Update mypy to 0.720

mypy 0.720 includes a new semantic analyzer that it uses by default. It
mostly still works fine with Tildes's code, except that it doesn't
understand that @hybrid_property is very similar to @property, and it
also fixes a bug I was taking advantage of before to get mypy to not
complain about a @property that returns a different type than you set it
to.

This uses the TYPE_CHECKING constant (which is only ever true when mypy
is currently analyzing the code) to effectively replace @hybrid_property
with @property so that mypy understands it.

tildes/requirements.txt

@@ -34,7 +34,7 @@ MarkupSafe==1.1.1
 marshmallow==2.19.5
 mccabe==0.6.1
 more-itertools==7.1.0
-mypy==0.711
+mypy==0.720
 mypy-extensions==0.4.1
 packaging==19.0
 parso==0.5.1
@@ -101,6 +101,7 @@ traitlets==4.3.2
 transaction==2.4.0
 translationstring==1.3
 typed-ast==1.4.0
+typing-extensions==3.7.4
 urllib3==1.25.3
 venusian==1.2.0
 waitress==1.3.0

tildes/tildes/models/comment/comment.py

@@ -5,11 +5,10 @@
 
 from collections import Counter
 from datetime import datetime, timedelta
-from typing import Any, Optional, Sequence, Tuple
+from typing import Any, Optional, Sequence, Tuple, TYPE_CHECKING
 
 from pyramid.security import Allow, Authenticated, Deny, DENY_ALL, Everyone
 from sqlalchemy import Boolean, Column, ForeignKey, Integer, Text, TIMESTAMP
-from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.orm import deferred, relationship
 from sqlalchemy.sql.expression import text
 
@@ -23,6 +22,10 @@ from tildes.models.topic import Topic
 from tildes.models.user import User
 from tildes.schemas.comment import CommentSchema
 
+if TYPE_CHECKING:  # workaround for mypy issues with @hybrid_property
+    from builtins import property as hybrid_property
+else:
+    from sqlalchemy.ext.hybrid import hybrid_property
 
 # edits inside this period after creation will not mark the comment as edited
 EDIT_GRACE_PERIOD = timedelta(minutes=5)
@@ -96,7 +99,7 @@ class Comment(DatabaseModel):
         """Return the comment's markdown."""
         return self._markdown
 
-    @markdown.setter  # type: ignore
+    @markdown.setter
     def markdown(self, new_markdown: str) -> None:
         """Set the comment's markdown and render its HTML."""
         if new_markdown == self.markdown:

tildes/tildes/models/topic/topic.py

@@ -4,7 +4,7 @@
 """Contains the Topic class."""
 
 from datetime import datetime, timedelta
-from typing import Any, Dict, List, Optional, Sequence, Tuple
+from typing import Any, Dict, List, Optional, Sequence, Tuple, TYPE_CHECKING
 
 from pyramid.security import Allow, Authenticated, Deny, DENY_ALL, Everyone
 from sqlalchemy import (
@@ -18,7 +18,6 @@ from sqlalchemy import (
     TIMESTAMP,
 )
 from sqlalchemy.dialects.postgresql import ENUM, JSONB, TSVECTOR
-from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.ext.mutable import MutableDict
 from sqlalchemy.orm import deferred, relationship
 from sqlalchemy.sql.expression import text
@@ -38,6 +37,10 @@ from tildes.models.group import Group
 from tildes.models.user import User
 from tildes.schemas.topic import TITLE_MAX_LENGTH, TopicSchema
 
+if TYPE_CHECKING:  # workaround for mypy issues with @hybrid_property
+    from builtins import property as hybrid_property
+else:
+    from sqlalchemy.ext.hybrid import hybrid_property
 
 # edits inside this period after creation will not mark the topic as edited
 EDIT_GRACE_PERIOD = timedelta(minutes=5)
@@ -143,7 +146,7 @@ class Topic(DatabaseModel):
 
         return self._markdown
 
-    @markdown.setter  # type: ignore
+    @markdown.setter
     def markdown(self, new_markdown: str) -> None:
         """Set the topic's markdown and render its HTML."""
         if not self.is_text_type:
@@ -171,7 +174,7 @@ class Topic(DatabaseModel):
 
         return sorted_tags
 
-    @tags.setter  # type: ignore
+    @tags.setter
     def tags(self, new_tags: List[str]) -> None:
         self._tags = new_tags
 

tildes/tildes/models/user/user.py

@@ -172,7 +172,7 @@ class User(DatabaseModel):
     def __init__(self, username: str, password: str):
         """Create a new user account."""
         self.username = username
-        self.password = password
+        self.password = password  # type: ignore
 
     def __acl__(self) -> Sequence[Tuple[str, Any, str]]:
         """Pyramid security ACL."""