java-diff-utils · wumpz · Feb 5, 2025 · Jul 30, 2024 · Feb 5, 2025 · wumpz
diff --git a/java-diff-utils/src/main/java/com/github/difflib/text/DiffRowGenerator.java b/java-diff-utils/src/main/java/com/github/difflib/text/DiffRowGenerator.java
@@ -24,6 +24,8 @@
 import com.github.difflib.patch.InsertDelta;
 import com.github.difflib.patch.Patch;
 import com.github.difflib.text.DiffRow.Tag;
+import com.github.difflib.text.deltamerge.DeltaMergeUtils;
+import com.github.difflib.text.deltamerge.InlineDeltaMergeInfo;
 import java.util.*;
 import java.util.function.BiFunction;
 import java.util.function.BiPredicate;
@@ -75,6 +77,14 @@ public final class DiffRowGenerator {
     public static final Function<String, List<String>> SPLITTER_BY_WORD = line -> splitStringPreserveDelimiter(line, SPLIT_BY_WORD_PATTERN);
     public static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");
 
+    public static final Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> DEFAULT_INLINE_DELTA_MERGER = InlineDeltaMergeInfo::getDeltas;
+
+    /**
+     * Merge diffs which are separated by equalities consisting of whitespace only.
+     */
+    public static final Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> WHITESPACE_EQUALITIES_MERGER = deltaMergeInfo -> DeltaMergeUtils
+            .mergeInlineDeltas(deltaMergeInfo, (equalities -> equalities.stream().allMatch(String::isBlank)));
+
     public static Builder create() {
         return new Builder();
     }
@@ -170,6 +180,7 @@ static void wrapInTag(List<String> sequence, int startPosition,
     private final boolean reportLinesUnchanged;
     private final Function<String, String> lineNormalizer;
     private final Function<String, String> processDiffs;
+    private final Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> inlineDeltaMerger;
 
     private final boolean showInlineDiffs;
     private final boolean replaceOriginalLinefeedInChangesWithSpaces;
@@ -194,11 +205,13 @@ private DiffRowGenerator(Builder builder) {
         reportLinesUnchanged = builder.reportLinesUnchanged;
         lineNormalizer = builder.lineNormalizer;
         processDiffs = builder.processDiffs;
+        inlineDeltaMerger = builder.inlineDeltaMerger;
 
         replaceOriginalLinefeedInChangesWithSpaces = builder.replaceOriginalLinefeedInChangesWithSpaces;
 
         Objects.requireNonNull(inlineDiffSplitter);
         Objects.requireNonNull(lineNormalizer);
+        Objects.requireNonNull(inlineDeltaMerger);
     }
 
     /**
@@ -370,7 +383,10 @@ private List<DiffRow> generateInlineDiffs(AbstractDelta<String> delta) {
         origList = inlineDiffSplitter.apply(joinedOrig);
         revList = inlineDiffSplitter.apply(joinedRev);
 
-        List<AbstractDelta<String>> inlineDeltas = DiffUtils.diff(origList, revList, equalizer).getDeltas();
+        List<AbstractDelta<String>> originalInlineDeltas = DiffUtils.diff(origList, revList, equalizer)
+                .getDeltas();
+        List<AbstractDelta<String>> inlineDeltas = inlineDeltaMerger
+                .apply(new InlineDeltaMergeInfo(originalInlineDeltas, origList, revList));
 
         Collections.reverse(inlineDeltas);
         for (AbstractDelta<String> inlineDelta : inlineDeltas) {
@@ -465,6 +481,7 @@ public static class Builder {
         private Function<String, String> processDiffs = null;
         private BiPredicate<String, String> equalizer = null;
         private boolean replaceOriginalLinefeedInChangesWithSpaces = false;
+        private Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> inlineDeltaMerger = DEFAULT_INLINE_DELTA_MERGER;
 
