Tips & Tricks

TYPE_CHECKING

Do you use TYPE_CHECKING in bricks? TYPE_CHECKING is a special constant that is True for static type checkers, but False at runtime.

Example:

if TYPE_CHECKING:
    from mypy_boto3_s3.service_resource import Object as S3Object

The poly check command will identify the import and expect it to be defined as a dependency. Usually, these dev-specific dependencies are added as dev-dependencies (and that is correct).

This means that the poly check command will report it as a missing dependency.

Solution

To resolve this, you can add optional dependencies in the projects that use the brick with the TYPE_CHECKING constant.

Example, using the dev-only "boto3-stubs" library:

# add the dev-dependencies for every project that is using the brick
[project.optional-dependencies]
local-dev = ["boto3-stubs[s3]"]