Add regression test when unable to run compiler in doctest

Author: GuillaumeGomez

src/librustdoc/doctest.rs

@@ -501,10 +501,7 @@ fn add_exe_suffix(input: String, target: &TargetTuple) -> String {
     input + &exe_suffix
 }
 
-fn wrapped_rustc_command<'a>(
-    rustc_wrappers: &'a [PathBuf],
-    rustc_binary: &'a Path,
-) -> (Command, &'a Path) {
+fn wrapped_rustc_command<'a>(rustc_wrappers: &'a [PathBuf], rustc_binary: &'a Path) -> Command {
     let mut args = rustc_wrappers.iter().map(PathBuf::as_path).chain([rustc_binary]);
 
     let exe = args.next().expect("unable to create rustc command");
@@ -513,7 +510,7 @@ fn wrapped_rustc_command<'a>(
         command.arg(arg);
     }
 
-    (command, rustc_wrappers.first().map(|p| &**p).unwrap_or(rustc_binary))
+    command
 }
 
 /// Information needed for running a bundle of doctests.
@@ -633,8 +630,7 @@ fn run_test(
         .test_builder
         .as_deref()
         .unwrap_or_else(|| rustc_interface::util::rustc_path(sysroot).expect("found rustc"));
-    let (mut compiler, binary_path) =
-        wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
+    let mut compiler = wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
 
     compiler.args(&compiler_args);
 
@@ -675,6 +671,7 @@ fn run_test(
 
     debug!("compiler invocation for doctest: {compiler:?}");
 
+    let binary_path = compiler.get_program().to_os_string();
     let mut child = match compiler.spawn() {
         Ok(child) => child,
         Err(error) => {
@@ -690,7 +687,7 @@ fn run_test(
         // build it now
         let runner_input_file = doctest.path_for_merged_doctest_runner();
 
-        let (mut runner_compiler, binary_path) =
+        let mut runner_compiler =
             wrapped_rustc_command(&rustdoc_options.test_builder_wrappers, rustc_binary);
         // the test runner does not contain any user-written code, so this doesn't allow
         // the user to exploit nightly-only features on stable
@@ -743,6 +740,7 @@ fn run_test(
         let status = if !status.success() {
             status
         } else {
+            let binary_path = runner_compiler.get_program().to_os_string();
             let mut child_runner = match runner_compiler.spawn() {
                 Ok(child) => child,
                 Err(error) => {

tests/run-make/rustdoc-test-builder/foo.rs

@@ -0,0 +1,3 @@
+//! ```
+//! let x = 12;
+//! ```

tests/run-make/rustdoc-test-builder/rmake.rs

@@ -0,0 +1,22 @@
+// This test ensures that if the rustdoc test binary is not executable, it will
+// gracefully fail and not panic.
+
+//@ needs-target-std
+
+use run_make_support::{path, rfs, rustdoc};
+
+fn main() {
+    let absolute_path = path("foo.rs").canonicalize().expect("failed to get absolute path");
+    let output = rustdoc()
+        .input("foo.rs")
+        .arg("--test")
+        .arg("-Zunstable-options")
+        .arg("--test-builder")
+        .arg(&absolute_path)
+        .run_fail();
+
+    output.assert_stdout_contains("Failed to spawn ");
+    output.assert_stderr_not_contains("the compiler unexpectedly panicked. this is a bug.");
+    // Just in case...
+    output.assert_stdout_not_contains("the compiler unexpectedly panicked. this is a bug.");
+}