Fix type hints for Python versions < 3.10

.github/workflows/run-tests.yml

@@ -21,6 +21,7 @@ on:
   push:
     branches:
       - main
+      - mypy-python-version
   # run the test only if the PR is to main
   # turn it on if required
   #pull_request:

esmvalcore/_recipe/from_datasets.py

@@ -6,7 +6,7 @@
 import re
 from copy import deepcopy
 from functools import partial
-from typing import TYPE_CHECKING, Any, Iterable, Mapping, Sequence
+from typing import TYPE_CHECKING, Any, Dict, Iterable, Mapping, Sequence
 
 from nested_lookup import nested_delete
 
@@ -17,8 +17,8 @@
 
 logger = logging.getLogger(__name__)
 
-Recipe = dict[str, Any]
-Facets = dict[str, Any]
+Recipe = Dict[str, Any]
+Facets = Dict[str, Any]
 
 
 def _datasets_to_raw_recipe(datasets: Iterable[Dataset]) -> Recipe:

esmvalcore/dataset.py

@@ -9,7 +9,7 @@
 from copy import deepcopy
 from fnmatch import fnmatchcase
 from pathlib import Path
-from typing import Any, Iterator, Sequence
+from typing import Any, Iterator, Sequence, Union
 
 from iris.cube import Cube
 
@@ -39,7 +39,7 @@
 
 logger = logging.getLogger(__name__)
 
-File = esgf.ESGFFile | local.LocalFile
+File = Union[esgf.ESGFFile, local.LocalFile]
 
 
 def _augment(base: dict, update: dict):

setup.cfg

@@ -36,6 +36,7 @@ include_trailing_comma = true
 
 [mypy]
 # see mypy.readthedocs.io/en/stable/command_line.html
+python_version = 3.9
 ignore_missing_imports = True
 files = esmvalcore, tests