[mypyc] fix: reject invalid mypyc_attr args [1/1] (#19963)

This PR emits a builder error when an invalid key is passed into
`mypyc_attr`. This change could have saved me ~20 minutes or so, when
the root of my problem was just a simple typo.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: BobTheBuidler

mypyc/irbuild/prepare.py

@@ -357,7 +357,7 @@ def prepare_class_def(
     ir = mapper.type_to_ir[cdef.info]
     info = cdef.info
 
-    attrs, attrs_lines = get_mypyc_attrs(cdef)
+    attrs, attrs_lines = get_mypyc_attrs(cdef, path, errors)
     if attrs.get("allow_interpreted_subclasses") is True:
         ir.allow_interpreted_subclasses = True
     if attrs.get("serializable") is True:

mypyc/irbuild/util.py

@@ -2,7 +2,8 @@
 
 from __future__ import annotations
 
-from typing import Any
+from typing import Any, Final, Literal, TypedDict, cast
+from typing_extensions import NotRequired
 
 from mypy.nodes import (
     ARG_NAMED,
@@ -31,7 +32,23 @@
 from mypy.types import FINAL_DECORATOR_NAMES
 from mypyc.errors import Errors
 
-DATACLASS_DECORATORS = {"dataclasses.dataclass", "attr.s", "attr.attrs"}
+MYPYC_ATTRS: Final[frozenset[MypycAttr]] = frozenset(
+    ["native_class", "allow_interpreted_subclasses", "serializable", "free_list_len"]
+)
+
+DATACLASS_DECORATORS: Final = frozenset(["dataclasses.dataclass", "attr.s", "attr.attrs"])
+
+
+MypycAttr = Literal[
+    "native_class", "allow_interpreted_subclasses", "serializable", "free_list_len"
+]
+
+
+class MypycAttrs(TypedDict):
+    native_class: NotRequired[bool]
+    allow_interpreted_subclasses: NotRequired[bool]
+    serializable: NotRequired[bool]
+    free_list_len: NotRequired[int]
 
 
 def is_final_decorator(d: Expression) -> bool:
@@ -112,21 +129,39 @@ def get_mypyc_attr_call(d: Expression) -> CallExpr | None:
     return None
 
 
-def get_mypyc_attrs(stmt: ClassDef | Decorator) -> tuple[dict[str, Any], dict[str, int]]:
+def get_mypyc_attrs(
+    stmt: ClassDef | Decorator, path: str, errors: Errors
+) -> tuple[MypycAttrs, dict[MypycAttr, int]]:
     """Collect all the mypyc_attr attributes on a class definition or a function."""
-    attrs: dict[str, Any] = {}
-    lines: dict[str, int] = {}
+    attrs: MypycAttrs = {}
+    lines: dict[MypycAttr, int] = {}
+
+    def set_mypyc_attr(key: str, value: Any, line: int) -> None:
+        if key in MYPYC_ATTRS:
+            key = cast(MypycAttr, key)
+            attrs[key] = value
+            lines[key] = line
+        else:
+            errors.error(f'"{key}" is not a supported "mypyc_attr"', path, line)
+            supported_keys = '", "'.join(sorted(MYPYC_ATTRS))
+            errors.note(f'supported keys: "{supported_keys}"', path, line)
+
     for dec in stmt.decorators:
-        d = get_mypyc_attr_call(dec)
-        if d:
+        if d := get_mypyc_attr_call(dec):
+            line = d.line
             for name, arg in zip(d.arg_names, d.args):
                 if name is None:
                     if isinstance(arg, StrExpr):
-                        attrs[arg.value] = True
-                        lines[arg.value] = d.line
+                        set_mypyc_attr(arg.value, True, line)
+                    else:
+                        errors.error(
+                            'All "mypyc_attr" positional arguments must be string literals.',
+                            path,
+                            line,
+                        )
                 else:
-                    attrs[name] = get_mypyc_attr_literal(arg)
-                    lines[name] = d.line
+                    arg_value = get_mypyc_attr_literal(arg)
+                    set_mypyc_attr(name, arg_value, line)
 
     return attrs, lines
 

mypyc/test-data/irbuild-classes.test

@@ -2837,3 +2837,18 @@ L0:
     r6 = PyObject_VectorcallMethod(r3, r5, 9223372036854775812, 0)
     keep_alive r2, self, key, val
     return 1
+
+[case testInvalidMypycAttr]
+from mypy_extensions import mypyc_attr
+
+@mypyc_attr("allow_interpreted_subclasses", "invalid_arg")  # E: "invalid_arg" is not a supported "mypyc_attr" \
+                                                            # N: supported keys: "allow_interpreted_subclasses", "free_list_len", "native_class", "serializable"
+class InvalidArg:
+    pass
+@mypyc_attr(invalid_kwarg=True)  # E: "invalid_kwarg" is not a supported "mypyc_attr" \
+                                 # N: supported keys: "allow_interpreted_subclasses", "free_list_len", "native_class", "serializable"
+class InvalidKwarg:
+    pass
+@mypyc_attr(str())  # E: All "mypyc_attr" positional arguments must be string literals.
+class InvalidLiteral:
+    pass