Replace mypy with ty for type checking by aldenks · Pull Request #400 · dynamical-org/reformatters

aldenks · 2026-01-30T03:19:34Z

Summary

Migrate from mypy to ty as the primary type checker for the project. This includes updating all configuration files, CI/CD workflows, documentation, and code to use ty instead of mypy.

Key Changes

Configuration & Setup

Updated pyproject.toml to replace mypy~=1.18 dependency with ty~=0.0.14
Replaced mypy configuration section with ty configuration including Python 3.13 target and custom rule settings
Updated .gitignore and .dockerignore to ignore .ty/ cache directory instead of mypy caches
Updated .pre-commit-config.yaml to run ty check instead of mypy
Removed mypy VSCode extension recommendation from .vscode/extensions.json

CI/CD & Documentation

Updated GitHub Actions workflow to run uv run ty check instead of uv run mypy
Updated AGENTS.md and README.md with ty commands and references
Updated code style guidelines to reference ty type checking instead of mypy strict mode

Code Changes

Removed # type: ignore[import-untyped] comments from untyped library imports (numba, kubernetes, rasterio, etc.) as ty handles these differently
Replaced mypy-specific # type: ignore[...] comments with ty equivalents where needed (e.g., # ty: ignore[not-iterable])
Updated pydantic-related type ignores on @computed_field decorators to work with ty
Improved type annotations in config_models.py for better type safety with codecs handling
Added explicit imports for submodules (e.g., import zarr.abc.store, import sentry_sdk.crons) to satisfy ty's stricter module checking
Updated ruff ignore comments to remove mypy-specific references (UP046, UP047)
Refactored complex type-ignored expressions to be more explicit (e.g., in datasets_cf_compliance_test.py)

Type Checking Configuration

Configured ty to warn on possibly-missing-attribute (for submodule access like zarr.abc)
Configured ty to warn on no-matching-overload (for incomplete xarray stubs)
Configured ty to warn on invalid-method-override (for valid Python covariance patterns)

Notable Details

ty provides better handling of untyped library imports without requiring explicit ignore comments
The migration maintains strict type checking while being more pragmatic about third-party library limitations
All existing type annotations and patterns remain compatible with ty

https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

aldenks · 2026-01-30T03:24:20Z

src/reformatters/noaa/hrrr/forecast_48_hour/region_job.py

                lead_time=lead_time,
                domain="conus",
-                file_type=file_type,
+                file_type=file_type,  # ty: ignore[invalid-argument-type]


this seems typed correctly. maybe our item utility isn't right?

aldenks · 2026-01-30T03:24:22Z

src/reformatters/noaa/hrrr/analysis/region_job.py

                lead_time=lead_time,
                domain="conus",
-                file_type=file_type,
+                file_type=file_type,  # ty: ignore[invalid-argument-type]


this seems typed correctly. maybe our item utility isn't right?

wasn't able to get around this

aldenks · 2026-01-30T03:26:18Z

src/reformatters/noaa/gefs/gefs_config_models.py

-                return gefs_file_type
+                # ty can't narrow through if/elif chain; remaining values are "a" | "b"
+                return gefs_file_type  # ty: ignore[invalid-return-type]


can probably help type checker narrow and remove the ignore with an elif gefs_file_type == "a" or gefs_file_type == "b", and then an else: assert_never(gefs_file_type)

aldenks · 2026-01-30T03:27:58Z

src/reformatters/common/region_job.py

+        # xarray's __getitem__ with a list returns Dataset, but ty stubs say DataArray
+        ds: xr.Dataset = self.template_ds[[v.name for v in self.data_vars]]  # type: ignore[assignment]


