lint: add typing annotations to pass pre-commit

Pre-commit seems to run mypy in parallel batches, each with about 20
files. In this mode, certain tests that pass when running mypy all in
once or file-by-file, fail.

In the current state, both running mypy without arguments or running it
in pre-commit seem to work.

Author: dvarrazzo

.pre-commit-config.yaml

@@ -22,5 +22,5 @@ repos:
       - id: mypy
         name: mypy
         language: system
-        entry: mypy --pretty
+        entry: mypy --pretty --follow-imports=silent
         files: \.py[i]?$

psycopg/psycopg/_cmodule.py

@@ -1,3 +1,4 @@
+# mypy: disable-error-code="import-not-found, attr-defined"
 """
 Simplify access to the _psycopg module
 """
@@ -6,19 +7,29 @@
 
 from __future__ import annotations
 
+from types import ModuleType
 from . import pq
 
 __version__: str | None = None
+_psycopg: ModuleType
 
 # Note: "c" must the first attempt so that mypy associates the variable the
 # right module interface. It will not result Optional, but hey.
 if pq.__impl__ == "c":
-    from psycopg_c import _psycopg as _psycopg
-    from psycopg_c import __version__ as __version__  # noqa: F401
+    import psycopg_c._psycopg
+
+    _psycopg = psycopg_c._psycopg
+    __version__ = psycopg_c.__version__
+
 elif pq.__impl__ == "binary":
-    from psycopg_binary import _psycopg as _psycopg  # type: ignore
-    from psycopg_binary import __version__ as __version__  # type: ignore  # noqa: F401
+    import psycopg_binary._psycopg
+
+    _psycopg = psycopg_binary._psycopg
+    __version__ = psycopg_binary.__version__
+
 elif pq.__impl__ == "python":
-    _psycopg = None  # type: ignore
+
+    _psycopg = None  # type: ignore[assignment]
+
 else:
     raise ImportError(f"can't find _psycopg optimised module in {pq.__impl__!r}")

psycopg/psycopg/_connection_base.py

@@ -482,7 +482,7 @@ def _exec_command(
         else:
             self.pgconn.send_query_params(command, None, result_format=result_format)
 
-        result = (yield from generators.execute(self.pgconn))[-1]
+        result: PGresult = (yield from generators.execute(self.pgconn))[-1]
         if result.status != COMMAND_OK and result.status != TUPLES_OK:
             if result.status == FATAL_ERROR:
                 raise e.error_from_result(result, encoding=self.pgconn._encoding)

psycopg/psycopg/_copy_base.py

@@ -216,10 +216,11 @@ def __init__(self, transformer: Transformer, encoding: str = "utf-8"):
         self._encoding = encoding
 
     def parse_row(self, data: Buffer) -> tuple[Any, ...] | None:
+        rv: tuple[Any, ...] | None = None
         if data:
-            return parse_row_text(data, self.transformer)
-        else:
-            return None
+            rv = parse_row_text(data, self.transformer)
+
+        return rv
 
     def write(self, buffer: Buffer | str) -> Buffer:
         data = self._ensure_bytes(buffer)
@@ -260,6 +261,8 @@ def __init__(self, transformer: Transformer):
         self._signature_sent = False
 
     def parse_row(self, data: Buffer) -> tuple[Any, ...] | None:
+        rv: tuple[Any, ...] | None = None
+
         if not self._signature_sent:
             if data[: len(_binary_signature)] != _binary_signature:
                 raise e.DataError(
@@ -268,10 +271,10 @@ def parse_row(self, data: Buffer) -> tuple[Any, ...] | None:
             self._signature_sent = True
             data = data[len(_binary_signature) :]
 
-        elif data == _binary_trailer:
-            return None
+        if data != _binary_trailer:
+            rv = parse_row_binary(data, self.transformer)
 
-        return parse_row_binary(data, self.transformer)
+        return rv
 
     def write(self, buffer: Buffer | str) -> Buffer:
         data = self._ensure_bytes(buffer)

psycopg/psycopg/_cursor_base.py

@@ -334,7 +334,7 @@ def _stream_send_gen(
         yield from send(self._pgconn)
 
     def _stream_fetchone_gen(self, first: bool) -> PQGen[PGresult | None]:
-        res = yield from fetch(self._pgconn)
+        res: PGresult | None = yield from fetch(self._pgconn)
         if res is None:
             return None
 

pyproject.toml

@@ -50,6 +50,7 @@ exclude = '''(?x)(
 [[tool.mypy.overrides]]
 module = [
     "numpy.*",
+    "polib",
     "shapely.*",
 ]
 ignore_missing_imports = true

tests/scripts/pipeline-demo.py

@@ -190,10 +190,7 @@ def pipeline_demo_pq(rows_to_send: int, logger: logging.Logger) -> None:
     ):
         while results_queue:
             fetched = waiting.wait(
-                pipeline_communicate(
-                    pgconn,  # type: ignore[arg-type]
-                    commands,
-                ),
+                pipeline_communicate(pgconn, commands),
                 pgconn.socket,
             )
             assert not commands, commands
@@ -216,10 +213,7 @@ async def pipeline_demo_pq_async(rows_to_send: int, logger: logging.Logger) -> N
     ):
         while results_queue:
             fetched = await waiting.wait_async(
-                pipeline_communicate(
-                    pgconn,  # type: ignore[arg-type]
-                    commands,
-                ),
+                pipeline_communicate(pgconn, commands),
                 pgconn.socket,
             )
             assert not commands, commands

tests/test_adapt.py

@@ -427,10 +427,7 @@ def test_optimised_adapters():
         obj = getattr(_psycopg, n)
         if not isinstance(obj, type):
             continue
-        if not issubclass(
-            obj,
-            (_psycopg.CDumper, _psycopg.CLoader),  # type: ignore[attr-defined]
-        ):
+        if not issubclass(obj, (_psycopg.CDumper, _psycopg.CLoader)):
             continue
         c_adapters[n] = obj
 

tests/types/test_array.py

@@ -8,6 +8,7 @@
 import pytest
 
 import psycopg
+import psycopg.types.numeric
 from psycopg import pq
 from psycopg import sql
 from psycopg.adapt import PyFormat, Transformer, Dumper