d42-typing

d42-typing is a Python package designed to enhance type-checking capabilities within the d42 ecosystem. This package introduces generated type definitions that make it easier to work with D42 schemas by providing a more structured and robust type-checking mechanism.

• Features
• How it works
• Example
  • Scalar schema
  • Dict schema
  • Working type hints for PyCharm
• Installation & Usage
  • How to configurate type auto-generation in PyCharm

Features

• Type Definitions: Provides comprehensive type definitions for various entities within Device42.
• Improved Type Checking: Enhances code safety and reliability by utilizing Python's type hints.

How it works

• Generates Python type hints from d42 schemas.
• Creates .pyi files for each schema file in a specified folder (or default).
• Provides overloads for the fake method from d42 library in stubs folder.

Example

Scalar schema

from d42 import schema

# --- scalar.py
ValueSchema = schema.int | schema.float

# --- scalar.pyi 
from ... import ...

ValueSchema: Union[IntSchema, FloatSchema]

# --- _stubs/d42/fake.pyi
from ... import ...

@overload
def fake(schema: ValueSchema) -> Union[int, float]:
    pass

Dict schema

# --- dict.py
from d42 import schema

DictSchema = schema.dict({
    'id': schema.int,
    'name': schema.str('default_name') | schema.str('custom_name'),
    'phone': schema.str | schema.none,
})

# --- dict.pyi
from ... import ...

class _D42MetaUserSchema(type):

    @overload
    def __getitem__(cls, arg: Literal['id']) -> IntSchema:
        pass

    @overload
    def __getitem__(cls, arg: Literal['name']) -> StrSchema:
        pass

    @overload
    def __getitem__(cls, arg: Literal['phone']) -> Union[StrSchema, NoneSchema]:
        pass

    def __mod__(self, other):
        pass

    def __add__(self, other):
        pass

class UserSchema(metaclass=_D42MetaUserSchema):

    class type(TypedDict, total=False):
        id: IntSchema.type
        name: StrSchema.type
        phone: Union[StrSchema.type, NoneSchema.type]

# --- _stubs/d42/fake.pyi
from typing import overload
from typing import Type
from _tests.schemas.test import UserSchema

@overload
def fake(schema: Type[UserSchema]) -> UserSchema.type:
    pass

Working type hints for PyCharm

Installation & Usage

To install d42-typing, use the following command:

pip install d42-typing

1. Generate type hints, run the following command:

d42-typing --path-to-schemas scenarios/schemas -a -v -s _stubs
# d42-typing --help

2. Configure mypy for correct type-checking:

[mypy]
mypy_path = _stubs

3. Add _stubs/ directory in .gitignore.
4. Mark _stubs/ directory as Sources Root in PyCharm.

How to configurate type auto-generation in PyCharm

1. Set FileWatcher in PyCharm for auto-generating stubs

   • Go to Pycharm → Settings → Tools → File Watchers
   • Set the scope pattern: file[project]:packages/e2e/schemas/*.py

   

2. Hide .pyi files (if needed):

   Go to Settings → Editor → File Types → Ignored Files and Folders tab