dask/dask

Add static type annotations

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#11,047 opened on Apr 11, 2024

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good first issue

Description

I am having trouble with using Dask in a project that uses PyRight because Dask does not use static type annotations/

Take, da.from_array, for example: https://github.com/dask/dask/blob/b2ec1e1a2361db1e269ba86c7c59d3f6df70a02d/dask/array/core.py#L3307-L3317

Or array.rechunk: https://github.com/dask/dask/blob/b2ec1e1a2361db1e269ba86c7c59d3f6df70a02d/dask/array/rechunk.py#L268-L275

PyRight complains if you use anything but a str for chunks:

image

Argument of type "tuple[Literal[1], Literal[-1], Literal[-1]]" cannot be assigned to parameter "chunks" of type "str" in function "from_array"
  "tuple[Literal[1], Literal[-1], Literal[-1]]" is incompatible with "str"

This happens because in from_array and rechunk, chunks="auto" infers to a str type.

Is there an awareness of this problem? Is there a known solution? If not, is there a plan to fix this?

Contributor guide

Tech stack
python
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Python typingDask array API
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Add type annotations to the 'chunks' parameter in functions like from array and rechunk. These functions accept either a string 'auto' or a tuple of ints. Use typing.Union or overload decorators to properly annotate. See dask/array/core.py around line 3307 and dask/array/rechunk.py around line 268. Test with mypy or pyright to ensure no new errors. Review existing annotations in the repository for style consistency.