Suggested change

# xarray's __getitem__ with a list returns Dataset, but ty stubs say DataArray

ds: xr.Dataset = self.template_ds[[v.name for v in self.data_vars]] # type: ignore[assignment]

ds: xr.Dataset = self.template_ds[[v.name for v in self.data_vars]] # type: ignore[assignment] stubs are wrong

aldenks · 2026-01-30T03:29:19Z

src/reformatters/noaa/gefs/gefs_config_models.py

                case _ as unreachable:
-                    assert_never(unreachable)
+                    assert_never(unreachable)  # ty: ignore[type-assertion-failure]


this should work without an ignore

case _: assert_never(gefs_file_type)

it doesn't, but im going to live with that until ty implements this and then it should start telling us the type ignore is unused

Replace mypy with Astral's ty type checker throughout the project: - Replace mypy dependency with ty in pyproject.toml - Update ty configuration in pyproject.toml - Update pre-commit hook to use ty - Update GitHub Actions workflow to use ty - Update documentation (README.md, AGENTS.md/CLAUDE.md) - Update .vscode/extensions.json to remove mypy extension - Update .gitignore and .dockerignore for ty cache Remove unnecessary type: ignore comments that ty no longer needs: - ty has better type stubs for numba, numcodecs, fsspec, rasterio, yaml, kubernetes - ty handles pydantic's @computed_field properly Add explicit submodule imports for zarr.abc, zarr.storage, sentry_sdk.crons, numcodecs.abc to satisfy ty's stricter submodule attribute checking. Add targeted ty: ignore comments for: - numba's prange (not-iterable - prange is only iterable at runtime in @njit) - Complex type narrowing that ty can't verify through control flow - xarray's ds[[list]] returning DataArray instead of Dataset (stub limitation) Configure ty rules to treat some checks as warnings instead of errors: - invalid-method-override: Subclass return type covariance is valid Python - no-matching-overload: xarray stubs are incomplete - possibly-missing-attribute: For submodule access patterns ty finds issues mypy missed due to better type stubs, while still being fast. https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

@AbstractMethod

Remove ABC and @AbstractMethod decorators from TemplateConfig, RegionJob, and DynamicalDataset base classes. The methods still raise NotImplementedError to enforce implementation at runtime, but ABC is no longer needed since: 1. Parameter names between base and subclass methods now match 2. ty doesn't require ABC for proper type checking of method overrides 3. This allows tests to instantiate base/intermediate classes directly https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

Remove typing.override decorators since they're not used consistently throughout the codebase. Add noqa: ARG002 comments for unused method arguments that are required by the parent class interface. https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

Copilot

Pull request overview

This PR migrates the project’s static type checking from mypy to ty, updating configuration, CI workflows, docs, and code to align with ty’s rules and diagnostics. It also makes small refactors and import adjustments to satisfy ty’s stricter module and attribute checking while keeping runtime behavior unchanged.

Changes:

Replace mypy with ty across tooling: dev dependencies, pyproject.toml config, pre-commit hooks, GitHub Actions workflow, editor recommendations, and ignore patterns.
Update code and tests to remove mypy-specific # type: ignore[...] comments, add ty-specific ignores, and introduce explicit imports / annotations (e.g., for numba, zarr, sentry, rasterio, Timedelta math) to satisfy ty while preserving semantics.
Refactor a few helper functions and expressions (e.g., XML parsing for CF standard names, Timedelta division, band-selection logic for rasterio) for clearer typing and better alignment with ty’s analysis.

