Proposal for supporting call-overload errors

README.md

@@ -67,13 +67,18 @@ the file:
 * `# F: <msg>` - we expect a mypy fatal error message
 * `# R: <msg>` - we expect a mypy note message `Revealed type is
   '<msg>'`. This is useful to easily check `reveal_type` output:
+
      ```python
      @pytest.mark.mypy_testing
      def mypy_use_reveal_type():
          reveal_type(123)  # N: Revealed type is 'Literal[123]?'
          reveal_type(456)  # R: Literal[456]?
      ```
 
+* `# O: <msg>` - we expect a mypy error message and additionally suppress any
+  notes on the same line. This is useful to test for errors such as
+  `call-overload` where mypy provides extra details in notes along with the error.
+
 ## mypy Error Code Matching
 
 The algorithm matching messages parses mypy error code both in the

src/pytest_mypy_testing/message.py

@@ -41,6 +41,7 @@ def __repr__(self) -> str:
     "W": Severity.WARNING,
     "E": Severity.ERROR,
     "F": Severity.FATAL,
+    "O": Severity.ERROR,
 }
 
 _COMMENT_MESSAGES = frozenset(
@@ -64,6 +65,7 @@ class Message:
     message: str = ""
     revealed_type: Optional[str] = None
     error_code: Optional[str] = None
+    suppress_notes: bool = False
 
     TupleType = Tuple[
         str, int, Optional[int], Severity, str, Optional[str], Optional[str]
@@ -73,7 +75,7 @@ class Message:
 
     COMMENT_RE = re.compile(
         r"^(?:# *type: *ignore *)?(?:# *)?"
-        r"(?P<severity>[RENW]):"
+        r"(?P<severity>[RENWO]):"
         r"((?P<colno>\d+):)?"
         r" *"
         r"(?P<message_and_error_code>[^#]*)"
@@ -239,9 +241,11 @@ def from_comment(
         """Create message object from Python *comment*.
 
         >>> Message.from_comment("foo.py", 1, "R: foo")
-        Message(filename='foo.py', lineno=1, colno=None, severity=Severity.NOTE, message="Revealed type is 'foo'", revealed_type='foo', error_code=None)
+        Message(filename='foo.py', lineno=1, colno=None, severity=Severity.NOTE, message="Revealed type is 'foo'", revealed_type='foo', error_code=None, suppress_notes=False)
         >>> Message.from_comment("foo.py", 1, "E: [assignment]")
-        Message(filename='foo.py', lineno=1, colno=None, severity=Severity.ERROR, message='', revealed_type=None, error_code='assignment')
+        Message(filename='foo.py', lineno=1, colno=None, severity=Severity.ERROR, message='', revealed_type=None, error_code='assignment', suppress_notes=False)
+        >>> Message.from_comment("foo.py", 1, "O: [call-overload]")
+        Message(filename='foo.py', lineno=1, colno=None, severity=Severity.ERROR, message='', revealed_type=None, error_code='call-overload', suppress_notes=True)
         """
         m = cls.COMMENT_RE.match(comment.strip())
         if not m:
@@ -250,11 +254,15 @@ def from_comment(
         message, error_code = cls.__split_message_and_error_code(
             m.group("message_and_error_code")
         )
+
+        suppress_notes = False
+        revealed_type = None
         if m.group("severity") == "R":
             revealed_type = message
             message = "Revealed type is {!r}".format(message)
-        else:
-            revealed_type = None
+        elif m.group("severity") == "O":
+            suppress_notes = True
+
         return Message(
             str(filename),
             lineno=lineno,
@@ -263,6 +271,7 @@ def from_comment(
             message=message,
             revealed_type=revealed_type,
             error_code=error_code,
+            suppress_notes=suppress_notes,
         )
 
     @classmethod

src/pytest_mypy_testing/output_processing.py

@@ -106,6 +106,17 @@ def _chunk_to_dict(chunk: Sequence[Message]) -> Dict[int, List[Message]]:
 
     errors: List[OutputMismatch] = []
 
+    # If an expected message has specified to suppress notes on a line, then
+    # drop them before performing the comparison.
+    suppress_notes_lines = {
+        msg.lineno for msg in expected_messages if msg.suppress_notes
+    }
+    actual_messages = [
+        msg
+        for msg in actual_messages
+        if msg.lineno not in suppress_notes_lines or msg.severity != Severity.NOTE
+    ]
+
     for a_chunk, b_chunk in iter_msg_seq_diff_chunks(
         actual_messages, expected_messages
     ):

tests/test_basics.mypy-testing

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: CC0-1.0
 
 import pytest
+import dataclasses
 
 
 @pytest.mark.mypy_testing
@@ -97,3 +98,11 @@ def mypy_test_xfail_missing_note():
 @pytest.mark.xfail
 def mypy_test_xfail_unexpected_note():
     reveal_type([])  # unexpected message
+
+
+@pytest.mark.mypy_testing
+def mypy_test_suppress_notes():
+    # Check the use of the "O" severity
+    dataclasses.field(default=123, default_factory=lambda: 456) # O: [call-overload]
+    # Check that notes on other lines are not suppressed
+    reveal_type(123) # N: Revealed type is 'Literal[123]?'