setup: Enable stricter type checking.

This caught the "return instead of raise" bug in meta_project.

conservancy_beancount/plugin/meta_project.py

@@ -43,7 +43,7 @@ class MetaProject(core._NormalizePostingMetadataHook):
     def __init__(self, config: configmod.Config, source_path: Path=PROJECT_DATA_PATH) -> None:
         repo_path = config.repository_path()
         if repo_path is None:
-            return self._config_error("no repository configured")
+            raise self._config_error("no repository configured")
         project_data_path = repo_path / source_path
         source = {'filename': str(project_data_path)}
         try:

conservancy_beancount/rtutil.py

@@ -37,6 +37,7 @@ from typing import (
 RTId = Union[int, str]
 TicketAttachmentIds = Tuple[str, Optional[str]]
 _LinkCache = MutableMapping[TicketAttachmentIds, Optional[str]]
+_URLLookup = Callable[..., Optional[str]]
 
 class RTLinkCache(_LinkCache):
     """Cache RT links to disk
@@ -125,7 +126,8 @@ class RTLinkCache(_LinkCache):
 
     def __len__(self) -> int:
         cursor = self._db.execute('SELECT COUNT(*) FROM RTLinkCache')
-        return cursor.fetchone()[0] + len(self._nourls)
+        count: int = cursor.fetchone()[0]
+        return count + len(self._nourls)
 
     def __getitem__(self, key: TicketAttachmentIds) -> Optional[str]:
         if key in self._nourls:
@@ -134,11 +136,12 @@ class RTLinkCache(_LinkCache):
             'SELECT url FROM RTLinkCache WHERE ticket_id = ? AND attachment_id IS ?',
             key,
         )
-        retval = cursor.fetchone()
-        if retval is None:
+        row = cursor.fetchone()
+        if row is None:
             raise KeyError(key)
         else:
-            return retval[0]
+            retval: str = row[0]
+            return retval
 
     def __setitem__(self, key: TicketAttachmentIds, value: Optional[str]) -> None:
         if value is None:
@@ -191,13 +194,14 @@ class RT:
 
     # mypy complains that the first argument isn't self, but this isn't meant
     # to be a method, it's just an internal decrator.
-    def _cache_method(func: Callable) -> Callable:  # type:ignore[misc]
+    def _cache_method(func: _URLLookup) -> _URLLookup:  # type:ignore[misc]
         @functools.wraps(func)
         def caching_wrapper(self,
                             ticket_id: RTId,
                             attachment_id: Optional[RTId]=None,
-        ) -> str:
+        ) -> Optional[str]:
             cache_key = (str(ticket_id), attachment_id and str(attachment_id))
+            url: Optional[str]
             try:
                 url = self._cache[cache_key]
             except KeyError:

setup.cfg

@@ -3,5 +3,10 @@ test=pytest
 typecheck=pytest --addopts="--mypy conservancy_beancount"
 
 [mypy]
+disallow_any_unimported = True
 show_error_codes = True
+strict_equality = True
+warn_redundant_casts = True
+warn_return_any = True
+warn_unreachable = True
 warn_unused_configs = True