Implement support for flexible matching of mypy error codes

Author: David Fritzsche

.gitignore

@@ -1,5 +1,14 @@
 # SPDX-FileCopyrightText: David Fritzsche
 # SPDX-License-Identifier: CC0-1.0
+
+!.bumpversion.cfg
+!.bumpversion.cfg.license
+!.editorconfig
+!.flake8
+!.gitattributes
+!.gitignore
+!.isort.cfg
+!/.github
 *.bak
 *.egg-info
 *.pyc

README.md

@@ -73,6 +73,24 @@ the file:
          reveal_type(456)  # R: Literal[456]?
      ```
 
+## mypy Error Codes
+
+The algorithm matching messages parses mypy error code both in the
+output generated by mypy and in the Python comments. If both the mypy
+output and the Python comment contain an error code, then the codes
+must match. So the following test case expects that mypy writes out an
+``assignment`` error code:
+
+``` python
+@pytest.mark.mypy_testing
+def mypy_test_invalid_assignment() -> None:
+    foo = "abc"
+    foo = 123  # E: Incompatible types in assignment (expression has type "int", variable has type "str")  [assignment]
+```
+
+If the Python comment does not contain an error code, then the error
+code written out by mypy (if any) is simply ignored.
+
 
 ## Skipping and Expected Failures
 
@@ -96,6 +114,10 @@ decorators are extracted from the ast.
 
 # Changelog
 
+## Upcoming
+
+* Implement support for flexible matching of mypy error codes
+
 ## v0.0.12
 
 * Allow Windows drives in filename (#17, #34)

mypy_tests/test_mypy_tests_in_test_file.py

@@ -1,12 +1,15 @@
 # SPDX-FileCopyrightText: David Fritzsche
 # SPDX-License-Identifier: CC0-1.0
 
+# flake8: noqa
+# ruff: noqa
+
 import pytest
 
 
 @pytest.mark.mypy_testing
 def err():
-    import foo  # E: Cannot find implementation or library stub for module named 'foo'  # noqa
+    import foo  # E: Cannot find implementation or library stub for module named 'foo'
 
 
 @pytest.mark.mypy_testing

src/pytest_mypy_testing/message.py

@@ -61,24 +61,31 @@ class Message:
     severity: Severity
     message: str
     revealed_type: Optional[str] = None
+    error_code: Optional[str] = None
 
-    TupleType = Tuple[str, int, Optional[int], Severity, str, Optional[str]]
+    TupleType = Tuple[
+        str, int, Optional[int], Severity, str, Optional[str], Optional[str]
+    ]
 
     _prefix: str = dataclasses.field(init=False, repr=False, default="")
 
     COMMENT_RE = re.compile(
         r"^(?:# *type: *ignore *)?(?:# *)?"
         r"(?P<severity>[RENW]):"
         r"((?P<colno>\d+):)? *"
-        r"(?P<message>[^#]*)(?:#.*?)?$"
+        r"(?P<message>[^#]*?)"
+        r"(?: +\[(?P<error_code>[^\]]*)\])?"
+        r"(?:#.*?)?$"
     )
 
     OUTPUT_RE = re.compile(
         r"^(?P<fname>([a-zA-Z]:)?[^:]+):"
         r"(?P<lineno>[0-9]+):"
         r"((?P<colno>[0-9]+):)?"
         r" *(?P<severity>(error|note|warning)):"
-        r"(?P<message>.*)$"
+        r"(?P<message>.*?)"
+        r"(?: +\[(?P<error_code>[^\]]*)\])?"
+        r"$"
     )
 
     _OUTPUT_REVEALED_RE = re.compile(
@@ -130,12 +137,15 @@ def astuple(self, *, normalized: bool = False) -> "Message.TupleType":
             self.severity,
             self.normalized_message if normalized else self.message,
             self.revealed_type,
+            self.error_code,
         )
 
     def is_comment(self) -> bool:
         return (self.severity, self.message) in _COMMENT_MESSAGES
 
-    def _as_short_tuple(self, *, normalized: bool = False) -> "Message.TupleType":
+    def _as_short_tuple(
+        self, *, normalized: bool = False, default_error_code: Optional[str] = None
+    ) -> "Message.TupleType":
         if normalized:
             message = self.normalized_message
         else:
@@ -147,14 +157,20 @@ def _as_short_tuple(self, *, normalized: bool = False) -> "Message.TupleType":
             self.severity,
             message,
             self.revealed_type,
+            self.error_code or default_error_code,
         )
 
     def __eq__(self, other):
         if isinstance(other, Message):
+            default_error_code = self.error_code or other.error_code
             if self.colno is None or other.colno is None:
-                return self._as_short_tuple(normalized=True) == other._as_short_tuple(
-                    normalized=True
+                a = self._as_short_tuple(
+                    normalized=True, default_error_code=default_error_code
+                )
+                b = other._as_short_tuple(
+                    normalized=True, default_error_code=default_error_code
                 )
+                return a == b
             else:
                 return self.astuple(normalized=True) == other.astuple(normalized=True)
         else:
@@ -192,6 +208,7 @@ def from_comment(
             severity=Severity.from_string(m.group("severity")),
             message=message,
             revealed_type=revealed_type,
+            error_code=m.group("error_code") or None,
         )
 
     @classmethod

tests/test_message.py

@@ -1,6 +1,8 @@
 # SPDX-FileCopyrightText: David Fritzsche
 # SPDX-License-Identifier: CC0-1.0
 
+from typing import Optional
+
 import pytest
 
 from pytest_mypy_testing.message import Message, Severity
@@ -14,26 +16,35 @@ def test_init_severity(string: str, expected: Severity):
 
 
 @pytest.mark.parametrize(
-    "filename,comment,severity,message",
+    "filename,comment,severity,message,error_code",
     [
-        ("z.py", "# E: bar", Severity.ERROR, "bar"),
-        ("z.py", "#type:ignore# W: bar", Severity.WARNING, "bar"),
-        ("z.py", "# type: ignore # W: bar", Severity.WARNING, "bar"),
-        ("z.py", "# R: bar", Severity.NOTE, "Revealed type is 'bar'"),
+        ("z.py", "# E: bar", Severity.ERROR, "bar", None),
+        ("z.py", "# E: bar", Severity.ERROR, "bar", "foo"),
+        ("z.py", "# E: bar [foo]", Severity.ERROR, "bar", "foo"),
+        ("z.py", "# E: bar [foo]", Severity.ERROR, "bar", ""),
+        ("z.py", "#type:ignore# W: bar", Severity.WARNING, "bar", None),
+        ("z.py", "# type: ignore # W: bar", Severity.WARNING, "bar", None),
+        ("z.py", "# R: bar", Severity.NOTE, "Revealed type is 'bar'", None),
     ],
 )
 def test_message_from_comment(
-    filename: str, comment: str, severity: Severity, message: str
+    filename: str,
+    comment: str,
+    severity: Severity,
+    message: str,
+    error_code: Optional[str],
 ):
     lineno = 123
+    actual = Message.from_comment(filename, lineno, comment)
     expected = Message(
         filename=filename,
         lineno=lineno,
         colno=None,
         severity=severity,
         message=message,
+        error_code=error_code,
     )
-    assert Message.from_comment(filename, lineno, comment) == expected
+    assert actual == expected
 
 
 def test_message_from_invalid_comment():