Fix TargetPlatformPresentationReconciler: stop scanning past damage end by vogella · Pull Request #2284 · eclipse-pde/eclipse.pde

vogella · 2026-04-06T10:41:29Z

Summary

Fixes #2283 (also related to eclipse-platform/eclipse.platform.ui#2276).

TargetPlatformPresentationReconciler.createPresentation() overrides the default
PresentationReconciler behaviour to always scan from offset 0. This is
necessary to correctly handle multi-line XML comment rules ():
without the full context from the start of the document, a comment that opened
before the damaged region would not be recognised.

However, the scan was running all the way to document.getLength() even though
the TextPresentation returned is constructed with the damage region as its
extent — meaning any style ranges added for content after the damage end are
silently discarded. This results in O(document length) work on the UI thread
for every keystroke, causing noticeable freezes in large .target files.

Changes

TargetPlatformPresentationReconciler — change the upper bound of
TextUtilities.computePartitioning() from document.getLength() to
damage.getOffset() + damage.getLength(). Scanning still starts at offset 0
(multi-line rule correctness is preserved); it just stops where it would have
discarded results anyway.
MANIFEST.MF (genericeditor.extension) — declare
org.eclipse.pde.genericeditor.extension.tests as a friend of the
reconciler.presentation package so the new tests can subclass the reconciler.
TargetPlatformPresentationReconcilerTest — new test class covering:
- simple document, full damage
- damage covering only the end of the document
- multi-line comment before the damage region
- damage region inside a multi-line comment

Known limitation

For edits very close to the end of a large file the gain is small (the damage
end ≈ the document end). A more thorough fix — e.g. caching scanner state
between edits, using a real IDocumentPartitioner for comments, or moving
reconciliation off the UI thread — is left for a follow-up.

Test plan

Compiles cleanly (mvn clean compile on the two affected bundles)
TargetPlatformPresentationReconcilerTest passes in a running Eclipse test environment
All existing AllTargetEditorTests continue to pass

🤖 Generated with Claude Code

eclipse-pde-bot · 2026-04-06T10:49:43Z

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

ui/org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF
ui/org.eclipse.pde.genericeditor.extension.tests/pom.xml

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 0fa2556683520335d6b82feebcfa16423c685d74 Mon Sep 17 00:00:00 2001
From: Eclipse PDE Bot <pde-bot@eclipse.org>
Date: Mon, 6 Apr 2026 10:58:02 +0000
Subject: [PATCH] Version bump(s) for 4.40 stream


diff --git a/ui/org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF b/ui/org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF
index 035112ee37..e40d9d7d57 100644
--- a/ui/org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF
+++ b/ui/org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: Tests for Generic Target Platform Editor
 Bundle-SymbolicName: org.eclipse.pde.genericeditor.extension.tests
-Bundle-Version: 1.3.200.qualifier
+Bundle-Version: 1.3.300.qualifier
 Bundle-Vendor: Eclipse.org
 Bundle-RequiredExecutionEnvironment: JavaSE-21
 Require-Bundle: org.eclipse.core.runtime;bundle-version="[3.29.0,4.0.0)",
diff --git a/ui/org.eclipse.pde.genericeditor.extension.tests/pom.xml b/ui/org.eclipse.pde.genericeditor.extension.tests/pom.xml
index 8b3cafceec..4f98690f41 100644
--- a/ui/org.eclipse.pde.genericeditor.extension.tests/pom.xml
+++ b/ui/org.eclipse.pde.genericeditor.extension.tests/pom.xml
@@ -18,7 +18,7 @@
     <relativePath>../../</relativePath>
   </parent>
   <artifactId>org.eclipse.pde.genericeditor.extension.tests</artifactId>
-  <version>1.3.200-SNAPSHOT</version>
+  <version>1.3.300-SNAPSHOT</version>
   <packaging>eclipse-test-plugin</packaging>
 
   <properties>
-- 
2.53.0

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

github-actions · 2026-04-06T11:36:58Z

Test Results

150 files + 3 150 suites +3 36m 50s ⏱️ + 1m 29s
3 501 tests + 4 3 446 ✅ + 3 54 💤 ±0 1 ❌ +1
9 324 runs +12 9 193 ✅ +11 130 💤 ±0 1 ❌ +1

For more details on these failures, see this check.

Results for commit 58c2c98. ± Comparison against base commit 50600c6.

♻️ This comment has been updated with latest results.

Copilot

Pull request overview

Improves the Generic Target Platform Editor’s syntax highlighting reconciler performance by avoiding unnecessary full-document partition scanning while preserving correctness for multi-line XML comment rules.

