Add test coverage for the Unified Diff display

team/bundles/org.eclipse.compare/META-INF/MANIFEST.MF

@@ -65,7 +65,8 @@ Export-Package: org.eclipse.compare;
    org.eclipse.ui,
    org.eclipse.ui.services,
    org.eclipse.ui.texteditor",
- org.eclipse.compare.unifieddiff;x-internal:=true
+ org.eclipse.compare.unifieddiff;x-internal:=true,
+ org.eclipse.compare.unifieddiff.internal;x-friends:="org.eclipse.team.tests.core"
 Require-Bundle: org.eclipse.ui;bundle-version="[3.206.0,4.0.0)",
  org.eclipse.core.resources;bundle-version="[3.4.0,4.0.0)",
  org.eclipse.jface.text;bundle-version="[3.8.0,4.0.0)",

team/bundles/org.eclipse.compare/compare/org/eclipse/compare/unifieddiff/internal/UnifiedDiffCodeMiningProvider.java

@@ -15,6 +15,12 @@
 
 import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffManager.error;
 import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffManager.isOverlay;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.countLines;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.mapOffsetToTabExpanded;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.mergeStyleRanges;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.removeLeadingNewLines;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.removeTrailingNewLines;
+import static org.eclipse.compare.unifieddiff.internal.UnifiedDiffText.replaceTabWithSpaces;
 
 import java.lang.reflect.Method;
 import java.util.ArrayList;
@@ -377,28 +383,6 @@ public UnifiedDiffLineHeaderCodeMining(Position position, ICodeMiningProvider pr
 			((MouseClickConsumer) getAction()).setCodeMining(this);
 		}
 
-		private static String removeTrailingNewLines(String str) {
-			if (str == null) {
-				return str;
-			}
-			int end = str.length();
-			while (end > 0 && (str.charAt(end - 1) == '\n' || str.charAt(end - 1) == '\r')) {
-				end--;
-			}
-			return end == str.length() ? str : str.substring(0, end);
-		}
-
-		private static String removeLeadingNewLines(String str) {
-			if (str == null) {
-				return str;
-			}
-			int start = 0;
-			while (start < str.length() && (str.charAt(start) == '\n' || str.charAt(start) == '\r')) {
-				start++;
-			}
-			return start == 0 ? str : str.substring(start);
-		}
-
 		private static final class ForegroundInfo {
 
 			final int x;
@@ -470,58 +454,6 @@ public void keyPressed(KeyEvent e) {
 				setTextEditorActionsActivated(false);
 			}
 
-			private List<StyleRange> mergeStyleRanges(List<StyleRange> backgrounds, List<StyleRange> foregrounds) {
-				if (backgrounds.isEmpty()) {
-					return foregrounds;
-				}
-				if (foregrounds.isEmpty()) {
-					return backgrounds;
-				}
-				List<StyleRange> result = new ArrayList<>();
-				int bgIdx = 0;
-				for (StyleRange fg : foregrounds) {
-					int fgStart = fg.start;
-					int fgEnd = fg.start + fg.length;
-					int pos = fgStart;
-					while (pos < fgEnd && bgIdx < backgrounds.size()) {
-						StyleRange bg = backgrounds.get(bgIdx);
-						int bgStart = bg.start;
-						int bgEnd = bg.start + bg.length;
-						if (bgEnd <= pos) {
-							bgIdx++;
-							continue;
-						}
-						if (bgStart >= fgEnd) {
-							break;
-						}
-						if (bgStart > pos) {
-							result.add(createRange(fg, pos, bgStart - pos, null));
-							pos = bgStart;
-						}
-						int overlapEnd = Math.min(bgEnd, fgEnd);
-						result.add(createRange(fg, pos, overlapEnd - pos, bg.background));
-						pos = overlapEnd;
-						if (bgEnd <= fgEnd) {
-							bgIdx++;
-						}
-					}
-					if (pos < fgEnd) {
-						result.add(createRange(fg, pos, fgEnd - pos, null));
-					}
-				}
-				return result;
-			}
-
-			private StyleRange createRange(StyleRange base, int start, int length, Color background) {
-				StyleRange r = (StyleRange) base.clone();
-				r.start = start;
-				r.length = length;
-				if (background != null) {
-					r.background = background;
-				}
-				return r;
-			}
-
 			private List<StyleRange> createDetailedDiffBackgroundRanges(UnifiedDiffLineHeaderCodeMining miningParam,
 					String txt) {
 				List<StyleRange> ranges = new ArrayList<>();
@@ -566,17 +498,6 @@ private List<StyleRange> createDetailedDiffBackgroundRanges(UnifiedDiffLineHeade
 				return ranges;
 			}
 
