Allow passing a tuple of sources (#421)

Allow passing a tuple of sources, while modernizing type annotations for a small module.


* Allow passing tuple of sources, while modernizing type annotations and expanding docstring

Signed-off-by: F.N. Claessen <felix@seita.nl>

* flake8

Signed-off-by: F.N. Claessen <felix@seita.nl>

* Changelog entry

Signed-off-by: F.N. Claessen <felix@seita.nl>

* Refactor import

Signed-off-by: F.N. Claessen <felix@seita.nl>

documentation/changelog.rst

@@ -17,6 +17,7 @@ Infrastructure / Support
 ----------------------
 * Unit conversion prefers shorter units in general [see `PR #415 <http://www.github.com/FlexMeasures/flexmeasures/pull/415>`_]
 * Shorter CI builds in Github Actions by caching Python environment [see `PR #361 <http://www.github.com/FlexMeasures/flexmeasures/pull/361>`_]
+* Allow to filter data by source using a tuple instead of a list [see `PR #421 <http://www.github.com/FlexMeasures/flexmeasures/pull/421>`_]
 
 
 v0.9.3 | April 15, 2022

flexmeasures/data/models/parsing_utils.py

@@ -1,4 +1,6 @@
-from typing import Optional, Union, List
+from __future__ import annotations
+
+from collections.abc import Sequence
 
 from flask import current_app
 from flexmeasures.data import db
@@ -7,18 +9,26 @@
 
 
 def parse_source_arg(
-    source: Optional[
-        Union[DataSource, List[DataSource], int, List[int], str, List[str]]
-    ]
-) -> Optional[List[DataSource]]:
-    """Parse the "source" argument by looking up DataSources corresponding to any given ids or names."""
+    source: DataSource
+    | int
+    | str
+    | Sequence[DataSource]
+    | Sequence[int]
+    | Sequence[str]
+    | None,
+) -> list[DataSource] | None:
+    """Parse the "source" argument by looking up DataSources corresponding to any given ids or names.
+
+    Passes None as is (i.e. no source argument is given).
+    Accepts ids and names as list or tuples, always converting them to a list.
+    """
     if source is None:
         return source
-    if not isinstance(source, list):
+    if isinstance(source, (DataSource, str, int)):
         sources = [source]
     else:
         sources = source
-    parsed_sources: List[DataSource] = []
+    parsed_sources: list[DataSource] = []
     for source in sources:
         if isinstance(source, int):
             parsed_source = (