ENH: When using another plotting backend, minimize pre-processing (pandas-dev#28647)

Author: jsignell

pandas/plotting/_core.py

@@ -776,6 +776,11 @@ def __call__(self, *args, **kwargs):
         )
 
         kind = self._kind_aliases.get(kind, kind)
+
+        # when using another backend, get out of the way
+        if plot_backend.__name__ != "pandas.plotting._matplotlib":
+            return plot_backend.plot(self._parent, x=x, y=y, kind=kind, **kwargs)
+
         if kind not in self._all_kinds:
             raise ValueError("{} is not a valid plot kind".format(kind))
 

pandas/tests/plotting/test_backend.py

@@ -94,3 +94,11 @@ def test_setting_backend_without_plot_raises():
 def test_no_matplotlib_ok():
     with pytest.raises(ImportError):
         pandas.plotting._core._get_plot_backend("matplotlib")
+
+
+def test_extra_kinds_ok(monkeypatch, restore_backend):
+    # https://github.com/pandas-dev/pandas/pull/28647
+    monkeypatch.setitem(sys.modules, "pandas_dummy_backend", dummy_backend)
+    pandas.set_option("plotting.backend", "pandas_dummy_backend")
+    df = pandas.DataFrame({"A": [1, 2, 3]})
+    df.plot(kind="not a real kind")