Type-check Model.__init__

Author: ikonst

.github/workflows/release.yml

@@ -0,0 +1,28 @@
+name: Release
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.x'
+    - name: Install build dependencies
+      run: |
+        pip install build
+
+    - name: Build packages
+      run: |
+        python -m build
+
+    - name: Publish to PyPI
+      uses: pypa/gh-action-pypi-publish@release/v1
+      with:
+        user: __token__
+        password: ${{ secrets.PYPI_API_TOKEN }}

.github/workflows/test.yml

@@ -0,0 +1,30 @@
+name: Python package
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.8", "3.9", "3.10"]
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v3
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install test dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+    - name: Test with pytest
+      run: |
+        pytest -v

.gitignore

@@ -14,3 +14,5 @@
 build/
 dist/
 venv/
+tests/playground.py
+touch.sh

.pre-commit-config.yaml

@@ -1,10 +1,10 @@
 repos:
     - repo: https://github.com/asottile/reorder_python_imports
-      rev: v1.3.4
+      rev: v3.8.5
       hooks:
           - id: reorder-python-imports
     - repo: https://github.com/pre-commit/pre-commit-hooks
-      rev: v2.0.0
+      rev: v4.3.0
       hooks:
           - id: check-ast
           - id: check-docstring-first
@@ -15,19 +15,24 @@ repos:
           - id: debug-statements
           - id: end-of-file-fixer
           - id: trailing-whitespace
-    - repo: https://gitlab.com/pycqa/flake8
-      rev: 3.8.1
-      hooks:
-          - id: flake8
-            additional_dependencies:
-            -   flake8-bugbear==18.8.0
-            -   flake8-comprehensions==1.4.1
-            -   flake8-tidy-imports==1.1.0
     - repo: https://github.com/asottile/pyupgrade
-      rev: v1.11.0
+      rev: v3.1.0
       hooks:
         - id: pyupgrade
+          args: [--py38-plus]
+    - repo: https://github.com/psf/black
+      rev: 22.8.0
+      hooks:
+          - id: black
+    - repo: https://github.com/pycqa/flake8
+      rev: 5.0.4
+      hooks:
+          - id: flake8
+            additional_dependencies:
+            -   flake8-bugbear==22.9.23
+            -   flake8-comprehensions==3.10.0
+            -   flake8-tidy-imports==4.8.0
     - repo: https://github.com/pre-commit/mirrors-mypy
-      rev: v0.770
+      rev: v0.982
       hooks:
-        - id: mypy
+         - id: mypy

.travis.yml

@@ -31,3 +31,30 @@ would have to be changed to, e.g.:
 if my_model.my_value and my_model.my_value.lower() == 'foo':
    print("Value is foo")
 ```
+
+# Typed model initializers
+
+When declaring models, the `__init__` method would be typed to accept only the attributes declared in the model. For example:
+```py
+from pynamodb.models import Model
+from pynamodb.attributes import NumberAttribute
+from pynamodb.attributes import UnicodeAttribute
+
+class MyModel(Model):
+  my_key = UnicodeAttribute(hash_key=True)
+  my_value = NumberAttribute(null=True)
+
+# Existing attributes would be enforced:
+_ = MyModel(my_key='key', my_value=42, my_other_value='other_value')  # error: Unexpected keyword argument "my_other_value" for "MyModel"
+
+# Typing would be enforced:
+_ = MyModel(my_key='key', my_value='42')  # error: Argument 2 to "MyModel" has incompatible type "str"; expected "Optional[int]"
+
+# Nullability will be enforced::
+_ = MyModel(my_key='key', my_value=None)
+_ = MyModel(my_key=None, my_value=None)  # error: Argument "my_key" to "MyModel" has incompatible type "None"; expected "str"
+
+# The hash key and range key can also be passed as positional arguments:
+_ = MyModel('key')
+_ = MyModel(42)  # error: Argument 1 to "MyModel" has incompatible type "int"; expected "str"
+```

README.md

@@ -0,0 +1,30 @@
+"""
+Here we'll be using mypy private API shamelessly.
+"""
+from __future__ import annotations
+
+from typing import Optional
+
+import mypy.checker
+import mypy.checkmember
+from mypy.nodes import Context
+from mypy.types import Type
+
+
+def get_descriptor_access_type(ctx: Context, chk: mypy.checker.TypeChecker, descriptor: Type) -> Optional[Type]:
+    """
+    Given a descriptor type, returns the type its __get__ method returns.
+    """
+    return mypy.checkmember.analyze_descriptor_access(
+        descriptor,
+        mypy.checkmember.MemberContext(
+            is_lvalue=False,
+            is_super=False,
+            is_operator=False,
+            original_type=descriptor,
+            context=ctx,
+            msg=chk.msg,
+            chk=chk,
+            self_type=None,
+        ),
+    )