Reviewed changes

Copilot reviewed 59 out of 61 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
`uv.lock`	Drops mypy and related deps, adds `ty` and updates dev extras to reflect the new type checker.
`pyproject.toml`	Removes mypy and pydantic-mypy configuration, adds ty rules and dev dependency, and adjusts Ruff comments about PEP 695 generics.
`.pre-commit-config.yaml`	Swaps the local `mypy` hook for a `ty` hook running `uv run ty check`.
`.github/workflows/code-quality.yml`	Updates CI to run `uv run ty check` in place of `uv run mypy`.
`.gitignore` / `.dockerignore`	Generalizes the “mypy” ignore section to “type checkers” while retaining mypy cache patterns.
`.vscode/extensions.json`	Removes the mypy VS Code extension recommendation, leaving only Ruff.
`README.md`	Updates development tooling docs to mention `ty` instead of mypy and adjusts recommended commands.
`AGENTS.md`	Switches tool listing and example commands from mypy to `ty` and updates the code-style guideline to refer to ty ignores.
`tests/noaa/gfs/template_config_test.py`	Removes an obsolete mypy `attr-defined` ignore on `coords.fget` in tests.
`tests/noaa/gfs/forecast/template_config_test.py`	Drops mypy `import-untyped` ignore on `rasterio` in GFS forecast template tests.
`tests/noaa/gefs/forecast_35_day/template_config_test.py`	Same as above for GEFS 35-day forecast template tests.
`tests/example/template_config_test.py`	Updates a commented-out `rasterio` import to remove the mypy-specific ignore.
`tests/common/validation_test.py`	Replaces a broad `zarr` import with more targeted `zarr.core.sync` / `zarr.storage` imports to satisfy ty’s module/attribute checking.
`tests/common/test_storage.py`	Adds `zarr.storage` import to make types like `LocalStore` explicit for ty.
`tests/common/template_config_test.py`	Splits a Timedelta division into a temporary float result to align with ty’s assignment rules, then casts to int.
`tests/common/region_job_test.py`	Imports `dask.array` explicitly and removes unnecessary type ignores around `dask.array.full`; renames unused parameters with `# noqa: ARG002`.
`tests/common/dynamical_dataset_test.py`	Adds explicit imports for `sentry_sdk.crons` and `zarr.errors`; removes pydantic `computed_field` ignore annotations on test config properties.
`tests/common/datasets_cf_compliance_test.py`	Refactors XML parsing into an explicit loop that checks elements and text for `None` instead of relying on union-attr ignores.
`tests/common/common_template_config_subclasses_test.py`	Removes mypy-specific ignores on `template_path` reassignment and fixture return type.
`src/scripts/validation/compare_spatial.py`	Adds targeted `# ty: ignore[...]` comments for attributes on `ref_data` where ty’s analysis is too conservative.
`src/scripts/generate_manual_workflows.py`	Removes mypy `import-untyped` ignore from the `yaml` import.
`src/reformatters/noaa/hrrr/template_config.py`	Cleans up pydantic `computed_field` annotations by dropping mypy-specific `prop-decorator` ignores.
`src/reformatters/noaa/hrrr/region_job.py`	Removes mypy `import-untyped` on `rasterio` and rewrites GRIB band matching from a walrus-comprehension into a clearer loop with explicit list accumulation.
`src/reformatters/noaa/hrrr/forecast_48_hour/template_config.py`	Same computed_field cleanup; no runtime behavior change.
`src/reformatters/noaa/hrrr/forecast_48_hour/region_job.py`	Adds a `# ty: ignore[invalid-argument-type]` where ty can’t see a domain argument’s compatibility, without changing behavior.
`src/reformatters/noaa/hrrr/analysis/template_config.py`	Removes mypy ignores around computed fields on analysis templates.
`src/reformatters/noaa/hrrr/analysis/region_job.py`	Same domain `file_type` argument ty-ignore adjustment as the 48-hour forecast job.
`src/reformatters/noaa/gfs/region_job.py`	Drops mypy import ignore and expands GRIB band selection into an explicit loop mirroring the HRRR change.
`src/reformatters/noaa/gfs/forecast/template_config.py`	Cleans up computed_field decorators for dataset attributes, coords, and data_vars.
`src/reformatters/noaa/gfs/analysis/template_config.py`	Same computed_field cleanup and introduces a named-but-unused `ds` parameter with `# noqa: ARG002` for ty.
`src/reformatters/noaa/gefs/read_data.py`	Removes mypy import ignore, explicitly imports `rasterio.warp`, and rewrites band matching to a loop consistent with other GRIB readers.
`src/reformatters/noaa/gefs/gefs_config_models.py`	Makes `gefs_file_type` handling more precise and type-safe by enumerating simple file types and using `assert_never` for impossible branches to satisfy ty.
