MNT: Add provisional get_backend(resolve=False) flag

timhoffm · timhoffm · commit 9640a9520dd8 · 2024-10-29T17:37:56.000+01:00
The default is `resolve=True` for now, so that this introduction is completely backward-compatible. The provisional introduction anticipates planned changes for the backend resolution (#26406 (comment)). If all plays out as intended, this prolongs the range of releases for the migration: If we start deprecating `rcParams._get("backend")` say in 3.11, people can immediately switch to `get_backend(resolve=False)` and their code still runs on 3.10 without version gating. The worst that can happen is that the introduced flag was not helpful and we remove it again, which is easy because it's provisional.
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -1296,7 +1296,7 @@ def use(backend, *, force=True):
     rcParams['backend'] = os.environ.get('MPLBACKEND')
 
 
-def get_backend(*, resolve: bool = True):
+def get_backend(*, resolve=True):
     """
     Return the name of the current backend.
 
diff --git a/lib/matplotlib/tests/test_rcparams.py b/lib/matplotlib/tests/test_rcparams.py
@@ -554,7 +554,7 @@ def test_backend_fallback_headful(tmp_path):
          # Check that access on another instance does not resolve the sentinel.
          "assert mpl.RcParams({'backend': sentinel})['backend'] == sentinel; "
          "assert mpl.rcParams._get('backend') == sentinel; "
-         "assert matplotlib.get_backend(resolve=False) is None; "
+         "assert mpl.get_backend(resolve=False) is None; "
          "import matplotlib.pyplot; "
          "print(matplotlib.get_backend())"],
         env=env, text=True, check=True, capture_output=True).stdout
