Type ignore comments erroneously marked as unused by dmypy

mypy/dmypy_server.py

@@ -684,10 +684,11 @@ def refresh_file(module: str, path: str) -> list[str]:
 
  # Find all original modules in graph that were not reached -- they are deleted.
  to_delete = []
+ seen_and_ancestors = self._seen_and_ancestors(seen)
  for module_id in orig_modules:
  if module_id not in graph:
  continue
- if module_id not in seen:
+ if module_id not in seen_and_ancestors:
  module_path = graph[module_id].path
  assert module_path is not None
  to_delete.append((module_id, module_path))
@@ -715,6 +716,29 @@ def refresh_file(module: str, path: str) -> list[str]:
 
  return messages
 
+ def _seen_and_ancestors(self, seen: set[str]) -> set[str]:
+ """Return the set of seen modules along with any ancestors not already in the set.
+
+ For example, given this set:
+
+ {"foo", "foo.bar", "a.b.c"}
+
+ ... we would expect this set to be returned:
+
+ {"foo", "foo.bar", "a.b.c", "a.b", "a"}
+
+ This is used to stop us from deleting ancestor modules from the graph
+ when their descendants have been seen.
+ """
+ seen_paths = seen.copy()
+ for module_path in seen:
+ while module_path := module_path.rpartition(".")[0]:
+ if module_path in seen_paths:
+ break
+ else:
+ seen_paths.add(module_path)
+ return seen_paths
+
  def find_reachable_changed_modules(
  self,
  roots: list[BuildSource],

mypy/errors.py

@@ -725,6 +725,8 @@ def generate_unused_ignore_errors(self, file: str) -> None:
  blocker=False,
  only_once=False,
  allow_dups=False,
+ origin=(self.file, [line]),
+ target=self.target_module,
  )
  self._add_error_info(file, info)
 
@@ -777,6 +779,8 @@ def generate_ignore_without_code_errors(
  blocker=False,
  only_once=False,
  allow_dups=False,
+ origin=(self.file, [line]),
+ target=self.target_module,
  )
  self._add_error_info(file, info)
 

mypy/server/update.py

@@ -667,6 +667,8 @@ def restore(ids: list[str]) -> None:
  state.type_check_first_pass()
  state.type_check_second_pass()
  state.detect_possibly_undefined_vars()
+ state.generate_unused_ignore_notes()
+ state.generate_ignore_without_code_notes()
  t2 = time.time()
  state.finish_passes()
  t3 = time.time()