`src/reformatters/noaa/gefs/forecast_35_day/template_config.py`	Adjusts append-dim chunk-size computation to go through a float variable (per ty) and removes computed_field mypy ignores.
`src/reformatters/noaa/gefs/analysis/template_config.py`	Same pattern as GEFS 35-day: chunk-size calculation via an intermediate float and computed_field cleanup.
`src/reformatters/example/template_config.py`	Updates example TemplateConfig to the new computed_field style without mypy-specific ignores.
`src/reformatters/example/region_job.py`	Removes an old mypy `type-var` ignore in commented example logic.
`src/reformatters/ecmwf/ifs_ens/forecast_15_day_0_25_degree/template_config.py`	Cleans computed_field annotations and keeps TemplateConfig integration compatible with ty.
`src/reformatters/ecmwf/ifs_ens/forecast_15_day_0_25_degree/region_job.py`	Removes mypy `import-untyped` ignore for `rasterio`.
`src/reformatters/dwd/icon_eu/forecast/template_config.py`	Uses computed_field without mypy ignores for the new DWD ICON-EU forecast template.
`src/reformatters/dwd/icon_eu/forecast/region_job.py`	Drops mypy ignore for `rasterio` and cleans up a commented example `type-var` ignore in `update_template_with_results`.
`src/reformatters/contrib/uarizona/swann/analysis/template_config.py`	Cleans computed_fields for the SWANN analysis TemplateConfig.
`src/reformatters/contrib/uarizona/swann/analysis/region_job.py`	Removes mypy import ignore on `rasterio` and updates an unused-parameter name to comply with linting; note: still uses `from rasterio import rasterio`, which is likely an incorrect import form and should be `import rasterio`.
`src/reformatters/contrib/noaa/ndvi_cdr/analysis/template_config.py`	Removes mypy-specific computed_field ignores for the NDVI CDR analysis template.
`src/reformatters/contrib/noaa/ndvi_cdr/analysis/region_job.py`	Drops mypy `import-untyped` on `rasterio` and renames an unused parameter with an ARG002 suppression.
`src/reformatters/contrib/noaa/ndvi_cdr/analysis/quality_flags.py`	Removes a `no-any-return` ignore now that return types are precise.
`src/reformatters/contrib/nasa/smap/level3_36km_v9/template_config.py`	Applies the same computed_field cleanup and uses ty-friendly typing for coords and data_vars.
`src/reformatters/contrib/nasa/smap/level3_36km_v9/region_job.py`	Drops mypy `import-untyped` from `rasterio` and marks an unused parameter appropriately.
`src/reformatters/common/zarr.py`	Adds `zarr.core.sync` import explicitly for `sync_to_store`, aligning with ty’s module-resolution expectations.
`src/reformatters/common/validation.py`	Adds explicit `zarr.core.sync` / `zarr.storage` imports and keeps validation helpers typed in a way that ty can understand.
`src/reformatters/common/update_progress_tracker.py`	Removes the mypy ignore on `fsspec`, imports `fsspec.implementations.local`, and uses it for a precise `LocalFileSystem` type check.
`src/reformatters/common/template_utils.py`	Drops mypy `no-untyped-call` ignores for `dask.array.full` and adds explicit zarr submodule imports for ty.
`src/reformatters/common/template_config.py`	Cleans all TemplateConfig computed_fields of mypy ignores, updates `derive_coordinates` signatures for ty, and makes append-dim chunk-size computation explicitly go through a float to satisfy ty’s Timedelta-division typing.
`src/reformatters/common/storage.py`	Removes mypy import ignore on `fsspec`, imports zarr submodules explicitly, and keeps `StorageConfig.version` as a computed_field without mypy-specific suppression.
`src/reformatters/common/region_job.py`	Removes a `type-var` ignore in `update_template_with_results`, adds a ty-ignore for the `max(..., default=None)` call, and explicitly annotates an xarray Dataset slice to work around stub issues.
`src/reformatters/common/kubernetes.py`	Drops the mypy import-untyped ignore on the Kubernetes client/config import.
`src/reformatters/common/interpolation.py`	Removes numba decorator type-ignore and introduces a ty-ignore on `prange` iteration, keeping the numba-accelerated interpolation logic intact.
`src/reformatters/common/dynamical_dataset.py`	Adds an explicit `sentry_sdk.crons` import and cleans computed_fields for ty compatibility.
`src/reformatters/common/deaccumulation.py`	Similar to interpolation: cleans numba decorator ignore and adds a ty-ignore on `prange`, preserving deaccumulation behavior.
`src/reformatters/common/config_models.py`	Reworks `codecs_to_dicts` to return only dicts (instead of sometimes codecs) and makes its input optional, aligning Encoding.filters with ty’s expectations.
`src/reformatters/common/binary_rounding.py`	Removes numba decorator type-ignore and adds a `prange` ty-ignore while keeping rounding logic unchanged.

