typing annotations

.pre-commit-config.yaml

@@ -28,3 +28,21 @@ repos:
       rev: v5.6.4
       hooks:
       -   id: isort
+
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v0.910-1
+    hooks:
+      - id: mypy
+        #  `asv_bench` are copied from setup.cfg.
+        # `_typed_ops.py` is added since otherwise mypy will complain (but notably only in pre-commit)
+        exclude: "asv_bench"
+        additional_dependencies: [
+            # Type stubs
+            types-python-dateutil,
+            types-pkg_resources,
+            types-PyYAML,
+            types-pytz,
+            typing-extensions==3.10.0.0,
+            # Dependencies that are typed
+            numpy,
+          ]

ci/requirements/climpred-dev.yml

@@ -30,13 +30,14 @@ dependencies:
   - black==19.10b0
   - coveralls
   - flake8
-  #- importlib_metadata
+  - mypy
   - isort
   - pre-commit
   - pylint
   - pytest
   - pytest-cov
   - pytest-sugar
+  - mypy_extensions
   # Performance
   - bottleneck
   - numba

ci/requirements/docs.yml

@@ -7,6 +7,7 @@ dependencies:
   - importlib_metadata
   - matplotlib-base
   - nbsphinx
+  - mypy_extensions
   - nc-time-axis
   - netcdf4
   - sphinx

ci/requirements/docs_notebooks.yml

@@ -18,6 +18,7 @@ dependencies:
   - sphinxcontrib-napoleon
   - sphinx_rtd_theme
   - sphinx-copybutton
+  - mypy_extensions
   - toolz
   - xarray>=0.16.1
   - esmtools>=1.1.3

ci/requirements/maximum-tests.yml

@@ -17,6 +17,7 @@ dependencies:
   - pytest
   - pytest-cov
   - pytest-xdist
+  - mypy_extensions
   - scipy
   - xarray>=0.16.1
   - xesmf

ci/requirements/minimum-tests.yml

@@ -16,6 +16,7 @@ dependencies:
   - scipy
   - xarray>=0.16.1
   - xskillscore>=0.0.18
+  - mypy_extensions
   - pip:
     - pytest-lazy-fixture
     - -e ../..

climpred/checks.py

@@ -307,7 +307,10 @@ def warn_if_chunking_would_increase_performance(ds, crit_size_in_MB=100):
             )
 
 
-def _check_valid_reference(reference):
+from typing import List, Optional, Union
+
+
+def _check_valid_reference(reference: Optional[Union[List[str], str]]) -> List:
     """Enforce reference as list and check for valid entries."""
     if reference is None:
         reference = []