Add basic implementation for mypy: ignore comments

docs/source/error_codes.rst

@@ -53,6 +53,43 @@ codes prefixed with ``mypy:`` will be validated:
    # OK: error code may be used by other type checker.
    y = 2  # type: ignore[something-else]
 
+An alternative way to specify mypy-specific type ignores is to use
+``# mypy: ignore[one-code, other-code]``. Such form is equivalent to writing
+``# type: ignore[mypy:one-code, mypy:other-code]``. You can have both
+``# type: ignore[...]`` and ``# mypy: ignore[...]`` on the same line, in this
+case the error code lists will be merged.
+
+Note that to allow better interoperability with other tools, mypy recognizes
+``# type: ignore`` and ``mypy: ignore`` in any position in a comment, including
+after another "magic" comments used by other tools. To temporarily disable
+an ignore, place it after an empty (i.e. whitespace only) comment. For example:
+
+.. code-block:: python
+
+   from typing import Any
+
+   # No error, type ignore is active.
+   x: str = 1  # noqa  # pragma: no cover  # type: ignore[assignment]
+
+   # Error: Incompatible types in assignment (expression has type "int", variable has type "str")
+   y: str = 1  ## type: ignore[assignment]
+
+   # Error: Incompatible types in assignment (expression has type "int", variable has type "str")
+   z: str = 1  # # type: ignore[assignment]
+
+The only exception to this logic, is if there is no other code on a line
+except for the comment. In this case type ignores preceded by another comment
+are disabled. This is done to avoid spurious errors about unused ignores in
+a commented out block of code:
+
+.. code-block:: python
+
+   # mypy: warn-unused-ignores
+
+   x: int = 1
+   # OK, no unused-ignore error below.
+   # x = "no way"  # type: ignore[assignment]
+
 Enabling/disabling specific error codes globally
 ------------------------------------------------
 

mypy/nativeparse.py

@@ -235,14 +235,25 @@ def native_parse(
         b,
         errors,
         ignores,
+        mypy_ignores,
         import_bytes,
         is_partial_package,
         uses_template_strings,
         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)
+    mypy_ignores, extra_errors = normalize_error_codes(
+        mypy_ignores, verify_all=True, prohibit_prefix=True
+    )
+    errors.extend(extra_errors)
+
+    ignores = merge_type_ignores(ignores, mypy_ignores)
+    ignores, extra_errors = remove_duplicate_codes(ignores)
+    errors.extend(extra_errors)
+
     node = MypyFile([], [])
     node.path = filename
     node.raw_data = FileRawData(
@@ -258,29 +269,89 @@ def native_parse(
     return node, errors, ignores
 
 
-def normalize_error_codes(ignores: TypeIgnores) -> tuple[TypeIgnores, list[ParseError]]:
+def normalize_error_codes(
+    ignores: TypeIgnores, verify_all: bool = False, prohibit_prefix: bool = False
+) -> 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
+            prefixed = c.startswith("mypy:")
             c = c.removeprefix("mypy:")
-            if c in error_codes:
-                new_codes.append(c)
+            # Always record unknown codes, so that type: ignore[unknown]
+            # will not become blanket ignore.
+            new_codes.append(c)
+            if (prefixed or verify_all) and c not in error_codes:
+                extra_errors.append(
+                    {
+                        "line": line,
+                        "column": -1,
+                        "message": f'Unrecognized error code "{c}"',
+                        "blocker": False,
+                        "code": "misc",
+                    }
+                )
+            if prefixed and prohibit_prefix:
+                extra_errors.append(
+                    {
+                        "line": line,
+                        "column": -1,
+                        "message": 'Error codes in "mypy: ignore" should not be prefixed',
+                        "blocker": False,
+                        "code": "misc",
+                    }
+                )
+        normalized.append((line, new_codes))
+    return normalized, extra_errors
+
+
+def merge_type_ignores(ignores: TypeIgnores, mypy_ignores: TypeIgnores) -> TypeIgnores:
+    """Merge error codes specified in # type: ignore[...] and in # mypy: ignore[...]."""
+    merged = []
+    ignores_by_line = dict(ignores)
+    mypy_ignores_by_line = dict(mypy_ignores)
+    for line in sorted(ignores_by_line.keys() | mypy_ignores_by_line.keys()):
+        codes = ignores_by_line.get(line)
+        mypy_codes = mypy_ignores_by_line.get(line)
+        if codes is not None and mypy_codes is None:
+            new_codes = codes
+        elif codes is None and mypy_codes is not None:
+            new_codes = mypy_codes
+        else:
+            assert codes is not None and mypy_codes is not None
+            if not codes or not mypy_codes:
+                # If at least one ignore is blanket, make the merged ignore blanket.
+                # We are not overly strict here, in case someone wants to quickly
+                # silence everything.
+                new_codes = []
+            else:
+                new_codes = codes + mypy_codes
+        merged.append((line, new_codes))
+    return merged
+
+
+def remove_duplicate_codes(ignores: TypeIgnores) -> tuple[TypeIgnores, list[ParseError]]:
+    normalized = []
+    extra_errors: list[ParseError] = []
+    for line, codes in ignores:
+        seen = set()
+        new_codes = []
+        for c in codes:
+            if c in seen:
+                extra_errors.append(
+                    {
+                        "line": line,
+                        "column": -1,
+                        "message": f'Duplicate error code "{c}"',
+                        "blocker": False,
+                        "code": "misc",
+                    }
+                )
                 continue
-            extra_errors.append(
-                {
-                    "line": line,
-                    "column": -1,
-                    "message": f'Unrecognized error code "{c}"',
-                    "blocker": False,
-                    "code": "misc",
-                }
-            )
+            seen.add(c)
+            new_codes.append(c)
         normalized.append((line, new_codes))
     return normalized, extra_errors
 
