Don't force matplotlib backend names to be lowercase (#14475)

Carreau · web-flow · commit 6bde8f6cba9a · 2024-08-30T00:36:04.000-07:00
This is something I missed as part of moving the backend resolution to Matplotlib. Since version 3.9.0 Matplotlib handles the case-sensitivity of backend names, making them all lowercase for internal use. But since matplotlib/matplotlib#28473 uppercase letters are allowed in backend names of the form `module://soMe_moDule.sOmE_NAme`. Hence we need to not force backend names to be lowercase in IPython when passing them to Matplotlib. It is just a one line change that happens to make the code simpler, plus a new test. The Matplotlib change will be released in 3.9.1 which is due shortly, possibly today. The new test checks the Matplotlib version to know whether uppercase backend module names are allowed or not.
diff --git a/IPython/core/magics/pylab.py b/IPython/core/magics/pylab.py
@@ -100,7 +100,7 @@ def matplotlib(self, line=''):
                 % _list_matplotlib_backends_and_gui_loops()
             )
         else:
-            gui, backend = self.shell.enable_matplotlib(args.gui.lower() if isinstance(args.gui, str) else args.gui)
+            gui, backend = self.shell.enable_matplotlib(args.gui)
             self._show_matplotlib_backend(args.gui, backend)
 
     @skip_doctest
diff --git a/IPython/core/tests/test_pylabtools.py b/IPython/core/tests/test_pylabtools.py
@@ -258,6 +258,29 @@ def test_qt_gtk(self):
         assert gui == "qt"
         assert s.pylab_gui_select == "qt"
 
+    @dec.skipif(not pt._matplotlib_manages_backends())
+    def test_backend_module_name_case_sensitive(self):
+        # Matplotlib backend names are case insensitive unless explicitly specified using
+        # "module://some_module.some_name" syntax which are case sensitive for mpl >= 3.9.1
+        all_lowercase = "module://matplotlib_inline.backend_inline"
+        some_uppercase = "module://matplotlib_inline.Backend_inline"
+        mpl3_9_1 = matplotlib.__version_info__ >= (3, 9, 1)
+
+        s = self.Shell()
+        s.enable_matplotlib(all_lowercase)
+        if mpl3_9_1:
+            with pytest.raises(RuntimeError):
+                s.enable_matplotlib(some_uppercase)
+        else:
+            s.enable_matplotlib(some_uppercase)
+
+        s.run_line_magic("matplotlib", all_lowercase)
+        if mpl3_9_1:
+            with pytest.raises(RuntimeError):
+                s.run_line_magic("matplotlib", some_uppercase)
+        else:
+            s.run_line_magic("matplotlib", some_uppercase)
+
 
 def test_no_gui_backends():
     for k in ['agg', 'svg', 'pdf', 'ps']:

Original file line number	Diff line number	Diff line change
`@@ -100,7 +100,7 @@ def matplotlib(self, line=''):`
`100`	`100`	`% _list_matplotlib_backends_and_gui_loops()`
`101`	`101`	`)`
`102`	`102`	`else:`
`103`		`- gui, backend = self.shell.enable_matplotlib(args.gui.lower() if isinstance(args.gui, str) else args.gui)`
	`103`	`+ gui, backend = self.shell.enable_matplotlib(args.gui)`
`104`	`104`	`self._show_matplotlib_backend(args.gui, backend)`
`105`	`105`
`106`	`106`	`@skip_doctest`