Make required_interactive_framework required on FigureCanvas.

anntzer · anntzer · commit 2a964cc07bf4 · 2021-12-24T11:21:39.000+01:00
All FigureCanvas subclasses that inherit from FigureCanvasBase already
have that attribute (which may be None), so the getattr is redundant.
In practice, it would be extremely difficult to write a FigureCanvasLike
class that does not inherit from FigureCanvasBase, but to be safe, go
through a deprecation period.
diff --git a/doc/api/next_api_changes/deprecations/22051-AL.rst b/doc/api/next_api_changes/deprecations/22051-AL.rst
@@ -0,0 +1,4 @@
+``FigureCanvas`` without a ``required_interactive_framework`` attribute
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Support for such canvas classes is deprecated.  Note that canvas classes which
+inherit from ``FigureCanvasBase`` always have such an attribute.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1650,9 +1650,13 @@ def _fix_ipython_backend2gui(cls):
             # In case we ever move the patch to IPython and remove these APIs,
             # don't break on our side.
             return
-        rif = getattr(cls, "required_interactive_framework", None)
-        backend2gui_rif = {"qt": "qt", "gtk3": "gtk3", "gtk4": "gtk4",
-                           "wx": "wx", "macosx": "osx"}.get(rif)
+        backend2gui_rif = {
+            "qt": "qt",
+            "gtk3": "gtk3",
+            "gtk4": "gtk4",
+            "wx": "wx",
+            "macosx": "osx",
+        }.get(cls.required_interactive_framework)
         if backend2gui_rif:
             if _is_non_interactive_terminal_ipython(ip):
                 ip.enable_gui(backend2gui_rif)
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -199,8 +199,13 @@ def findobj(o=None, match=None, include_self=True):
 
 
 def _get_required_interactive_framework(backend_mod):
-    return getattr(
-        backend_mod.FigureCanvas, "required_interactive_framework", None)
+    if not hasattr(backend_mod.FigureCanvas, "required_interactive_framework"):
+        _api.warn_deprecated(
+            "3.6", name="Support for FigureCanvases without a "
+            "required_interactive_framework attribute")
+        return None
+    # Inline this once the deprecation elapses.
+    return backend_mod.FigureCanvas.required_interactive_framework
 
 
 def switch_backend(newbackend):
