Bug 1799717: Adding a try/catch block in the test to exempt some known possible failures.r=jari

Differential Revision: https://phabricator.services.mozilla.com/D210174

dom/cache/test/marionette/test_caches_delete_cleanup_after_shutdown.py

@@ -3,6 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
+import time
 
 from marionette_driver import Wait
 from marionette_harness import MarionetteTestCase
@@ -77,19 +78,15 @@ class CachesDeleteCleanupAtShutdownTestCase(MarionetteTestCase):
             script_args=(CACHE_ID,),
         )
 
-    def countBodies(self):
+    # asynchronously iterating over body files could be challenging as firefox
-        profile = self.marionette.instance.profile.profile
+    # might be doing some cleanup while we are iterating over it's morgue dir.
-        originDir = (
+    # It's expected for this helper to throw FileNotFoundError exception in
-            self.marionette.absolute_url("")[:-1].replace(":", "+").replace("/", "+")
+    # such cases.
-        )
+    def fallibleCountBodies(self, morgueDir):
-        morgueDir = f"{profile}/storage/default/{originDir}/cache/morgue"
-        print("morgueDir path = ", morgueDir)
-
-        bodyCount = -1
-        if os.path.exists(morgueDir):
         bodyCount = 0
         for elem in os.listdir(morgueDir):
             absPathElem = os.path.join(morgueDir, elem)
+
             if os.path.isdir(absPathElem):
                 bodyCount += sum(
                     1
@@ -98,6 +95,27 @@ class CachesDeleteCleanupAtShutdownTestCase(MarionetteTestCase):
                 )
         return bodyCount
 
+    def countBodies(self):
+        profile = self.marionette.instance.profile.profile
+        originDir = (
+            self.marionette.absolute_url("")[:-1].replace(":", "+").replace("/", "+")
+        )
+
+        morgueDir = f"{profile}/storage/default/{originDir}/cache/morgue"
+        print("morgueDir path = ", morgueDir)
+
+        if not os.path.exists(morgueDir):
+            print("morgue directory does not exists.")
+            return -1
+
+        while True:
+            try:
+                return self.fallibleCountBodies(morgueDir)
+            except FileNotFoundError:
+                # we probably just got in the period when firefox was cleaning up.
+                # retry...
+                time.sleep(0.5)
+
     def ensureCleanDirectory(self):
         orphanedBodiesCount = self.countBodies()
         return orphanedBodiesCount <= 0