileAndLinkFlags, SUPPRESS_WARNINGS_ENV};
 
 fn run_buildrs() -> Result<(), String> {
@@ -75,10 +75,11 @@ fn run_buildrs() -> Result<(), String> {
                 .ok_or_else(|| "Failed while getting file name".to_string())?;
             let link = manifest_dir.join(file_name);
 
-            symlink_if_not_exists(&path, &link)
-                .map_err(|err| format!("Failed to symlink {path:?} to {link:?}: {err}"))?;
-
-            exec_root_links.push(link)
+            if symlink_if_not_exists(&path, &link)
+                .map_err(|err| format!("Failed to symlink {path:?} to {link:?}: {err}"))?
+            {
+                exec_root_links.push(link);
+            }
         }
     }
 
@@ -237,7 +238,7 @@ fn run_buildrs() -> Result<(), String> {
 
     if !exec_root_links.is_empty() {
         for link in exec_root_links {
-            remove_symlink(&link).map_err(|e| {
+            remove_symlink_if_symlink(&link).map_err(|e| {
                 format!(
                     "Failed to remove exec_root link '{}' with {:?}",
                     link.display(),
@@ -360,9 +361,13 @@ fn set_script_runfiles_env(script_path: &Path, command: &mut Command) {
 }
 
 /// Create a symlink from `link` to `original` if `link` doesn't already exist.
-fn symlink_if_not_exists(original: &Path, link: &Path) -> Result<(), String> {
+fn symlink_if_not_exists(original: &Path, link: &Path) -> Result<bool, String> {
+    if std::fs::symlink_metadata(link).is_ok() {
+        return Ok(false);
+    }
+
     symlink(original, link)
-        .or_else(swallow_already_exists)
+        .map(|_| true)
         .map_err(|err| format!("Failed to create symlink: {err}"))
 }
 
@@ -383,14 +388,6 @@ fn resolve_rundir(rundir: &str, exec_root: &Path, manifest_dir: &Path) -> Result
     Ok(exec_root.join(rundir_path))
 }
 
-fn swallow_already_exists(err: std::io::Error) -> std::io::Result<()> {
-    if err.kind() == std::io::ErrorKind::AlreadyExists {
-        Ok(())
-    } else {
-        Err(err)
-    }
-}
-
 /// A representation of expected command line arguments.
 struct Args {
     progname: String,

cargo/private/cargo_build_script_runner/cargo_manifest_dir.rs

@@ -37,6 +37,16 @@ pub fn remove_symlink(path: &Path) -> Result<(), std::io::Error> {
     }
 }
 
+/// Remove `path` only when it is a symlink.
+pub fn remove_symlink_if_symlink(path: &Path) -> Result<(), std::io::Error> {
+    match std::fs::symlink_metadata(path) {
+        Ok(meta) if meta.file_type().is_symlink() => remove_symlink(path),
+        Ok(_) => Ok(()),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(()),
+        Err(e) => Err(e),
+    }
+}
+
 /// Check if the system supports symlinks by attempting to create one.
 fn system_supports_symlinks(test_dir: &Path) -> Result<bool, String> {
     let test_file = test_dir.join("cbsr.txt");

crate_universe/private/urls.bzl

@@ -6,18 +6,20 @@ the binaries produced for it.
 
 CARGO_BAZEL_URLS = {
     "aarch64-apple-darwin": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-aarch64-apple-darwin",
-    "x86_64-unknown-linux-musl": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-x86_64-unknown-linux-musl",
-    "x86_64-unknown-linux-gnu": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-x86_64-unknown-linux-musl",
-    "aarch64-unknown-linux-musl": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-aarch64-unknown-linux-musl",
     "aarch64-unknown-linux-gnu": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-aarch64-unknown-linux-musl",
+    "aarch64-unknown-linux-musl": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-aarch64-unknown-linux-musl",
+    "x86_64-unknown-linux-gnu": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-x86_64-unknown-linux-musl",
+    "x86_64-unknown-linux-musl": "https://github.com/mgeisler/rules_rust/releases/download/cargo-bazel-prebuilt/cargo-bazel-x86_64-unknown-linux-musl",
 }
 
+
 CARGO_BAZEL_SHA256S = {
     "aarch64-apple-darwin": "5e1617849de558489d2f653644a1ad0c99c4b993fc137f14a7ea890cf06e45d3",
-    "x86_64-unknown-linux-musl": "db72b6ce92031033ffd50d5147ab78d39f5656eb0980bee276d013bc6e3e2260",
-    "x86_64-unknown-linux-gnu": "db72b6ce92031033ffd50d5147ab78d39f5656eb0980bee276d013bc6e3e2260",
-    "aarch64-unknown-linux-musl": "f056c801b59730a2c7cc24fd3606d596d54910068305991b2aa822c32949d4de",
     "aarch64-unknown-linux-gnu": "f056c801b59730a2c7cc24fd3606d596d54910068305991b2aa822c32949d4de",
+    "aarch64-unknown-linux-musl": "f056c801b59730a2c7cc24fd3606d596d54910068305991b2aa822c32949d4de",
+    "x86_64-unknown-linux-gnu": "db72b6ce92031033ffd50d5147ab78d39f5656eb0980bee276d013bc6e3e2260",
+    "x86_64-unknown-linux-musl": "db72b6ce92031033ffd50d5147ab78d39f5656eb0980bee276d013bc6e3e2260",
 }
 
+
 CARGO_BAZEL_LABEL = Label("//crate_universe:cargo_bazel_bin")