-			private static int mapOffsetToTabExpanded(String originalStr, int offset, int tabWidth) {
-				int tabCount = 0;
-				int limit = Math.min(offset, originalStr.length());
-				for (int i = 0; i < limit; i++) {
-					if (originalStr.charAt(i) == '\t') {
-						tabCount++;
-					}
-				}
-				return offset + tabCount * (tabWidth - 1);
-			}
-
 			private void setTextEditorActionsActivated(boolean state) {
 				IEditorPart part = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage()
 						.getActiveEditor();
@@ -729,9 +650,10 @@ public Point draw(GC gc, StyledText textWidget, Color color, int x, int y) {
 				}
 				try {
 					var rangeInfo = new RangeInfo(-1, -1, null);
-					String l = diffStr.substring(0, detailedDiffStart);
-					int fromLine = l.split("\n").length; //$NON-NLS-1$
-					int toLine = diffStr.substring(0, detailedDiffStart + detailedDiffLength).split("\n").length; //$NON-NLS-1$
+					// String#split drops trailing empty strings, so it must not be used to
+					// count lines: a prefix ending with \n starts the next line
+					int fromLine = countLines(diffStr.substring(0, detailedDiffStart));
+					int toLine = countLines(diffStr.substring(0, detailedDiffStart + detailedDiffLength));
 					if (fromLine == toLine) {
 						int starty = getYForLine(fromLine - 1, y, gc, textWidget);
 						Point start = getPositionForOffset(textWidget, gc, detailedDiffStart, diffStr, ranges,
@@ -1067,16 +989,4 @@ static RGB interpolate(RGB fg, RGB bg, double scale) {
 		}
 		return new RGB(128, 128, 128); // a gray
 	}
-
-	private static String replaceTabWithSpaces(String leftStr, int tabWidth) {
-		if (leftStr == null) {
-			return null;
-		}
-		StringBuilder sb = new StringBuilder();
-		for (int s = 0; s < tabWidth; s++) {
-			sb.append(' ');
-		}
-		String result = leftStr.replace("\t", sb); //$NON-NLS-1$
-		return result;
-	}
 }

team/bundles/org.eclipse.compare/compare/org/eclipse/compare/unifieddiff/internal/UnifiedDiffText.java