@@ -327,7 +398,17 @@ def parse_to_binary_ast(
     options: Options,
     source: str | bytes | None = None,
     skip_function_bodies: bool = False,
-) -> tuple[bytes, list[ParseError], TypeIgnores, bytes, bool, bool, str, list[tuple[int, str]]]:
+) -> tuple[
+    bytes,
+    list[ParseError],
+    TypeIgnores,
+    TypeIgnores,
+    bytes,
+    bool,
+    bool,
+    str,
+    list[tuple[int, str]],
+]:
     try:
         ast_bytes, errors, ignores, import_bytes, ast_data = ast_serialize.parse(
             filename,
@@ -337,7 +418,7 @@ def parse_to_binary_ast(
             platform=options.platform,
             always_true=options.always_true,
             always_false=options.always_false,
-            cache_version=5,
+            cache_version=7,
         )
     except ValueError as exc:
         if source is None:
@@ -366,6 +447,7 @@ def parse_to_binary_ast(
         ast_bytes,
         errors,
         ignores,
+        ast_data["mypy_ignores"],
         import_bytes,
         ast_data["is_partial_package"],
         ast_data["uses_template_strings"],
@@ -796,6 +878,7 @@ def read_func_def(state: State, data: ReadBuffer) -> FuncDef:
     func_def = FuncDef(name, arguments, body, typ=typ, type_args=type_params)
     if is_async:
         func_def.is_coroutine = True
+    func_def.has_type_comments = read_bool(data)
     read_loc(data, func_def)
     if type_params:
         state.check_min_version(

mypy/nodes.py

@@ -1114,6 +1114,7 @@ class FuncDef(FuncItem, SymbolNode, Statement):
         "docstring",
         "deprecated",
         "original_first_arg",
+        "has_type_comments",
     )
 
     __match_args__ = ("name", "arguments", "type", "body")
@@ -1156,6 +1157,9 @@ def __init__(
         # We record this status to avoid multiple (similar but different) errors in case
         # of partial types etc.
         self.is_invalid_redefinition = False
+        # Record if the function definition has any type comments (including per-argument).
+        # This is only available with the native parser (and always False otherwise).
+        self.has_type_comments = False
 
     @property
     def name(self) -> str:

mypy/parse.py

@@ -95,6 +95,7 @@ def load_from_raw(
     # Report parse errors, this replicates the logic in parse().
     all_errors = raw_data.raw_errors + state.errors
     errors.set_file(fnam, module, options=options)
+    errors.set_file_ignored_lines(fnam, tree.ignored_lines, options.ignore_errors)
     for error in all_errors:
         # Note we never raise in this function, so it should not be called in coordinator.
         report_parse_error(error, errors)

mypy/test/test_nativeparse.py

@@ -268,15 +268,15 @@ def locs(start_line: int, start_column: int, end_line: int, end_column: int) ->
 
     def test_trivial_binary_data_from_file(self) -> None:
         with temp_source("print('hello')") as fnam:
-            b, _, _, _, _, _, _, _ = parse_to_binary_ast(fnam, Options())
+            b, _, _, _, _, _, _, _, _ = parse_to_binary_ast(fnam, Options())
             self._assert_trivial_binary_data(b)
 
     def test_trivial_binary_data_from_string_source(self) -> None:
-        b, _, _, _, _, _, _, _ = parse_to_binary_ast("", Options(), "print('hello')")
+        b, _, _, _, _, _, _, _, _ = parse_to_binary_ast("", Options(), "print('hello')")
         self._assert_trivial_binary_data(b)
 
     def test_trivial_binary_data_from_bytes_source(self) -> None:
-        b, _, _, _, _, _, _, _ = parse_to_binary_ast("", Options(), b"print('hello')")
+        b, _, _, _, _, _, _, _, _ = parse_to_binary_ast("", Options(), b"print('hello')")
         self._assert_trivial_binary_data(b)
 
     def test_invalid_bytes_raises(self) -> None:

test-data/unit/check-deprecated.test

@@ -49,7 +49,7 @@ from typing_extensions import deprecated
 @deprecated("use f2 instead")
 def f() -> None: ...
 
