Avoid the full ancestor chain walk when removing elements from the Project Explorer

[vogella]

Deleting many files below a collapsed folder freezes the Project Explorer. AbstractTreeViewer.getParentElement prefers ITreePathContentProvider, so the Common Navigator answers through getParents, which compiles complete paths up to the root although only the last segment of the first path is ever used. AbstractTreeViewer.internalRemove takes that branch for every element without a widget, and with JDT enabled each ancestor level runs JavaCore.create against the workspace tree. Measured in a running IDE, deleting 2000 files ten folders deep froze the UI for 19 s; with this change the same removal is not measurable and no freeze is logged.

CommonViewer now asks getParent first and falls back to the inherited behaviour when it returns null, which confines the change to the Common Navigator. For that to be correct, getParent had to honour pipelined overrides: it resolved overriding extensions up front and called the override's plain getParent, so getPipelinedParent never ran and the pipelining code in getParent was unreachable. It now reuses findParents, the per-level routine getParents already uses, so both lookups agree. Two tests pin this: one that the override's getPipelinedParent is consulted, one that removing an unexpanded element computes exactly one parent.

[github-actions]

Test Results

   858 files  ±0     858 suites  ±0   45m 58s ⏱️ - 12m 15s
 8 218 tests +2   7 975 ✅ +2  243 💤 ±0  0 ❌ ±0 
20 556 runs  +6  19 886 ✅ +6  670 💤 ±0  0 ❌ ±0 

Results for commit 14e9435. ± Comparison against base commit a680fa8.

♻️ This comment has been updated with latest results.

[eclipse-platform-bot]

This pull request changes some projects for the first time in this development cycle.
Therefore the following files need a version increment:

bundles/org.eclipse.ui.navigator/META-INF/MANIFEST.MF

An additional commit containing all the necessary changes was pushed to the top of this PR's branch. To obtain these changes (for example if you want to push more changes) either fetch from your fork or apply the git patch.

Git patch

From 502eb818d56ad93e2c65144528ad9250920c1561 Mon Sep 17 00:00:00 2001
From: Eclipse Platform Bot <platform-bot@eclipse.org>
Date: Mon, 31 Aug 2026 12:14:12 +0000
Subject: [PATCH] Version bump(s) for 4.42 stream


diff --git a/bundles/org.eclipse.ui.navigator/META-INF/MANIFEST.MF b/bundles/org.eclipse.ui.navigator/META-INF/MANIFEST.MF
index 1663ec6e36..0036dd7e70 100644
--- a/bundles/org.eclipse.ui.navigator/META-INF/MANIFEST.MF
+++ b/bundles/org.eclipse.ui.navigator/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %Plugin.name
 Bundle-SymbolicName: org.eclipse.ui.navigator; singleton:=true
-Bundle-Version: 3.14.200.qualifier
+Bundle-Version: 3.14.300.qualifier
 Bundle-Activator: org.eclipse.ui.internal.navigator.NavigatorPlugin
 Bundle-Vendor: %Plugin.providerName
 Bundle-Localization: plugin
-- 
2.55.0

Further information are available in Common Build Issues - Missing version increments.