         private Builder() {
         }
@@ -673,5 +690,17 @@ public Builder replaceOriginalLinefeedInChangesWithSpaces(boolean replace) {
             this.replaceOriginalLinefeedInChangesWithSpaces = replace;
             return this;
         }
+
+        /**
+         * Provide an inline delta merger for use case specific delta optimizations.
+         *
+         * @param inlineDeltaMerger
+         * @return
+         */
+        public Builder inlineDeltaMerger(
+                Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> inlineDeltaMerger) {
+            this.inlineDeltaMerger = inlineDeltaMerger;
+            return this;
+        }
     }
 }
diff --git a/java-diff-utils/src/main/java/com/github/difflib/text/deltamerge/DeltaMergeUtils.java b/java-diff-utils/src/main/java/com/github/difflib/text/deltamerge/DeltaMergeUtils.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2009-2024 java-diff-utils.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.github.difflib.text.deltamerge;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+import com.github.difflib.patch.AbstractDelta;
+import com.github.difflib.patch.ChangeDelta;
+import com.github.difflib.patch.Chunk;
+
+/**
+ * Provides utility features for merge inline deltas
+ *
+ * @author <a href="[email protected]">Christian Meier</a>
+ */
+final public class DeltaMergeUtils {
+
+    public static List<AbstractDelta<String>> mergeInlineDeltas(InlineDeltaMergeInfo deltaMergeInfo,
+            Predicate<List<String>> replaceEquality) {
+        final List<AbstractDelta<String>> originalDeltas = deltaMergeInfo.getDeltas();
+        if (originalDeltas.size() < 2) {
+            return originalDeltas;
+        }
+
+        final List<AbstractDelta<String>> newDeltas = new ArrayList<>();
+        newDeltas.add(originalDeltas.get(0));
+        for (int i = 1; i < originalDeltas.size(); i++) {
+            final AbstractDelta<String> previousDelta = newDeltas.getLast();
+            final AbstractDelta<String> currentDelta = originalDeltas.get(i);
+
+            final List<String> equalities = deltaMergeInfo.getOrigList().subList(
+                    previousDelta.getSource().getPosition() + previousDelta.getSource().size(),
+                    currentDelta.getSource().getPosition());
+
+            if (replaceEquality.test(equalities)) {
+                // Merge the previous delta, the equality and the current delta into one
+                // ChangeDelta and replace the previous delta by this new ChangeDelta.
+                final List<String> allSourceLines = new ArrayList<>();
+                allSourceLines.addAll(previousDelta.getSource().getLines());
+                allSourceLines.addAll(equalities);
+                allSourceLines.addAll(currentDelta.getSource().getLines());
+
+                final List<String> allTargetLines = new ArrayList<>();
+                allTargetLines.addAll(previousDelta.getTarget().getLines());
+                allTargetLines.addAll(equalities);
+                allTargetLines.addAll(currentDelta.getTarget().getLines());
+
+                final ChangeDelta<String> replacement = new ChangeDelta<>(
+                        new Chunk<>(previousDelta.getSource().getPosition(), allSourceLines),
+                        new Chunk<>(previousDelta.getTarget().getPosition(), allTargetLines));
+
+                newDeltas.removeLast();
+                newDeltas.add(replacement);
+            } else {
+                newDeltas.add(currentDelta);
+            }
+        }
+
+        return newDeltas;
+    }
+
+    private DeltaMergeUtils() {
+    }
+}
diff --git a/java-diff-utils/src/main/java/com/github/difflib/text/deltamerge/InlineDeltaMergeInfo.java b/java-diff-utils/src/main/java/com/github/difflib/text/deltamerge/InlineDeltaMergeInfo.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2009-2024 java-diff-utils.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.github.difflib.text.deltamerge;
+
+import java.util.List;
+
+import com.github.difflib.patch.AbstractDelta;
+
+/**
+ * Holds the information required to merge deltas originating from an inline
+ * diff
+ *
+ * @author <a href="[email protected]">Christian Meier</a>
+ */
+public final class InlineDeltaMergeInfo {
+
+    private final List<AbstractDelta<String>> deltas;
+    private final List<String> origList;
+    private final List<String> revList;
+
+    public InlineDeltaMergeInfo(List<AbstractDelta<String>> deltas, List<String> origList, List<String> revList) {
+        this.deltas = deltas;
+        this.origList = origList;
+        this.revList = revList;
+    }
+
+    public List<AbstractDelta<String>> getDeltas() {
+        return deltas;
+    }
+
+    public List<String> getOrigList() {
+        return origList;
+    }
+
+    public List<String> getRevList() {
+        return revList;
+    }
+}
diff --git a/java-diff-utils/src/test/java/com/github/difflib/text/DiffRowGeneratorTest.java b/java-diff-utils/src/test/java/com/github/difflib/text/DiffRowGeneratorTest.java
@@ -12,6 +12,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Function;
 import java.util.regex.Pattern;
 import static java.util.stream.Collectors.joining;
 import static java.util.stream.Collectors.toList;
@@ -20,6 +21,10 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import org.junit.jupiter.api.Test;
 
