Use open() to write the bytecode

And drop the related tests, because we can't test partial writes any
more. But, we're now relying on well-tested code.

Author: stefanor

Lib/importlib/_bootstrap_external.py

@@ -208,8 +208,8 @@ def _write_atomic(path, data, mode=0o666):
     try:
         # We first write data to a temporary file, and then use os.replace() to
         # perform an atomic rename.
-        with _io.FileIO(fd, 'wb') as file, _io.BufferedWriter(file) as writer:
-            writer.write(data)
+        with open(fd, 'wb') as file:
+            file.write(data)
         _os.replace(path_tmp, path)
     except OSError:
         try:

Lib/test/test_importlib/test_util.py

@@ -6,7 +6,6 @@
 importlib_util = util.import_importlib('importlib.util')
 
 import importlib.util
-from importlib import _bootstrap_external
 import os
 import pathlib
 import string
@@ -788,74 +787,5 @@ def test_complete_multi_phase_init_module(self):
             self.run_with_own_gil(script)
 
 
-class PatchAtomicWrites():
-    def __init__(self, truncate_at_length=100, never_complete=False):
-        self.truncate_at_length = truncate_at_length
-        self.never_complete = never_complete
-        self.seen_write = False
-        self._children = []
-
-    def __enter__(self):
-        import _pyio
-
-        oldwrite = os.write
-
-        # Emulate an os.write that only writes partial data.
-        def write(fd, data):
-            if self.seen_write and self.never_complete:
-                return None
-            self.seen_write = True
-            return oldwrite(fd, data[:self.truncate_at_length])
-
-        # Need to patch _io to be _pyio, so that io.FileIO is affected by the
-        # os.write patch.
-        self.children = [
-            support.swap_attr(_bootstrap_external, '_io', _pyio),
-            support.swap_attr(os, 'write', write)
-        ]
-        for child in self.children:
-            child.__enter__()
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        for child in self.children:
-            child.__exit__(exc_type, exc_val, exc_tb)
-
-
-class MiscTests(unittest.TestCase):
-
-    def test_atomic_write_retries_incomplete_writes(self):
-        truncate_at_length = 100
-        length = truncate_at_length * 2
-
-        with PatchAtomicWrites(truncate_at_length=truncate_at_length) as cm:
-            # Make sure we write something longer than the point where we
-            # truncate.
-            content = b'x' * length
-            _bootstrap_external._write_atomic(os_helper.TESTFN, content)
-        assert cm.seen_write
-
-        assert os.stat(support.os_helper.TESTFN).st_size == length
-        os.unlink(support.os_helper.TESTFN)
-
-    def test_atomic_write_errors_if_unable_to_complete(self):
-        truncate_at_length = 100
-
-        with (
-            PatchAtomicWrites(
-                truncate_at_length=truncate_at_length, never_complete=True,
-            ) as cm,
-            self.assertRaises(OSError)
-        ):
-            # Make sure we write something longer than the point where we
-            # truncate.
-            content = b'x' * (truncate_at_length * 2)
-            _bootstrap_external._write_atomic(os_helper.TESTFN, content)
-        assert cm.seen_write
-
-        with self.assertRaises(OSError):
-            os.stat(support.os_helper.TESTFN) # Check that the file did not get written.
-
-
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2025-11-24-21-09-30.gh-issue-141930.hIIzSd.rst

@@ -1 +1 @@
-Use ``BufferedWriter`` to ensure that writes to ``.pyc`` files are retried, or an appropriate error is raised.
+Use Python's regular file object to ensure that writes to ``.pyc`` files are retried, or an appropriate error is raised.