test-data/unit/daemon.test

@@ -615,3 +615,140 @@ b: str
 from demo.test import a
 [file demo/test.py]
 a: int
+
+[case testUnusedTypeIgnorePreservedOnRerun]
+-- Regression test for https:/python/mypy/issues/9655
+$ dmypy start -- --warn-unused-ignores --no-error-summary --hide-error-codes
+Daemon started
+$ dmypy check -- bar.py
+bar.py:2: error: Unused "type: ignore" comment
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:2: error: Unused "type: ignore" comment
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+a = 1 # type: ignore
+
+[case testTypeIgnoreWithoutCodePreservedOnRerun]
+-- Regression test for https:/python/mypy/issues/9655
+$ dmypy start -- --enable-error-code ignore-without-code --no-error-summary
+Daemon started
+$ dmypy check -- bar.py
+bar.py:2: error: "type: ignore" comment without error code [ignore-without-code]
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:2: error: "type: ignore" comment without error code [ignore-without-code]
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+a = 1 # type: ignore
+
+[case testPossiblyUndefinedVarsPreservedAfterRerun]
+-- Regression test for https:/python/mypy/issues/9655
+$ dmypy start -- --enable-error-code possibly-undefined --no-error-summary
+Daemon started
+$ dmypy check -- bar.py
+bar.py:4: error: Name "a" may be undefined [possibly-undefined]
+== Return code: 1
+$ dmypy check -- bar.py
+bar.py:4: error: Name "a" may be undefined [possibly-undefined]
+== Return code: 1
+
+[file foo/__init__.py]
+[file foo/empty.py]
+[file bar.py]
+from foo.empty import *
+if False:
+ a = 1
+a
+
+[case testUnusedTypeIgnorePreservedOnRerunWithIgnoredMissingImports]
+$ dmypy start -- --no-error-summary --ignore-missing-imports --warn-unused-ignores
+Daemon started
+$ dmypy check foo
+foo/main.py:3: error: Unused "type: ignore" comment [unused-ignore]
+== Return code: 1
+$ dmypy check foo
+foo/main.py:3: error: Unused "type: ignore" comment [unused-ignore]
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/submodule.py]
+[file foo/empty.py]
+[file foo/__init__.py]
+from foo.main import *
+from unused.submodule import *
+[file foo/main.py]
+from foo import empty
+from foo.does_not_exist import *
+a = 1 # type: ignore
+
+[case testModuleDoesNotExistPreservedOnRerun]
+$ dmypy start -- --no-error-summary --ignore-missing-imports
+Daemon started
+$ dmypy check foo
+foo/main.py:1: error: Module "foo" has no attribute "does_not_exist" [attr-defined]
+== Return code: 1
+$ dmypy check foo
+foo/main.py:1: error: Module "foo" has no attribute "does_not_exist" [attr-defined]
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/submodule.py]
+[file foo/__init__.py]
+from foo.main import *
+[file foo/main.py]
+from foo import does_not_exist
+from unused.submodule import *
+
+[case testReturnTypeIgnoreAfterUnknownImport]
+-- Return type ignores after unknown imports and unused modules are respected on the second pass.
+$ dmypy start -- --warn-unused-ignores --no-error-summary
+Daemon started
+$ dmypy check -- foo.py
+foo.py:2: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist" [import-not-found]
+foo.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+$ dmypy check -- foo.py
+foo.py:2: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist" [import-not-found]
+foo.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/empty.py]
+[file foo.py]
+from unused.empty import *
+import a_module_which_does_not_exist
+def is_foo() -> str:
+ return True # type: ignore
+
+[case testAttrsTypeIgnoreAfterUnknownImport]
+$ dmypy start -- --warn-unused-ignores --no-error-summary
+Daemon started
+$ dmypy check -- foo.py
+foo.py:3: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist" [import-not-found]
+foo.py:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+$ dmypy check -- foo.py
+foo.py:3: error: Cannot find implementation or library stub for module named "a_module_which_does_not_exist" [import-not-found]
+foo.py:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+== Return code: 1
+
+[file unused/__init__.py]
+[file unused/empty.py]
+[file foo.py]
+import attr
+from unused.empty import *
+import a_module_which_does_not_exist
+
+@attr.frozen
+class A:
+ def __init__(self) -> None:
+ self.__attrs_init__() # type: ignore[attr-defined]

test-data/unit/fine-grained.test

@@ -10505,3 +10505,27 @@ from pkg.sub import modb
 
 [out]
 ==
+
+[case testUnusedTypeIgnorePreservedAfterChange]
+# flags: --warn-unused-ignores --no-error-summary
+[file main.py]
+a = 1 # type: ignore
+[file main.py.2]
+a = 1 # type: ignore
+# Comment to trigger reload.
+[out]
+main.py:1: error: Unused "type: ignore" comment
+==
+main.py:1: error: Unused "type: ignore" comment
+
+[case testTypeIgnoreWithoutCodePreservedAfterChange]
+# flags: --enable-error-code ignore-without-code --no-error-summary
+[file main.py]
+a = 1 # type: ignore
+[file main.py.2]
+a = 1 # type: ignore
+# Comment to trigger reload.
+[out]
+main.py:1: error: "type: ignore" comment without error code
+==
+main.py:1: error: "type: ignore" comment without error code