Changes:

Limit TargetPlatformPresentationReconciler partition scan length to the end of the damage region (still starting at offset 0).
Export reconciler.presentation as a “friend” package to enable test subclassing.
Add a new JUnit test class and wire it into the existing test suite; bump test bundle versions accordingly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`.../TargetPlatformPresentationReconciler.java`	Stops partition scanning at damage end instead of document end to reduce UI-thread work.
`.../org.eclipse.pde.genericeditor.extension/META-INF/MANIFEST.MF`	Marks `reconciler.presentation` as `x-friends` for the test bundle.
`.../TargetPlatformPresentationReconcilerTest.java`	Adds new tests for reconciler behavior across damage/comment scenarios.
`.../AllTargetEditorTests.java`	Includes the new reconciler test class in the suite.
`.../org.eclipse.pde.genericeditor.extension.tests/pom.xml`	Bumps test bundle Maven version.
`.../org.eclipse.pde.genericeditor.extension.tests/META-INF/MANIFEST.MF`	Bumps OSGi bundle version.

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Copilot · 2026-04-15T13:00:33Z

+				int scanEnd = damage.getOffset() + damage.getLength();
 				ITypedRegion[] regions = TextUtilities.computePartitioning(document, getDocumentPartitioning(), 0,
-						document.getLength(), false);
+						scanEnd, false);


scanEnd is derived from damage.getOffset() + damage.getLength() and is passed to TextUtilities.computePartitioning(...) as the length parameter. If the provided damage region ever extends past the current document.getLength() (e.g., due to a stale damage region during rapid edits), computePartitioning will throw BadLocationException and this method returns null, potentially breaking syntax highlighting. Consider clamping the computed scan length to document.getLength() (and generally ensuring it is within valid bounds) before calling computePartitioning.

Copilot · 2026-04-15T13:00:33Z

+	@Test
+	public void testCreatePresentationReturnsNonNullForSimpleDocument() {
+		TestableReconciler reconciler = new TestableReconciler();
+		String content = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" //$NON-NLS-1$
+				+ "<target name=\"test\">\n" //$NON-NLS-1$
+				+ "  <locations/>\n" //$NON-NLS-1$
+				+ "</target>\n"; //$NON-NLS-1$
+		IDocument document = new Document(content);
+		IRegion damage = new Region(0, content.length());
+
+		TextPresentation presentation = reconciler.createPresentation(document, damage);
+
+		assertNotNull("Expected a non-null TextPresentation for a simple document", presentation); //$NON-NLS-1$
+	}


These tests only assert that createPresentation(...) returns a non-null TextPresentation, which would still pass even if the reconciler kept scanning to the end of the document (the original regression) or produced incorrect styling. To make this a meaningful regression test for the performance fix, consider installing a custom IDocumentPartitioner (or similar hook) on the IDocument that records the offset/length requested by TextUtilities.computePartitioning, then assert that the computed length matches damage.getOffset() + damage.getLength() rather than document.getLength().

The reconciler always scanned the full document (offset 0 to document.getLength()) on every keystroke to ensure multi-line XML comment rules are honoured. While scanning from offset 0 is required for correctness, scanning *past* the damage end is wasted work because the returned TextPresentation is bounded by the damage region and silently discards any style ranges beyond it. Change the upper bound of TextUtilities.computePartitioning() from document.getLength() to damage.getOffset() + damage.getLength(). This avoids scanning content whose results would be thrown away, while preserving the full-context scan from offset 0 that multi-line rules require. Add TargetPlatformPresentationReconcilerTest to verify correctness for the common cases: simple documents, partial damage regions, multi-line comments before the damage, and damage inside a multi-line comment. Fixes: eclipse-pde#2283 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

vogella force-pushed the full-qualified-access branch from ad4c2fd to e08d95d Compare April 6, 2026 10:55

vogella force-pushed the full-qualified-access branch from 30a7061 to c91f39e Compare April 6, 2026 19:26

vogella marked this pull request as ready for review April 8, 2026 07:25

vogella force-pushed the full-qualified-access branch from c91f39e to a2b3bb3 Compare April 14, 2026 17:19

vogella requested a review from Copilot April 15, 2026 12:56

Copilot started reviewing on behalf of vogella April 15, 2026 12:56 View session

Copilot AI reviewed Apr 15, 2026

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vogella force-pushed the full-qualified-access branch from a2b3bb3 to 31f0806 Compare April 15, 2026 13:27

vogella and others added 2 commits April 15, 2026 15:27

Version bump(s) for 4.40 stream

58c2c98

vogella force-pushed the full-qualified-access branch from 31f0806 to 58c2c98 Compare April 15, 2026 13:27

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Fix TargetPlatformPresentationReconciler: stop scanning past damage end#2284

Fix TargetPlatformPresentationReconciler: stop scanning past damage end#2284
vogella wants to merge 2 commits intoeclipse-pde:masterfrom
vogella:full-qualified-access

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vogella commented Apr 6, 2026

Summary

Changes

Known limitation

Test plan

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