Add a typing example (mypy) test

This example is checked by running mypy on it with both Python and C
implementation.

By having cursor and record values' type declared before assignment, we
make sure that expected types are consistent (otherwise mypy would raise
"Incompatible types in assignment" errors).

Example check_row_factory_connection() is still incomplete because
Connection is not generic on Row; it thus contain many Any types.

diff --git a/psycopg3/tox.ini b/psycopg3/tox.ini
index 94d2ef7977ce62dd4a147ebb6bb7a3b3dda4374f..eff058ecd509db7f56e03f0888a7d66c1009dd14 100644 (file)
--- a/psycopg3/tox.ini
+++ b/psycopg3/tox.ini
@@ -6,7 +6,10 @@ isolated_build = True
 changedir = ..
 commands =
     pytest {posargs}
+    3.9: mypy tests/typing_example.py
 passenv = PG* PSYCOPG3_TEST_DSN PYTEST_ADDOPTS PSYCOPG3_IMPL TRAVIS*
+deps =
+  3.9: mypy
 extras = test
 
 [flake8]

diff --git a/psycopg3_c/tox.ini b/psycopg3_c/tox.ini
index 523e2415490870351573007373b3f62468afc92f..57ec5d4c34ec42614df2d3cb293b7bb51caca546 100644 (file)
--- a/psycopg3_c/tox.ini
+++ b/psycopg3_c/tox.ini
@@ -6,6 +6,8 @@ isolated_build = True
 changedir = ..
 commands =
     pytest {posargs}
+    3.9: mypy tests/typing_example.py
 passenv = PG* PSYCOPG3_TEST_DSN PYTEST_ADDOPTS PSYCOPG3_IMPL TRAVIS*
 deps =
     -e {toxinidir}/../psycopg3[test]
+    3.9: mypy

diff --git a/tests/typing_example.py b/tests/typing_example.py
new file mode 100644 (file)
index 0000000..63cba24
--- /dev/null
+++ b/tests/typing_example.py
@@ -0,0 +1,90 @@
+# flake8: builtins=reveal_type
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Any, Callable, Optional, Sequence
+
+from psycopg3 import BaseCursor, Cursor, ServerCursor, connect
+
+
+def int_row_factory(
+    cursor: BaseCursor[Any, int]
+) -> Callable[[Sequence[int]], int]:
+    return lambda values: values[0] if values else 42
+
+
+@dataclass
+class Person:
+    name: str
+    address: str
+
+    @classmethod
+    def row_factory(
+        cls, cursor: BaseCursor[Any, Person]
+    ) -> Callable[[Sequence[str]], Person]:
+        def mkrow(values: Sequence[str]) -> Person:
+            name, address = values
+            return cls(name, address)
+
+        return mkrow
+
+
+def check_row_factory_cursor() -> None:
+    """Type-check connection.cursor(..., row_factory=<MyRowFactory>) case."""
+    conn = connect()
+
+    cur1: Cursor[Any]
+    cur1 = conn.cursor()
+    r1: Optional[Any]
+    r1 = cur1.fetchone()
+    r1 is not None
+
+    cur2: Cursor[int]
+    r2: Optional[int]
+    with conn.cursor(row_factory=int_row_factory) as cur2:
+        cur2.execute("select 1")
+        r2 = cur2.fetchone()
+        r2 and r2 > 0
+
+    cur3: ServerCursor[Person]
+    persons: Sequence[Person]
+    with conn.cursor(name="s", row_factory=Person.row_factory) as cur3:
+        cur3.execute("select * from persons where name like 'al%'")
+        persons = cur3.fetchall()
+        persons[0].address
+
+
+def check_row_factory_connection() -> None:
+    """Type-check connect(..., row_factory=<MyRowFactory>) or
+    Connection.row_factory cases.
+
+    This example is incomplete because Connection is not generic on Row, hence
+    all the Any, which we aim at getting rid of.
+    """
+    cur1: Cursor[Any]
+    r1: Any
+    conn1 = connect(row_factory=int_row_factory)
+    cur1 = conn1.execute("select 1")
+    r1 = cur1.fetchone()
+    r1 != 0
+    with conn1.cursor() as cur1:
+        cur1.execute("select 2")
+
+    cur2: Cursor[Any]
+    r2: Any
+    conn2 = connect(row_factory=Person.row_factory)
+    cur2 = conn2.execute("select * from persons")
+    r2 = cur2.fetchone()
+    r2 and r2.name
+    with conn2.cursor() as cur2:
+        cur2.execute("select 2")
+
+    cur3: Cursor[Any]
+    r3: Optional[Any]
+    conn3 = connect()
+    cur3 = conn3.execute("select 3")
+    with conn3.cursor() as cur3:
+        cur3.execute("select 42")
+        r3 = cur3.fetchone()
+        r3 and len(r3)