[orca] Structural Navigation: Handle unimplemented collection interface error

[Joanmarie Diggs <joanied src gnome org>]

commit 3d2f65ad07521296590d0ec5a95d693e8e298471
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Tue May 17 14:14:09 2022 +0200

    Structural Navigation: Handle unimplemented collection interface error
    
    The collection interface is something applications and toolkits get
    "for free" from AT-SPI2. However, applications/toolkits that provide
    their own implementation of AT-SPI2 (e.g. WebKitGtk) presumably need
    to also implement AtspiCollection themselves, or do something so that
    the default AT-SPI2 implementation is used. Currently, in WebKitGtk
    version 2.36, a non-implemented error occurs when querying the
    collection interface on the document. We were not handling this error,
    causing Orca to be silent when structural navigation commands were
    used. This commit handles the error. It cannot solve the missing
    implementation, however. Thus in WebKitGtk apps,  Orca will now announce
    things like "no more headings" when there are in fact headings present.
    
    See issue #244

 src/orca/structural_navigation.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
---
diff --git a/src/orca/structural_navigation.py b/src/orca/structural_navigation.py
index ba4725757..f1e36e38d 100644
--- a/src/orca/structural_navigation.py
+++ b/src/orca/structural_navigation.py
@@ -869,7 +869,17 @@ class StructuralNavigation:
         if matches:
             return matches.copy(), criteria
 
-        col = document.queryCollection()
+        try:
+            col = document.queryCollection()
+        except NotImplementedError:
+            msg = "STRUCTURAL NAVIGATION: %s does not implement collection" % document
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return [], None
+        except:
+            msg = "STRUCTURAL NAVIGATION: Exception querying collection on %s" % document
+            debug.println(debug.LEVEL_INFO, msg, True)
+            return [], None
+
         criteria = structuralNavigationObject.criteria(col, arg)
         rule = col.createMatchRule(criteria.states.raw(),
                                    criteria.matchStates,