refactor: extract code to open stdin for reading

src/nvim/lua/executor.c

@@ -1724,20 +1724,7 @@ bool nlua_exec_file(const char *path)
     lua_getglobal(lstate, "loadfile");
     lua_pushstring(lstate, path);
   } else {
-    int error;
+    FileDescriptor *stdin_dup = file_open_stdin();
-    int stdin_dup_fd;
-    if (stdin_fd > 0) {
-      stdin_dup_fd = stdin_fd;
-    } else {
-      stdin_dup_fd = os_dup(STDIN_FILENO);
-#ifdef MSWIN
-      // Replace the original stdin with the console input handle.
-      os_replace_stdin_to_conin();
-#endif
-    }
-    FileDescriptor *const stdin_dup = file_open_fd_new(&error, stdin_dup_fd,
-                                                       kFileReadOnly|kFileNonBlocking);
-    assert(stdin_dup != NULL);
 
     StringBuilder sb = KV_INITIAL_VALUE;
     kv_resize(sb, 64);

src/nvim/main.c

@@ -1567,19 +1567,7 @@ static void open_script_files(mparm_T *parmp)
   if (parmp->scriptin) {
     int error;
     if (strequal(parmp->scriptin, "-")) {
-      int stdin_dup_fd;
+      FileDescriptor *stdin_dup = file_open_stdin();
-      if (stdin_fd > 0) {
-        stdin_dup_fd = stdin_fd;
-      } else {
-        stdin_dup_fd = os_dup(STDIN_FILENO);
-#ifdef MSWIN
-        // Replace the original stdin with the console input handle.
-        os_replace_stdin_to_conin();
-#endif
-      }
-      FileDescriptor *const stdin_dup = file_open_fd_new(&error, stdin_dup_fd,
-                                                         kFileReadOnly|kFileNonBlocking);
-      assert(stdin_dup != NULL);
       scriptin[0] = stdin_dup;
     } else {
       scriptin[0] = file_open_new(&error, parmp->scriptin,

src/nvim/os/fileio.c

@@ -167,6 +167,30 @@ FileDescriptor *file_open_fd_new(int *const error, const int fd, const int flags
   return fp;
 }
 
+/// Opens standard input as a FileDescriptor.
+FileDescriptor *file_open_stdin(void)
+  FUNC_ATTR_MALLOC FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  int error;
+  int stdin_dup_fd;
+  if (stdin_fd > 0) {
+    stdin_dup_fd = stdin_fd;
+  } else {
+    stdin_dup_fd = os_dup(STDIN_FILENO);
+#ifdef MSWIN
+    // Replace the original stdin with the console input handle.
+    os_replace_stdin_to_conin();
+#endif
+  }
+  FileDescriptor *const stdin_dup = file_open_fd_new(&error, stdin_dup_fd,
+                                                     kFileReadOnly|kFileNonBlocking);
+  assert(stdin_dup != NULL);
+  if (error != 0) {
+    ELOG("failed to open stdin: %s", os_strerror(error));
+  }
+  return stdin_dup;
+}
+
 /// Close file and free its buffer
 ///
 /// @param[in,out]  fp  File to close.