Proof of concept: gh-64595 fix

Lib/test/test_clinic.py

@@ -72,7 +72,8 @@ def test_eol(self):
  # and since you really already had one,
  # the last line of the block got corrupted.
  raw = "/*[clinic]\nfoo\n[clinic]*/"
- cooked = self.clinic.parse(raw).splitlines()
+ _, cooked = self.clinic.parse(raw)
+ cooked = cooked.splitlines()
  end_line = cooked[2].rstrip()
  # this test is redundant, it's just here explicitly to catch
  # the regression test so we don't forget what it looked like
@@ -131,7 +132,7 @@ def test_parse_with_body_prefix(self):
  //module test
  //[clinic stop]
  """).strip()
- out = cl.parse(raw)
+ _, out = cl.parse(raw)
  expected = dedent("""
  //[clinic start]
  //module test
@@ -198,7 +199,7 @@ def test_directive_output_print(self):
  output print 'I told you once.'
  [clinic start generated code]*/
  """)
- out = self.clinic.parse(raw)
+ _, out = self.clinic.parse(raw)
  # The generated output will differ for every run, but we can check that
  # it starts with the clinic block, we check that it contains all the
  # expected fields, and we check that it contains the checksum line.
@@ -397,7 +398,7 @@ def test_dest_buffer_not_empty_at_eof(self):
  [clinic start generated code]*/
  """)
  with support.captured_stdout() as stdout:
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  self.assertIn(expected_warning, stdout.getvalue())
  self.assertEqual(generated, expected_generated)
 
@@ -435,7 +436,7 @@ def test_directive_set_prefix(self):
  dump buffer
  [clinic start generated code]*/
  """)
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  expected_docstring_prototype = "// PyDoc_VAR(fn__doc__);"
  self.assertIn(expected_docstring_prototype, generated)
 
@@ -455,7 +456,7 @@ def test_directive_set_suffix(self):
  dump buffer
  [clinic start generated code]*/
  """)
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  expected_docstring_prototype = "PyDoc_VAR(fn__doc__); // test"
  self.assertIn(expected_docstring_prototype, generated)
 
@@ -476,7 +477,7 @@ def test_directive_set_prefix_and_suffix(self):
  dump buffer
  [clinic start generated code]*/
  """)
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  expected_docstring_prototype = "/* PyDoc_VAR(fn__doc__); */"
  self.assertIn(expected_docstring_prototype, generated)
 
@@ -495,7 +496,7 @@ def test_directive_printout(self):
  test
  /*[clinic end generated code: output=4e1243bd22c66e76 input=898f1a32965d44ca]*/
  """)
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  self.assertEqual(generated, expected)
 
  def test_directive_preserve_twice(self):
@@ -533,7 +534,7 @@ def test_directive_preserve_output(self):
  [clinic start generated code]*/
  /*[clinic end generated code: output=da39a3ee5e6b4b0d input=524ce2e021e4eba6]*/
  """)
- generated = self.clinic.parse(block)
+ _, generated = self.clinic.parse(block)
  self.assertEqual(generated, block)
 
  def test_directive_output_invalid_command(self):
@@ -813,7 +814,7 @@ def _test_clinic(self, input, output):
  c = clinic.Clinic(language, filename="file", limited_capi=False)
  c.parsers['inert'] = InertParser(c)
  c.parsers['copy'] = CopyParser(c)
- computed = c.parse(input)
+ _, computed = c.parse(input)
  self.assertEqual(output, computed)
 
  def test_clinic_1(self):

Tools/clinic/clinic.py

@@ -2407,6 +2407,7 @@ def parse(self, input: str) -> str:
  header_includes=self.includes)
 
  # these are destinations not buffers
+ generated = []
  for name, destination in self.destinations.items():
  if destination.type == 'suppress':
  continue
@@ -2450,11 +2451,12 @@ def parse(self, input: str) -> str:
  core_includes=True,
  limited_capi=self.limited_capi,
  header_includes=self.includes)
- libclinic.write_file(destination.filename,
-  printer_2.f.getvalue())
+ generated.append((destination.filename,
+ printer_2.f.getvalue()))
  continue
 
- return printer.f.getvalue()
+ cooked = printer.f.getvalue()
+ return generated, cooked
 
  def _module_and_class(
  self, fields: Sequence[str]
@@ -2493,6 +2495,7 @@ def parse_file(
  limited_capi: bool,
  output: str | None = None,
  verify: bool = True,
+ force: bool = False,
 ) -> None:
  if not output:
  output = filename
@@ -2522,9 +2525,14 @@ def parse_file(
  verify=verify,
  filename=filename,
  limited_capi=limited_capi)
- cooked = clinic.parse(raw)
+ generated, cooked = clinic.parse(raw)
 
- libclinic.write_file(output, cooked)
+ changes = [libclinic.file_changed(f, data) for f, data in generated]
+ if any(changes) or libclinic.file_changed(output, cooked) or force:
+ libclinic.write_file(output, cooked)
+ for (output, cooked), changed in zip(generated, changes):
+ if changed or force:
+ libclinic.write_file(output, cooked)
 
 
 class PythonParser:
@@ -6295,7 +6303,8 @@ def run_clinic(parser: argparse.ArgumentParser, ns: argparse.Namespace) -> None:
  if ns.verbose:
  print(path)
  parse_file(path,
- verify=not ns.force, limited_capi=ns.limited_capi)
+ verify=not ns.force, limited_capi=ns.limited_capi,
+ force=ns.force)
  return
 
  if not ns.filename:
@@ -6308,7 +6317,8 @@ def run_clinic(parser: argparse.ArgumentParser, ns: argparse.Namespace) -> None:
  if ns.verbose:
  print(filename)
  parse_file(filename, output=ns.output,
- verify=not ns.force, limited_capi=ns.limited_capi)
+ verify=not ns.force, limited_capi=ns.limited_capi,
+ force=ns.force)
 
 
 def main(argv: list[str] | None = None) -> NoReturn:

Tools/clinic/libclinic/__init__.py

@@ -19,6 +19,7 @@
  FormatCounterFormatter,
  compute_checksum,
  create_regex,
+ file_changed,
  write_file,
 )
 
@@ -43,6 +44,7 @@
  "FormatCounterFormatter",
  "compute_checksum",
  "create_regex",
+ "file_changed",
  "write_file",
 ]
 

Tools/clinic/libclinic/utils.py

@@ -6,17 +6,17 @@
 from typing import Literal
 
 
-def write_file(filename: str, new_contents: str) -> None:
- """Write new content to file, iff the content changed."""
+def file_changed(filename: str, new_contents: str) -> bool:
  try:
  with open(filename, encoding="utf-8") as fp:
  old_contents = fp.read()
 
- if old_contents == new_contents:
- # no change: avoid modifying the file modification time
- return
+ return old_contents != new_contents
  except FileNotFoundError:
- pass
+ return False
+
+
+def write_file(filename: str, new_contents: str) -> None:
  # Atomic write using a temporary file and os.replace()
  filename_new = f"{filename}.new"
  with open(filename_new, "w", encoding="utf-8") as fp: