[empath-split] Fix --preserve-manifest option (#25637)

`--preserve-manifest` was doing the opposite of what it meant to do:
deleting the manifest file when `--preserve-manifest` was given and not
deleting it when it was not given.

But simply changing
```py
with tempfile.NamedTemporaryFile(suffix=".manifest", mode='w+', delete=args.preserve_manifest) as f:
```
```py
with tempfile.NamedTemporaryFile(suffix=".manifest", mode='w+', delete=not args.preserve_manifest) as f:
```
doesn't work, because of Windows' peculiar behavior.

It looks in Windows it is not allowed to re-open an already opened file
unless some conditions are met:
https://docs.python.org/3/library/tempfile.html
> Opening the temporary file again by its name while it is still open
works as follows:
> - On POSIX the file can always be opened again.
> - On Windows, make sure that at least one of the following conditions
are fulfilled:
>   - `delete` is false
> - additional open shares delete access (e.g. by calling
[os.open()](https://docs.python.org/3/library/os.html#os.open) with the
flag `O_TEMPORARY`)
> - `delete` is true but `delete_on_close` is false. Note, that in this
case the additional opens that do not share delete access (e.g. created
via builtin
[open()](https://docs.python.org/3/library/functions.html#open)) must be
closed before exiting the context manager, else the
[os.unlink()](https://docs.python.org/3/library/os.html#os.unlink) call
on context manager exit will fail with a
[PermissionError](https://docs.python.org/3/library/exceptions.html#PermissionError).

And we are trying to reopen a temporary file within the `with` context.
The Windows CI didn't error out before this PR because the first
condition (`delete` is false) was accidentally satisfied due to this
bug. To fix this I think we can't help but use `try`-`finally`.

Author: aheejin

test/test_other.py

@@ -15183,7 +15183,8 @@ def test_empath_split(self):
     ''')
 
     self.run_process([EMCC, 'main.cpp', 'foo.cpp', '-gsource-map', '-g2', '-o', 'test.js'])
-    self.run_process([empath_split, 'test.wasm', 'path_list.txt', '-g', '-o', 'test_primary.wasm', '--out-prefix=test_'])
+    empath_split_cmd = [empath_split, 'test.wasm', 'path_list.txt', '-g', '-o', 'test_primary.wasm', '--out-prefix=test_', '-v']
+    out = self.run_process(empath_split_cmd, stdout=PIPE).stdout
 
     # Check if functions are correctly assigned and split with the specified
     # paths. When one path contains another, the inner path should take its
@@ -15207,6 +15208,18 @@ def has_defined_function(file, func):
     self.assertTrue(has_defined_function('test_lib2.wasm', r'std::__2::ios_base::getloc\\28\\29\\20const'))
     self.assertTrue(has_defined_function('test_lib2.wasm', r'std::uncaught_exceptions\\28\\29'))
 
+    # When --preserve-manifest is NOT given, the files should be deleted
+    match = re.search(r'wasm-split(?:\.exe)?\s+.*--manifest\s+(\S+)', out)
+    manifest = match.group(1)
+    self.assertNotExists(manifest)
+
+    # When --preserve-manifest is given, the files should be preserved
+    out = self.run_process(empath_split_cmd + ['--preserve-manifest'], stdout=PIPE, stderr=subprocess.DEVNULL).stdout
+    match = re.search(r'wasm-split(?:\.exe)?\s+.*--manifest\s+(\S+)', out)
+    manifest = match.group(1)
+    self.assertExists(manifest)
+    delete_file(manifest)
+
     # Check --print-sources option
     out = self.run_process([empath_split, 'test.wasm', '--print-sources'], stdout=PIPE).stdout
     self.assertIn('main.cpp', out)

tools/empath-split.py

@@ -314,8 +314,9 @@ def main():
   path_to_funcs = get_path_to_functions_map(args.wasm, sourcemap, all_paths)
 
   # Write .manifest file
-  with tempfile.NamedTemporaryFile(suffix=".manifest", mode='w+', delete=args.preserve_manifest) as f:
-    manifest = f.name
+  f = tempfile.NamedTemporaryFile(suffix=".manifest", mode='w+', delete=False)
+  manifest = f.name
+  try:
     for i, (module, paths) in enumerate(module_to_paths.items()):
       if i != 0: # Unless we are the first entry add a newline separator
         f.write('\n')
@@ -339,7 +340,7 @@ def main():
       f.write(f'{module}\n')
       for func in funcs:
         f.write(func + '\n')
-    f.flush()
+    f.close()
 
     cmd = [args.wasm_split, '--multi-split', args.wasm, '--manifest', manifest]
     if args.verbose:
@@ -349,6 +350,9 @@ def main():
     if args.verbose:
       print('\n' + ' '.join(cmd))
     shared.run_process(cmd)
+  finally:
+    if not args.preserve_manifest:
+      os.remove(manifest)
 
 
 if __name__ == '__main__':