Merging upstream version 127.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/browser/actors/ContextMenuChild.sys.mjs b/browser/actors/ContextMenuChild.sys.mjs
index 5ecbcb22e9..2b98bea65e 100644
--- a/browser/actors/ContextMenuChild.sys.mjs
+++ b/browser/actors/ContextMenuChild.sys.mjs
@@ -535,6 +535,23 @@ export class ContextMenuChild extends JSWindowActorChild {
     }
 
     let doc = aEvent.composedTarget.ownerDocument;
+    if (!doc && Cu.isInAutomation) {
+      // doc has been observed to be null for many years, causing intermittent
+      // test failures all over the place (bug 1478596). The rate of failures
+      // is too low to debug locally, but frequent enough to be a nuisance.
+      // TODO bug 1478596: use these diagnostic logs to resolve the bug.
+      dump(
+        `doc is unexpectedly null (bug 1478596), composedTarget=${aEvent.composedTarget}\n`
+      );
+      // A potential fix is to fall back to aEvent.target.ownerDocument, per
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=1478596#c1
+      // Let's print potentially viable alternatives to see what we should use.
+      for (let k of ["target", "originalTarget", "explicitOriginalTarget"]) {
+        dump(
+          ` Alternative: ${k}=${aEvent[k]} and its doc=${aEvent[k]?.ownerDocument}\n`
+        );
+      }
+    }
     let {
       mozDocumentURIIfNotForErrorPages: docLocation,
       characterSet: charSet,