handle errors in rename better

Author: kripken

src/library_fs.js

@@ -676,6 +676,7 @@ mergeInto(LibraryManager.library, {
       } catch (e) {
         throw new FS.ErrnoError(ERRNO_CODES.EBUSY);
       }
+      if (!old_dir || !new_dir) throw new FS.ErrnoError(ERRNO_CODES.ENOENT);
       // need to be part of the same mount
       if (old_dir.mount !== new_dir.mount) {
         throw new FS.ErrnoError(ERRNO_CODES.EXDEV);

tests/test_other.py

@@ -3050,6 +3050,27 @@ def test_symlink_silly(self):
     self.assertContained(r'''ok''', run_js('a.out.js', args=['123', 'abc']))
     self.assertContained(r'''Failed to symlink paths: abc, ; errno=2''', run_js('a.out.js', args=['abc', '']))
 
+  def test_rename_silly(self):
+    open('src.cpp', 'w').write(r'''
+#include <stdio.h>
+#include <errno.h>
+
+int main(int argc, char **argv) {
+  if (rename(argv[1], argv[2]) != 0) {
+    printf("Failed to rename paths: %s, %s; errno=%d\n", argv[1], argv[2], errno);
+  } else {
+    printf("ok\n");
+  }
+}
+    ''')
+    Popen([PYTHON, EMCC, 'src.cpp']).communicate()
+
+    # cannot symlink nonexistents
+    self.assertContained(r'''Failed to rename paths: , abc; errno=2''', run_js('a.out.js', args=['', 'abc']))
+    self.assertContained(r'''Failed to rename paths: , ; errno=2''', run_js('a.out.js', args=['', '']))
+    self.assertContained(r'''Failed to rename paths: 123, abc; errno=2''', run_js('a.out.js', args=['123', 'abc']))
+    self.assertContained(r'''Failed to rename paths: abc, ; errno=2''', run_js('a.out.js', args=['abc', '']))
+
   def test_emversion(self):
     open('src.cpp', 'w').write(r'''
       #include <stdio.h>