Add runtime type checking in CI tests

.github/workflows/ci-additional.yaml

@@ -80,6 +80,47 @@ jobs:
           # `xarray/tests/__init__.py`.
           python -m pytest --doctest-modules xarray --ignore xarray/tests -Werror
 
+  beartype:
+    name: beartype
+    runs-on: "ubuntu-latest"
+    needs: detect-ci-trigger
+    defaults:
+      run:
+        shell: bash -l {0}
+    env:
+      CONDA_ENV_FILE: ci/requirements/environment.yml
+      PYTHON_VERSION: "3.12"
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # Fetch all history for all branches and tags.
+
+      - name: set environment variables
+        run: |
+          echo "TODAY=$(date +'%Y-%m-%d')" >> $GITHUB_ENV
+      - name: Setup micromamba
+        uses: mamba-org/setup-micromamba@v2
+        with:
+          micromamba-version: ${{env.MICROMAMBA_VERSION}}
+          environment-file: ${{env.CONDA_ENV_FILE}}
+          environment-name: xarray-tests
+          create-args: >-
+            python=${{env.PYTHON_VERSION}}
+          cache-environment: true
+          cache-environment-key: "${{runner.os}}-${{runner.arch}}-py${{env.PYTHON_VERSION}}-${{env.TODAY}}-${{hashFiles(env.CONDA_ENV_FILE)}}"
+      - name: Install xarray
+        run: |
+          python -m pip install --no-deps -e .
+      - name: Version info
+        run: |
+          python xarray/util/print_versions.py
+
+      - name: Run beartype
+        continue-on-error: true
+        run: |
+          python -m pytest --beartype-packages=xarray
+
   mypy:
     name: Mypy
     runs-on: "ubuntu-latest"

ci/requirements/environment.yml

@@ -38,6 +38,7 @@ dependencies:
   - pydap
   - pydap-server
   - pytest
+  - pytest-beartype
   - pytest-cov
   - pytest-env
   - pytest-xdist

pyproject.toml

@@ -41,6 +41,7 @@ dev = [
   "mypy",
   "pre-commit",
   "pytest",
+  "pytest-beartype",
   "pytest-cov",
   "pytest-env",
   "pytest-xdist",
@@ -290,6 +291,9 @@ ban-relative-imports = "all"
 [tool.pytest.ini_options]
 addopts = ["--strict-config", "--strict-markers"]
 
+[lint.pyupgrade]
+keep-runtime-typing = true
+
 # We want to forbid warnings from within xarray in our tests — instead we should
 # fix our own code, or mark the test itself as expecting a warning. So this:
 # - Converts any warning from xarray into an error

xarray/core/dataset.py

@@ -468,7 +468,7 @@ def merge_data_and_coords(data_vars: DataVars, coords) -> _MergeResult:
     )
 
 
-class DataVariables(Mapping[Any, "DataArray"]):
+class DataVariables(Mapping[Any, "xarray.DataArray"]):
     __slots__ = ("_dataset",)
 
     def __init__(self, dataset: Dataset):
@@ -550,7 +550,7 @@ class Dataset(
     DataWithCoords,
     DatasetAggregations,
     DatasetArithmetic,
-    Mapping[Hashable, "DataArray"],
+    Mapping[Hashable, "xarray.DataArray"],
 ):
     """A multi-dimensional, in memory, array database.