@@ -0,0 +1,157 @@
+/*******************************************************************************
+ * Copyright (c) 2026 SAP
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ * SAP - initial implementation
+ *******************************************************************************/
+package org.eclipse.compare.unifieddiff.internal;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.eclipse.swt.custom.StyleRange;
+import org.eclipse.swt.graphics.Color;
+
+/**
+ * Side-effect free text and style-range helpers used to lay out the unified
+ * diff code minings.
+ */
+public final class UnifiedDiffText {
+
+	private UnifiedDiffText() {
+	}
+
+	/**
+	 * Returns the number of lines of the given string, counting a trailing line
+	 * delimiter as starting a new (empty) line. An empty string is one line.
+	 */
+	public static int countLines(String str) {
+		if (str == null) {
+			return 0;
+		}
+		int result = 1;
+		for (int i = 0; i < str.length(); i++) {
+			if (str.charAt(i) == '\n') {
+				result++;
+			}
+		}
+		return result;
+	}
+
+	public static String removeTrailingNewLines(String str) {
+		if (str == null) {
+			return str;
+		}
+		int end = str.length();
+		while (end > 0 && (str.charAt(end - 1) == '\n' || str.charAt(end - 1) == '\r')) {
+			end--;
+		}
+		return end == str.length() ? str : str.substring(0, end);
+	}
+
+	public static String removeLeadingNewLines(String str) {
+		if (str == null) {
+			return str;
+		}
+		int start = 0;
+		while (start < str.length() && (str.charAt(start) == '\n' || str.charAt(start) == '\r')) {
+			start++;
+		}
+		return start == 0 ? str : str.substring(start);
+	}
+
+	/**
+	 * Expands every tab into {@code tabWidth} spaces. {@code GC#stringExtent} does
+	 * not account for tabs, so widths are always measured on the expanded string.
+	 */
+	public static String replaceTabWithSpaces(String str, int tabWidth) {
+		if (str == null) {
+			return null;
+		}
+		StringBuilder sb = new StringBuilder();
+		for (int s = 0; s < tabWidth; s++) {
+			sb.append(' ');
+		}
+		return str.replace("\t", sb); //$NON-NLS-1$
+	}
+
+	/**
+	 * Maps an offset in {@code originalStr} to the corresponding offset in
+	 * {@link #replaceTabWithSpaces(String, int)} of the same string.
+	 */
+	public static int mapOffsetToTabExpanded(String originalStr, int offset, int tabWidth) {
+		int tabCount = 0;
+		int limit = Math.min(offset, originalStr.length());
+		for (int i = 0; i < limit; i++) {
+			if (originalStr.charAt(i) == '\t') {
+				tabCount++;
+			}
+		}
+		return offset + tabCount * (tabWidth - 1);
+	}
+
+	/**
+	 * Overlays the detailed-diff background ranges onto the syntax coloring ranges.
+	 * Both lists must be sorted by offset and must not overlap within themselves.
+	 * The returned ranges keep the foreground styling and cover exactly the extent
+	 * of {@code foregrounds}.
+	 */
+	public static List<StyleRange> mergeStyleRanges(List<StyleRange> backgrounds, List<StyleRange> foregrounds) {
+		if (backgrounds.isEmpty()) {
+			return foregrounds;
+		}
+		if (foregrounds.isEmpty()) {
+			return backgrounds;
+		}
+		List<StyleRange> result = new ArrayList<>();
+		int bgIdx = 0;
+		for (StyleRange fg : foregrounds) {
+			int fgStart = fg.start;
+			int fgEnd = fg.start + fg.length;
+			int pos = fgStart;
+			while (pos < fgEnd && bgIdx < backgrounds.size()) {
+				StyleRange bg = backgrounds.get(bgIdx);
+				int bgStart = bg.start;
+				int bgEnd = bg.start + bg.length;
+				if (bgEnd <= pos) {
+					bgIdx++;
+					continue;
+				}
+				if (bgStart >= fgEnd) {
+					break;
+				}
+				if (bgStart > pos) {
+					result.add(createRange(fg, pos, bgStart - pos, null));
+					pos = bgStart;
+				}
+				int overlapEnd = Math.min(bgEnd, fgEnd);
+				result.add(createRange(fg, pos, overlapEnd - pos, bg.background));
+				pos = overlapEnd;
+				if (bgEnd <= fgEnd) {
+					bgIdx++;
+				}
+			}
+			if (pos < fgEnd) {
+				result.add(createRange(fg, pos, fgEnd - pos, null));
+			}
+		}
+		return result;
+	}
+
+	private static StyleRange createRange(StyleRange base, int start, int length, Color background) {
+		StyleRange r = (StyleRange) base.clone();
+		r.start = start;
+		r.length = length;
+		if (background != null) {
+			r.background = background;
+		}
+		return r;
+	}
+}

team/tests/org.eclipse.team.tests.core/src/org/eclipse/team/tests/core/AllTeamUITests.java

@@ -16,6 +16,7 @@
 import org.eclipse.team.tests.core.mapping.AllTeamMappingTests;
 import org.eclipse.team.tests.ui.SaveableCompareEditorInputTest;
 import org.eclipse.team.tests.ui.UnifiedDiffManagerTest;
+import org.eclipse.team.tests.ui.UnifiedDiffTextTest;
 import org.eclipse.team.tests.ui.synchronize.AllTeamSynchronizeTests;
 import org.junit.platform.suite.api.SelectClasses;
 import org.junit.platform.suite.api.Suite;
@@ -26,6 +27,7 @@
 		AllTeamSynchronizeTests.class, //
 		SaveableCompareEditorInputTest.class, //
 		UnifiedDiffManagerTest.class, //
+		UnifiedDiffTextTest.class, //
 })
 public class AllTeamUITests {
 }