Backport PR #23057 and #23106 (#23113)

tacaswell · anntzer · web-flow · commit c5a24ff28f67 · 2022-06-02T13:02:03.000+02:00
* Backport PR #23057: FIX: ensure switching the backend installs repl hook Merge pull request #23057 from tacaswell/fix_pylab (cherry picked from commit b31c5ae) * Merge pull request #23106 from anntzer/tpi MNT: Reuse subprocess_run_helper in test_pylab_integration. (cherry picked from commit 51624b6) * TST: Adjust to state tracking on 3.5.x branch The implementation of tracking if the repl displayhook is installed changed on main. Adjust the backported test to work with the old way. Co-authored-by: Antony Lee <anntzer.lee@gmail.com>
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -215,12 +215,6 @@ def _get_backend_mod():
         # will (re)import pyplot and then call switch_backend if we need to
         # resolve the auto sentinel)
         switch_backend(dict.__getitem__(rcParams, "backend"))
-        # Just to be safe.  Interactive mode can be turned on without calling
-        # `plt.ion()` so register it again here.  This is safe because multiple
-        # calls to `install_repl_displayhook` are no-ops and the registered
-        # function respects `mpl.is_interactive()` to determine if it should
-        # trigger a draw.
-        install_repl_displayhook()
     return _backend_mod
 
 
@@ -311,6 +305,10 @@ class backend_mod(matplotlib.backend_bases._Backend):
     # See https://github.com/matplotlib/matplotlib/issues/6092
     matplotlib.backends.backend = newbackend
 
+    # make sure the repl display hook is installed in case we become
+    # interactive
+    install_repl_displayhook()
+
 
 def _warn_if_gui_out_of_main_thread():
     if (_get_required_interactive_framework(_get_backend_mod())
diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
@@ -335,3 +335,17 @@ def test_fallback_position():
     axtest = plt.axes([0.2, 0.2, 0.5, 0.5], position=[0.1, 0.1, 0.8, 0.8])
     np.testing.assert_allclose(axtest.bbox.get_points(),
                                axref.bbox.get_points())
+
+
+def test_pylab_integration():
+    IPython = pytest.importorskip("IPython")
+    mpl.testing.subprocess_run_helper(
+        IPython.start_ipython,
+        "--pylab",
+        "-c",
+        ";".join((
+            "import matplotlib.pyplot as plt",
+            "assert plt._IP_REGISTERED is not None",
+        )),
+        timeout=60,
+    )