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src/reformatters/contrib/uarizona/swann/analysis/region_job.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

JackKelly · 2026-02-02T10:12:48Z

Love this 🙂

aldenks · 2026-02-02T16:25:29Z

@JackKelly it checks the whole repo in 1.9s! (mypy is 18s). Im going to wait to update and merge it until #406 is on main to not create merge conflicts for you

aldenks commented Jan 30, 2026

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aldenks force-pushed the claude/migrate-mypy-to-ty-FfWTU branch from 86c253d to 2ad3ff0 Compare January 30, 2026 15:13

claude and others added 3 commits January 30, 2026 16:27

cleanup

6e4b276

ty: error-on-warning and fix or ignore all

7cc985b

aldenks force-pushed the claude/migrate-mypy-to-ty-FfWTU branch from b949cb8 to 7cc985b Compare January 30, 2026 21:47

aldenks and others added 4 commits January 30, 2026 21:23

Fix ty type errors for zarr submodule imports (#405)

0f1abb8

Remove @OverRide decorators

736ad3c

Remove typing.override decorators since they're not used consistently throughout the codebase. Add noqa: ARG002 comments for unused method arguments that are required by the parent class interface. https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

Format code

9db30df

https://claude.ai/code/session_01RTS6T1SJHLNr4u6vinbqVg

aldenks requested a review from Copilot January 31, 2026 15:29

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src/reformatters/contrib/uarizona/swann/analysis/region_job.py Outdated Show resolved Hide resolved

Update region_job.py

2965d8a

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

aldenks mentioned this pull request Feb 3, 2026

What should ArkVex work on? #411

Closed

aldenks added 2 commits February 3, 2026 15:35

Merge branch 'main' into claude/migrate-mypy-to-ty-FfWTU

fc670e0

sort imports

3847f2a

aldenks marked this pull request as ready for review February 3, 2026 20:37

self review

6e200da

aldenks enabled auto-merge (squash) February 3, 2026 20:51

aldenks merged commit 4697ffa into main Feb 3, 2026
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aldenks deleted the claude/migrate-mypy-to-ty-FfWTU branch February 3, 2026 20:54

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Replace mypy with ty for type checking#400

Replace mypy with ty for type checking#400
aldenks merged 11 commits intomainfrom
claude/migrate-mypy-to-ty-FfWTU

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		# xarray's __getitem__ with a list returns Dataset, but ty stubs say DataArray
		ds: xr.Dataset = self.template_ds[[v.name for v in self.data_vars]] # type: ignore[assignment]

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aldenks commented Jan 30, 2026

Summary

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Configuration & Setup

CI/CD & Documentation

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Type Checking Configuration

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