macos: avoid posix_spawnp() cwd bug (#3597)

macOS 10.15 has a bug where configuring the working directory with
posix_spawn_file_actions_addchdir_np() makes posix_spawnp() fail with
ENOENT even though the executable is spawned successfully.

Co-authored-by: Ben Noordhuis <info@bnoordhuis.nl>

src/unix/process.c

@@ -671,27 +671,25 @@ static int uv__spawn_resolve_and_spawn(const uv_process_options_t* options,
   if (options->env != NULL)
     env = options->env;
 
-  /* If options->file contains a slash, posix_spawn/posix_spawnp behave
+  /* If options->file contains a slash, posix_spawn/posix_spawnp should behave
-   * the same, and don't involve PATH resolution at all. Otherwise, if
+   * the same, and do not involve PATH resolution at all. The libc
-   * options->file does not include a slash, but no custom environment is
+   * `posix_spawnp` provided by Apple is buggy (since 10.15), so we now emulate it
-   * to be used, the environment used for path resolution as well for the
+   * here, per https://github.com/libuv/libuv/pull/3583. */
-   * child process is that of the parent process, so posix_spawnp is the
+  if (strchr(options->file, '/') != NULL) {
-   * way to go. */
-  if (strchr(options->file, '/') != NULL || options->env == NULL) {
     do
-      err = posix_spawnp(pid, options->file, actions, attrs, options->args, env);
+      err = posix_spawn(pid, options->file, actions, attrs, options->args, env);
     while (err == EINTR);
     return err;
   }
 
   /* Look for the definition of PATH in the provided env */
-  path = uv__spawn_find_path_in_env(options->env);
+  path = uv__spawn_find_path_in_env(env);
 
   /* The following resolution logic (execvpe emulation) is copied from
    * https://git.musl-libc.org/cgit/musl/tree/src/process/execvp.c
    * and adapted to work for our specific usage */
 
-  /* If no path was provided in options->env, use the default value
+  /* If no path was provided in env, use the default value
    * to look for the executable */
   if (path == NULL)
     path = _PATH_DEFPATH;

test/test-list.h

@@ -321,6 +321,7 @@ TEST_DECLARE   (spawn_inherit_streams)
 TEST_DECLARE   (spawn_quoted_path)
 TEST_DECLARE   (spawn_tcp_server)
 TEST_DECLARE   (spawn_exercise_sigchld_issue)
+TEST_DECLARE   (spawn_relative_path)
 TEST_DECLARE   (fs_poll)
 TEST_DECLARE   (fs_poll_getpath)
 TEST_DECLARE   (fs_poll_close_request)
@@ -956,6 +957,7 @@ TASK_LIST_START
   TEST_ENTRY  (spawn_quoted_path)
   TEST_ENTRY  (spawn_tcp_server)
   TEST_ENTRY  (spawn_exercise_sigchld_issue)
+  TEST_ENTRY  (spawn_relative_path)
   TEST_ENTRY  (fs_poll)
   TEST_ENTRY  (fs_poll_getpath)
   TEST_ENTRY  (fs_poll_close_request)

test/test-spawn.c

@@ -1981,3 +1981,37 @@ void spawn_stdin_stdout(void) {
   }
 }
 #endif /* !_WIN32 */
+
+TEST_IMPL(spawn_relative_path) {
+  char* sep;
+
+  init_process_options("spawn_helper1", exit_cb);
+
+  exepath_size = sizeof(exepath) - 2;
+  ASSERT_EQ(0, uv_exepath(exepath, &exepath_size));
+  exepath[exepath_size] = '\0';
+
+  /* Poor man's basename(3). */
+  sep = strrchr(exepath, '/');
+  if (sep == NULL)
+    sep = strrchr(exepath, '\\');
+  ASSERT_NOT_NULL(sep);
+
+  /* Split into dirname and basename and make basename relative. */
+  memmove(sep + 2, sep, 1 + strlen(sep));
+  sep[0] = '\0';
+  sep[1] = '.';
+  sep[2] = '/';
+
+  options.cwd = exepath;
+  options.file = options.args[0] = sep + 1;
+
+  ASSERT_EQ(0, uv_spawn(uv_default_loop(), &process, &options));
+  ASSERT_EQ(0, uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+
+  ASSERT_EQ(1, exit_cb_called);
+  ASSERT_EQ(1, close_cb_called);
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}