-f  # E: function __main__.f is deprecated: use f2 instead  # type: ignore[deprecated]
+f  # E: function __main__.f is deprecated: use f2 instead
 f(1)  # E: function __main__.f is deprecated: use f2 instead \
       # E: Too many arguments for "f"
 f[1]  # E: function __main__.f is deprecated: use f2 instead \

test-data/unit/check-fastparse.test

@@ -77,7 +77,8 @@ for i in (1, 2, 3, 100):  # type: str # type: ignore
     pass
 [builtins fixtures/tuple.pyi]
 
-[case testFastParseVariableCommentThenIgnore]
+-- New parser has a different stance on this.
+[case testFastParseVariableCommentThenIgnore_old_parser]
 a="test" # type: int #comment # type: ignore  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
 
 [case testFastParseProperty]

test-data/unit/check-ignore.test

@@ -309,3 +309,96 @@ x = 1  # type: ignore[mypy:foobar]
 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"
+main:3: note: Error code "misc" not covered by "type: ignore[foobar]" comment
+main:3: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:3: note: Error code "assignment" not covered by "type: ignore[foobar]" comment
+
+[case testIgnoreNonBlockingParseError]
+# flags: --python-version=3.10
+m[*(), :]  # type: ignore[syntax]
+[builtins fixtures/tuple.pyi]
+[out]
+main:2: error: Name "m" is not defined
+main:2: note: Error code "name-defined" not covered by "type: ignore[syntax]" comment
+
+[case testIgnoreNonBlockingParseErrorSilent]
+# cmd: mypy -m a
+# flags: --python-version=3.10 --follow-import=silent
+[file a.py]
+import m
+reveal_type(m.x)  # N: Revealed type is "builtins.int"
+[file m.py]
+x: int
+x = m[*(), :]
+[builtins fixtures/tuple.pyi]
+[out]
+
+[case testIgnoresWorkAfterOtherComments]
+x: str = 1  # noqa  # pragma: no cover  # type: ignore
+y: str = 1  # noqa  # pragma: no cover  # mypy: ignore
+z: str = 1  # noqa  # pragma: no cover  # type: ignore[assignment]
+t: str = 1  # noqa  # pragma: no cover  # mypy: ignore[assignment]
+
+x1: str = 1  ## type: ignore
+y1: str = 1  ## mypy: ignore
+z1: str = 1  ## type: ignore[assignment]
+t1: str = 1  ## mypy: ignore[assignment]
+
+x2: str = 1  # noqa  ## type: ignore
+y2: str = 1  # noqa  ## mypy: ignore
+z2: str = 1  # noqa  ## type: ignore[assignment]
+t2: str = 1  # noqa  ## mypy: ignore[assignment]
+[out]
+main:6: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:7: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:8: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:9: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:11: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:12: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:13: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:14: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+
+[case testPrefixInMypyCommentNotAllowed]
+x: str = 1  # mypy: ignore[mypy:assignment]
+[out]
+main:1: error: Error codes in "mypy: ignore" should not be prefixed
+main:1: note: Error code "misc" not covered by "type: ignore[assignment]" comment
+
+[case testDuplicateErrorCodeNotAllowed]
+x: str = 1  # mypy: ignore[assignment]  # type: ignore[assignment]
+[out]
+main:1: error: Duplicate error code "assignment"
+main:1: note: Error code "misc" not covered by "type: ignore[assignment]" comment
+
+[case testUnusedMypyIgnoreReported]
+# flags: --warn-unused-ignores
+x = 1  # mypy: ignore
+y = 1  # mypy: ignore[assignment]
+z: str = 1  # mypy: ignore[assignment, arg-type]
+[out]
+main:2: error: Unused "type: ignore" comment
+main:3: error: Unused "type: ignore" comment
+main:4: error: Unused "type: ignore[arg-type]" comment
+
+[case testNoUnusedIgnoreInCommentedBlock]
+# flags: --warn-unused-ignores
+# x: str = 1  # mypy: ignore
+# y: str = 1  # type: ignore
+# z: str = 1  # mypy: ignore[assignment]
+# t: str = 1  # type: ignore[assignment]
+
+[case testIgnoreErrorCodesMerged]
+def f() -> None: pass
+
+f(x)  # mypy: ignore[name-defined]  # type: ignore[call-arg]
+f(x)  # type: ignore[name-defined]  # mypy: ignore[call-arg]
+
+[case testBlanketIgnoreWinsWhenMixed]
+x  # mypy: ignore  # type: ignore[assignment]
+y  # mypy: ignore[assignment]  # type: ignore
+
+[case testUnknownErrorCodeNotAllowedInMypyIgnore]
+1  # mypy: ignore[whatever]
+[out]
+main:1: error: Unrecognized error code "whatever"
+main:1: note: Error code "misc" not covered by "type: ignore[whatever]" comment