Support namespaced error codes

docs/source/error_codes.rst

@@ -38,6 +38,21 @@ thinks is undefined:
    # definition.
    from foolib import foo  # type: ignore[attr-defined]
 
+If you are using multiple type checkers, you can optionally prefix
+mypy-specific error codes with ``mypy:``. By default, mypy ignores unknown
+error codes (as they may be intended for other type checkers). However, error
+codes prefixed with ``mypy:`` will be validated:
+
+.. code-block:: python
+
+   # mypy: warn-unused-ignores
+
+   # Error: Unrecognized error code "attr-undefined"
+   x = 1  # type: ignore[mypy:attr-undefined]
+
+   # OK: error code may be used by other type checker.
+   y = 2  # type: ignore[something-else]
+
 Enabling/disabling specific error codes globally
 ------------------------------------------------
 

mypy/errors.py

@@ -916,7 +916,9 @@ def generate_unused_ignore_errors(self, file: str, is_typeshed: bool = False) ->
             if codes.UNUSED_IGNORE.code in ignored_codes:
                 continue
             used_ignored_codes = set(used_ignored_lines[line])
-            unused_ignored_codes = [c for c in ignored_codes if c not in used_ignored_codes]
+            unused_ignored_codes = [
+                c for c in ignored_codes if c not in used_ignored_codes and c in codes.error_codes
+            ]
             # `ignore` is used
             if not ignored_codes and used_ignored_codes:
                 continue

mypy/nativeparse.py

@@ -46,6 +46,7 @@
     read_str_opt,
     read_tag,
 )
+from mypy.errorcodes import error_codes
 from mypy.errors import CompileError
 from mypy.nodes import (
     ARG_KINDS,
@@ -240,6 +241,8 @@ def native_parse(
         source_hash,
         mypy_comments,
     ) = parse_to_binary_ast(filename, options, source, skip_function_bodies)
+    ignores, extra_errors = normalize_error_codes(ignores)
+    errors.extend(extra_errors)
     node = MypyFile([], [])
     node.path = filename
     node.raw_data = FileRawData(
@@ -255,6 +258,33 @@ def native_parse(
     return node, errors, ignores
 
 
+def normalize_error_codes(ignores: TypeIgnores) -> tuple[TypeIgnores, list[ParseError]]:
+    """Remove mypy: prefix from error codes (if present)."""
+    normalized = []
+    extra_errors: list[ParseError] = []
+    for line, codes in ignores:
+        new_codes = []
+        for c in codes:
+            if not c.startswith("mypy:"):
+                new_codes.append(c)
+                continue
+            c = c.removeprefix("mypy:")
+            if c in error_codes:
+                new_codes.append(c)
+                continue
+            extra_errors.append(
+                {
+                    "line": line,
+                    "column": -1,
+                    "message": f'Unrecognized error code "{c}"',
+                    "blocker": False,
+                    "code": "misc",
+                }
+            )
+        normalized.append((line, new_codes))
+    return normalized, extra_errors
+
+
 def native_parse_type_string(
     expr_string: str, line: int, column: int, end_line: int, end_column: int, options: Options
 ) -> ProperType:

test-data/unit/check-errorcodes.test

@@ -166,15 +166,15 @@ x # type: ignore[name-defined, attr-defined] # E: Unused "type: ignore[attr-defi
 
 [case testErrorCodeWarnUnusedIgnores3]
 # flags: --warn-unused-ignores
-"x".foobar(y) # type: ignore[name-defined, attr-defined, xyz] # E: Unused "type: ignore[xyz]" comment  [unused-ignore]
+"x".foobar(y) # type: ignore[name-defined, attr-defined, xyz]
 
 [case testErrorCodeWarnUnusedIgnores4]
 # flags: --warn-unused-ignores
 "x".foobar(y) # type: ignore[name-defined, attr-defined, valid-type] # E: Unused "type: ignore[valid-type]" comment  [unused-ignore]
 
 [case testErrorCodeWarnUnusedIgnores5]
 # flags: --warn-unused-ignores
-"x".foobar(y) # type: ignore[name-defined, attr-defined, valid-type, xyz] # E: Unused "type: ignore[valid-type, xyz]" comment  [unused-ignore]
+"x".foobar(y) # type: ignore[name-defined, attr-defined, valid-type, xyz] # E: Unused "type: ignore[valid-type]" comment  [unused-ignore]
 
 [case testErrorCodeWarnUnusedIgnores6_NoDetailWhenSingleErrorCode]
 # flags: --warn-unused-ignores

test-data/unit/check-ignore.test

@@ -277,13 +277,13 @@ class CD(six.with_metaclass(M)):  # E: Multiple metaclass definitions
 
 [case testUnusedIgnoreCodeOrder]
 # flags: --warn-unused-ignores
-5 # type: ignore[import, steven] # E: Unused "type: ignore[import, steven]" comment
+5 # type: ignore[import, valid-type] # E: Unused "type: ignore[import, valid-type]" comment
 -- User ordering of codes is preserved
-5 # type: ignore[steven, import] # E: Unused "type: ignore[steven, import]" comment
+5 # type: ignore[valid-type, import] # E: Unused "type: ignore[valid-type, import]" comment
 -- Spacing is not preserved
-5 # type: ignore[  steven,      import ] # E: Unused "type: ignore[steven, import]" comment
+5 # type: ignore[  valid-type,      import ] # E: Unused "type: ignore[valid-type, import]" comment
 -- Make sure it works as intended in more complex situations
-1 + "ok" + "ok".foo # type: ignore[  operator,steven,attr-defined, import] # E: Unused "type: ignore[steven, import]" comment
+1 + "ok" + "ok".foo # type: ignore[  operator,valid-type,attr-defined, import] # E: Unused "type: ignore[valid-type, import]" comment
 
 [case testUnusedIgnoreTryExcept]
 # flags: --warn-unused-ignores
@@ -300,3 +300,12 @@ except Exception:
 [file foobar.py]
 [file barfoo.py]
 [builtins fixtures/exception.pyi]
+
+[case testNamespaceErrorCodes]
+x: str = 42  # type: ignore[mypy:assignment, other:foobar]
+y: str = 42  # type: ignore[mypy:arg-type, other:foobar]
+x = 1  # type: ignore[mypy:foobar]
+[out]
+main:2: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:2: note: Error code "assignment" not covered by "type: ignore[arg-type, other:foobar]" comment
+main:3: error: Unrecognized error code "foobar"