Initial commit

Author: ikonst

.gitignore

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+*~
+*.pyc
+*.pyo
+*.pyt
+*.pytc
+*.egg-info
+.*.swp
+.DS_Store
+.cache/
+.idea/
+.coverage
+.mypy_cache
+.pytest_cache

.pre-commit-config.yaml

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+repos:
+    - repo: https://github.com/asottile/reorder_python_imports
+      rev: v1.3.4
+      hooks:
+          - id: reorder-python-imports
+    - repo: https://github.com/pre-commit/pre-commit-hooks
+      rev: v2.0.0
+      hooks:
+          - id: check-ast
+          - id: check-docstring-first
+          - id: check-executables-have-shebangs
+          - id: check-json
+          - id: check-merge-conflict
+          - id: check-yaml
+          - id: debug-statements
+          - id: end-of-file-fixer
+          - id: flake8
+            additional_dependencies:
+                - flake8>=3.6.0,<4
+                - flake8-bugbear
+                - flake8-builtins
+                - flake8-comprehensions
+                - flake8-commas
+          - id: trailing-whitespace
+    - repo: https://github.com/asottile/yesqa
+      rev: v0.0.8
+      hooks:
+          - id: yesqa
+            additional_dependencies:
+                - flake8>=3.6.0,<4
+                - flake8-bugbear
+                - flake8-builtins
+                - flake8-comprehensions
+                - flake8-commas
+    - repo: https://github.com/asottile/pyupgrade
+      rev: v1.11.0
+      hooks:
+        - id: pyupgrade
+    # Switch to standard pre-commit mypy when a version of mypy is released that has:
+    # - mypy.plugin.Plugin.lookup_fully_qualified
+    # - typeshed with https://github.com/ikonst/typeshed/tree/pynamodb-attr-nullable
+    - repo: local
+      hooks:
+        - id: mypy
+          name: mypy
+          entry: mypy
+          language: python
+          'types': [python]
+          args: ["--ignore-missing-imports", "--scripts-are-modules", "--show-traceback"]
+          additional_dependencies: [
+            '-U', 'git+git://github.com/ikonst/mypy.git@5a8dffb5bd94bda615703f6994d39ea1c7c02ef5',
+          ]
+          exclude: >
+            (?x)^(
+              tests/.*|
+            )$

LICENSE

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+   limitations under the License.

README.md

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+# pynamodb-mypy
+
+A plugin for mypy which gives it deeper understanding of PynamoDB (beyond what's possible through type stubs).
+
+# Usage
+
+Add it to the `plugins` option of the `[mypy]` section in your mypy.ini:
+```ini
+[mypy]
+plugins = pynamodb_mypy
+```
+
+# Nullable attributes
+
+When declaring attributes with `null=True`, the value types would become optional. For example:
+```py
+from pynamodb.attributes import UnicodeAttribute
+from pynamodb.models import Model
+
+class MyModel(Model):
+  my_key = UnicodeAttribute()
+  my_value = UnicodeAttribute(null=True)
+
+...
+my_model = MyModel.get('key')
+if my_model.my_value.lower() == 'foo':  # error: Item "None" of "Optional[str]" has no attribute "lower"
+   print("Value is foo")
+```
+would have to be changed to, e.g.:
+```py
+if my_model.my_value and my_model.my_value.lower() == 'foo':
+   print("Value is foo")
+```

pynamodb_mypy/__init__.py

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+from typing import Callable
+from typing import Optional
+from typing import Type
+
+import mypy.types
+from mypy.nodes import NameExpr
+from mypy.nodes import TypeInfo
+from mypy.plugin import FunctionContext
+from mypy.plugin import Plugin
+
+ATTR_FULL_NAME = 'pynamodb.attributes.Attribute'
+NULL_ATTR_FULL_NAME = 'pynamodb.attributes._NullableAttribute'
+
+
+class PynamodbPlugin(Plugin):
+    @staticmethod
+    def _get_attribute_underlying_type(attribute_class: TypeInfo) -> Optional[mypy.types.Type]:
+        """
+        e.g. for `class MyAttribute(Attribute[int])`, this will return `int`.
+        """
+        for base_instance in attribute_class.bases:
+            if base_instance.type.fullname() == ATTR_FULL_NAME:
+                return base_instance.args[0]
+        return None
+
+    def get_function_hook(self, fullname: str) -> Optional[Callable[[FunctionContext], mypy.types.Type]]:
+        symbol_table_node = self.lookup_fully_qualified(fullname)
+        if not symbol_table_node:
+            return None
+
+        if isinstance(symbol_table_node.node, TypeInfo):
+            underlying_type = self._get_attribute_underlying_type(symbol_table_node.node)
+            if underlying_type:
+                _underlying_type = underlying_type  # https://github.com/python/mypy/issues/4297
+                return lambda ctx: _attribute_instantiation_hook(ctx, _underlying_type)
+
+        return None
+
+
+def _attribute_instantiation_hook(ctx: FunctionContext,
+                                  underlying_type: mypy.types.Type) -> mypy.types.Type:
+    """
+    Handles attribute instantiation, e.g. MyAttribute(null=True)
+    """
+    args = dict(zip(ctx.callee_arg_names, ctx.args))
+
+    # If initializer is passed null=True, wrap in _NullableAttribute
+    # to make the underlying type optional
+    null_arg_exprs = args.get('null')
+    if null_arg_exprs and len(null_arg_exprs) == 1:
+        (null_arg_expr,) = null_arg_exprs
+        if (
+            not isinstance(null_arg_expr, NameExpr) or
+            null_arg_expr.fullname not in ('builtins.False', 'builtins.True')
+        ):
+            ctx.api.fail("'null' argument is not constant False or True, "
+                         "cannot deduce optionality", ctx.context)
+            return ctx.default_return_type
+
+        if null_arg_expr.fullname == 'builtins.True':
+            return ctx.api.named_generic_type(NULL_ATTR_FULL_NAME, [
+                ctx.default_return_type,
+                underlying_type,
+            ])
+
+    return ctx.default_return_type
+
+
+def plugin(version: str) -> Type[PynamodbPlugin]:
+    return PynamodbPlugin

requirements.txt

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+-e .
+# Remove this line after mypy-0.660 is released
+-e git+git://github.com/ikonst/mypy.git@5a8dffb5bd94bda615703f6994d39ea1c7c02ef5#egg=mypy
+pre-commit
+pytest
+pytest-cov
+pytest-mock