+import com.github.difflib.patch.AbstractDelta;
+import com.github.difflib.text.deltamerge.DeltaMergeUtils;
+import com.github.difflib.text.deltamerge.InlineDeltaMergeInfo;
+
 public class DiffRowGeneratorTest {
 
     @Test
@@ -791,6 +796,47 @@ public void testIssue129SkipWhitespaceChanges() throws IOException {
                 .forEach(System.out::println);
     }
 
+    @Test
+    public void testGeneratorWithWhitespaceDeltaMerge() {
+        final DiffRowGenerator generator = DiffRowGenerator.create().showInlineDiffs(true).mergeOriginalRevised(true)
+                .inlineDiffByWord(true).oldTag(f -> "~").newTag(f -> "**") //
+                .lineNormalizer(StringUtils::htmlEntites) // do not replace tabs
+                .inlineDeltaMerger(DiffRowGenerator.WHITESPACE_EQUALITIES_MERGER).build();
+
+        assertInlineDiffResult(generator, "No diff", "No diff", "No diff");
+        assertInlineDiffResult(generator, " x whitespace before diff", " y whitespace before diff",
+                " ~x~**y** whitespace before diff");
+        assertInlineDiffResult(generator, "Whitespace after diff x ", "Whitespace after diff y ",
+                "Whitespace after diff ~x~**y** ");
+        assertInlineDiffResult(generator, "Diff x x between", "Diff y y between", "Diff ~x x~**y y** between");
+        assertInlineDiffResult(generator, "Hello \t world", "Hi \t universe", "~Hello \t world~**Hi \t universe**");
+        assertInlineDiffResult(generator, "The quick brown fox jumps over the lazy dog", "A lazy dog jumps over a fox",
+                "~The quick brown fox ~**A lazy dog **jumps over ~the lazy dog~**a fox**");
+    }
+
+    @Test
+    public void testGeneratorWithMergingDeltasForShortEqualities() {
+        final Function<InlineDeltaMergeInfo, List<AbstractDelta<String>>> shortEqualitiesMerger = deltaMergeInfo -> DeltaMergeUtils
+                .mergeInlineDeltas(deltaMergeInfo,
+                        (equalities -> equalities.stream().mapToInt(String::length).sum() < 6));
+
+        final DiffRowGenerator generator = DiffRowGenerator.create().showInlineDiffs(true).mergeOriginalRevised(true)
+                .inlineDiffByWord(true).oldTag(f -> "~").newTag(f -> "**").inlineDeltaMerger(shortEqualitiesMerger)
+                .build();
+
+        assertInlineDiffResult(generator, "No diff", "No diff", "No diff");
+        assertInlineDiffResult(generator, "aaa bbb ccc", "xxx bbb zzz", "~aaa bbb ccc~**xxx bbb zzz**");
+        assertInlineDiffResult(generator, "aaa bbbb ccc", "xxx bbbb zzz", "~aaa~**xxx** bbbb ~ccc~**zzz**");
+    }
+
+    private void assertInlineDiffResult(DiffRowGenerator generator, String original, String revised, String expected) {
+        final List<DiffRow> rows = generator.generateDiffRows(Arrays.asList(original), Arrays.asList(revised));
+        print(rows);
+
+        assertEquals(1, rows.size());
+        assertEquals(expected, rows.get(0).getOldLine().toString());
+    }
+
     @Test
     public void testIssue188HangOnExamples() throws IOException, URISyntaxException {        
         try (FileSystem zipFs = FileSystems.newFileSystem(Paths.get("target/test-classes/com/github/difflib/text/test.zip"), null);) {