Fix psycopg3 detection (#956)

Co-authored-by: Joachim Jablon <ewjoachim@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/howto/django.md

@@ -87,7 +87,7 @@ You can also use other subcommands such as `./manage.py procrastinate defer`.
 
 :::{note}
 Procrastinate generates an app for you using a `Psycopg` (by default) or
-`Aiopg` connector depending on whether `psycopg3` or `aiopg` is
+`Aiopg` connector depending on whether `psycopg` version 3 or `aiopg` is
 installed, and connects using the `DATABASES` settings. If neither library is
 installed, an error will be raised.
 :::

procrastinate/contrib/django/django_connector.py

@@ -127,7 +127,9 @@ def get_worker_connector(self) -> connector.BaseAsyncConnector:
         """
         alias = utils.get_setting("DATABASE_ALIAS", default="default")
 
-        if utils.package_is_installed("psycopg3"):
+        if utils.package_is_installed("psycopg") and utils.package_is_version(
+            "psycopg", 3
+        ):
             from procrastinate import psycopg_connector
 
             return psycopg_connector.PsycopgConnector(

procrastinate/contrib/django/utils.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import importlib.metadata
 import importlib.util
 from typing import Any
 
@@ -36,3 +37,11 @@ def get_setting(name: str, *, default) -> Any:
 
 def package_is_installed(name: str) -> bool:
     return bool(importlib.util.find_spec(name))
+
+
+def package_is_version(name: str, major: int) -> bool:
+    """
+    Check if package's (PEP440) version matches given major version number
+    """
+    version = importlib.metadata.version(name)
+    return bool(version) and version.split(".")[0] == f"{major}"

tests/integration/contrib/django/test_django_connector.py

@@ -82,7 +82,7 @@ def test_execute_query_sync(django_connector):
 @pytest.mark.parametrize(
     "installed, type",
     [
-        ({"psycopg3"}, psycopg_connector.PsycopgConnector),
+        ({"psycopg"}, psycopg_connector.PsycopgConnector),
         ({"aiopg"}, aiopg_connector.AiopgConnector),
     ],
 )

tests/unit/contrib/django/test_utils.py

@@ -27,3 +27,18 @@ def test_get_settings_default():
 )
 def test_package_is_installed(package_name, expected):
     assert utils.package_is_installed(package_name) is expected
+
+
+@pytest.mark.parametrize(
+    "version, version_wanted,expected",
+    [
+        ("3.1.3", 3, True),
+        ("2.1.3", 3, False),
+        ("pytest", 3, False),
+        (None, 3, False),
+    ],
+)
+def test_package_is_version(version, version_wanted, expected, mocker):
+    mocker.patch("importlib.metadata.version", return_value=version)
+
+    assert utils.package_is_version("abcd", version_wanted) is expected