Address timeout issues directly

Author: richardsheridan

lib/matplotlib/tests/test_backend_tk.py

@@ -1,5 +1,6 @@
-import threading
-import time
+import os
+import subprocess
+import sys
 import tkinter
 
 import numpy as np
@@ -56,25 +57,44 @@ def legitmate_quit():
 
 
 @pytest.mark.backend('TkAgg', skip_on_importerror=True)
+@pytest.mark.flaky(reruns=3)
 def test_figuremanager_cleans_own_mainloop():
-    root = tkinter.Tk()
-    plt.plot([1, 2, 3], [1, 2, 5])
-    can_detect_mainloop = False
-    thread_died_before_quit = True
-
-    def target():
-        nonlocal can_detect_mainloop
-        nonlocal thread_died_before_quit
-        from matplotlib.cbook import _get_running_interactive_framework
-
-        time.sleep(0.1)  # should poll for mainloop being up
-        can_detect_mainloop = 'tk' == _get_running_interactive_framework()
-        plt.close()
-        time.sleep(0.1)  # should poll for mainloop going down
-        root.quit()
-        thread_died_before_quit = False
-
-    threading.Thread(target=target, daemon=True).start()
-    plt.show(block=True)
-    assert can_detect_mainloop
-    assert thread_died_before_quit
+    script = '''
+import tkinter
+import time
+import matplotlib.pyplot as plt
+import threading
+from matplotlib.cbook import _get_running_interactive_framework
+
+root = tkinter.Tk()
+plt.plot([1, 2, 3], [1, 2, 5])
+
+def target():
+    while not 'tk' == _get_running_interactive_framework():
+        time.sleep(.01)
+    plt.close()
+    if show_finished_event.wait():
+        print('success')
+        
+show_finished_event = threading.Event()
+thread = threading.Thread(target=target, daemon=True)
+thread.start()
+plt.show(block=True)  # testing if this function hangs
+show_finished_event.set()
+thread.join()
+
+'''
+    try:
+        proc = subprocess.run(
+            [sys.executable, "-c", script],
+            env={**os.environ, "MPLBACKEND": "TkAgg", "SOURCE_DATE_EPOCH": "0"},
+            timeout=10,
+            stdout=subprocess.PIPE,
+            universal_newlines=True,
+            check=True
+        )
+    except subprocess.TimeoutExpired:
+        pytest.fail("Most likely plot.show(block=True) hung")
+    except subprocess.CalledProcessError:
+        pytest.fail("Subprocess failed to test intended behavior")
+    assert proc.stdout.count("success") == 1