lst: optimization - do not collect lines for unchanged prefix/suffix of the document

GitOrigin-RevId: 73f2a2f2512cb76966101040965731e1de799777

platform/diff-impl/src/com/intellij/diff/comparison/iterables/DiffIterableUtil.java

@@ -120,6 +120,13 @@ public class DiffIterableUtil {
     return new SubiterableDiffIterable(iterable, start1, end1, start2, end2);
   }
 
+  @NotNull
+  public static DiffIterable expandedIterable(@NotNull DiffIterable iterable, int offset1, int offset2, int length1, int length2) {
+    assert offset1 + iterable.getLength1() <= length1 &&
+           offset2 + iterable.getLength2() <= length2;
+    return new ExpandedDiffIterable(iterable, offset1, offset2, length1, length2);
+  }
+
   //
   // Misc
   //

platform/diff-impl/src/com/intellij/diff/comparison/iterables/ExpandedDiffIterable.java

@@ -0,0 +1,72 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.diff.comparison.iterables;
+
+import com.intellij.diff.util.Range;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Iterator;
+
+class ExpandedDiffIterable extends ChangeDiffIterableBase {
+  @NotNull private final DiffIterable myIterable;
+  private final int myOffset1;
+  private final int myOffset2;
+
+  ExpandedDiffIterable(@NotNull DiffIterable iterable, int offset1, int offset2, int length1, int length2) {
+    super(length1, length2);
+    myIterable = iterable;
+    myOffset1 = offset1;
+    myOffset2 = offset2;
+  }
+
+  @NotNull
+  @Override
+  protected ChangeIterable createChangeIterable() {
+    return new ShiftedChangeIterable(myIterable, myOffset1, myOffset2);
+  }
+
+  private static class ShiftedChangeIterable implements ChangeIterable {
+    private final Iterator<Range> myIterator;
+    private final int myOffset1;
+    private final int myOffset2;
+
+    private Range myLast;
+
+    ShiftedChangeIterable(@NotNull DiffIterable iterable, int offset1, int offset2) {
+      myIterator = iterable.changes();
+      myOffset1 = offset1;
+      myOffset2 = offset2;
+
+      next();
+    }
+
+    @Override
+    public boolean valid() {
+      return myLast != null;
+    }
+
+    @Override
+    public void next() {
+      myLast = myIterator.hasNext() ? myIterator.next() : null;
+    }
+
+    @Override
+    public int getStart1() {
+      return myLast.start1 + myOffset1;
+    }
+
+    @Override
+    public int getStart2() {
+      return myLast.start2 + myOffset2;
+    }
+
+    @Override
+    public int getEnd1() {
+      return myLast.end1 + myOffset1;
+    }
+
+    @Override
+    public int getEnd2() {
+      return myLast.end2 + myOffset2;
+    }
+  }
+}

platform/diff-impl/src/com/intellij/openapi/vcs/ex/RangesBuilder.kt

@@ -29,6 +29,7 @@ import com.intellij.diff.util.Side
 import com.intellij.openapi.editor.Document
 import com.intellij.openapi.progress.DumbProgressIndicator
 import java.util.*
+import kotlin.math.max
 
 fun createRanges(current: List<String>,
                  vcs: List<String>,
@@ -63,9 +64,16 @@ fun compareLines(text1: CharSequence,
                  text2: CharSequence,
                  lineOffsets1: LineOffsets,
                  lineOffsets2: LineOffsets): FairDiffIterable {
-  val lines1 = DiffUtil.getLines(text1, lineOffsets1)
-  val lines2 = DiffUtil.getLines(text2, lineOffsets2)
-  return compareLines(lines1, lines2)
+  val range = expand(text1, text2, 0, 0, text1.length, text2.length)
+  if (range.isEmpty) return fair(DiffIterableUtil.create(emptyList(), lineOffsets1.lineCount, lineOffsets2.lineCount));
+
+  val start = lineOffsets1.getLineNumber(range.start1)
+  val end1 = lineOffsets1.getLineNumber(range.end1)
+  val tail = max(lineOffsets1.lineCount - end1 - 1, 0)
+  val lineRange = Range(start, lineOffsets1.lineCount - tail, start, lineOffsets2.lineCount - tail)
+
+  val iterable = compareLines(lineRange, text1, text2, lineOffsets1, lineOffsets2)
+  return fair(DiffIterableUtil.expandedIterable(iterable, start, start, lineOffsets1.lineCount, lineOffsets2.lineCount))
 }
 
 fun compareLines(lineRange: Range,

platform/vcs-tests/testSrc/com/intellij/openapi/vcs/BaseLineStatusTrackerManagerTest.kt

@@ -1,6 +1,7 @@
 // Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.openapi.vcs
 
+import com.intellij.diff.comparison.iterables.DiffIterableUtil
 import com.intellij.openapi.application.ApplicationManager
 import com.intellij.openapi.application.runWriteAction
 import com.intellij.openapi.command.CommandProcessor
@@ -10,6 +11,7 @@ import com.intellij.openapi.command.undo.DocumentReferenceProvider
 import com.intellij.openapi.command.undo.UndoManager
 import com.intellij.openapi.editor.Document
 import com.intellij.openapi.fileEditor.FileEditor
+import com.intellij.openapi.util.registry.Registry
 import com.intellij.openapi.vcs.BaseLineStatusTrackerTestCase.Companion.parseInput
 import com.intellij.openapi.vcs.changes.shelf.ShelveChangesManager
 import com.intellij.openapi.vcs.ex.*
@@ -28,6 +30,7 @@ abstract class BaseLineStatusTrackerManagerTest : BaseChangeListsTest() {
   override fun setUp() {
     super.setUp()
 
+    DiffIterableUtil.setVerifyEnabled(true)
     lstm = LineStatusTrackerManager.getInstanceImpl(getProject())
     undoManager = UndoManager.getInstance(getProject()) as UndoManagerImpl
     shelveManager = ShelveChangesManager.getInstance(getProject())
@@ -39,6 +42,7 @@ abstract class BaseLineStatusTrackerManagerTest : BaseChangeListsTest() {
       .append(ThrowableRunnable { UIUtil.dispatchAllInvocationEvents() })
       .append(ThrowableRunnable { lstm.resetExcludedFromCommitMarkers() })
       .append(ThrowableRunnable { lstm.releaseAllTrackers() })
+      .append(ThrowableRunnable { DiffIterableUtil.setVerifyEnabled(Registry.`is`("diff.verify.iterable")) })
       .append(ThrowableRunnable { super.tearDown() })
       .run()
   }

platform/vcs-tests/testSrc/com/intellij/openapi/vcs/LineStatusTrackerModifyDocumentTest.kt

@@ -18,6 +18,52 @@ package com.intellij.openapi.vcs
 import com.intellij.openapi.vcs.ex.Range
 
 class LineStatusTrackerModifyDocumentTest : BaseLineStatusTrackerTestCase() {
+  fun testInitialEmpty() {
+    test("", "") {
+      assertRanges()
+      compareRanges()
+    }
+  }
+
+  fun testInitialEquals() {
+    test("1234_2345_3456",
+         "1234_2345_3456") {
+      assertRanges()
+      compareRanges()
+    }
+  }
+
+  fun testInitialInsertion() {
+    test("1234_2345_3456",
+         "1234_3456") {
+      assertRanges(Range(1, 2, 1, 1))
+      compareRanges()
+    }
+  }
+
+  fun testInitialDeletion() {
+    test("1234_3456", "1234_2345_3456") {
+      assertRanges(Range(1, 1, 1, 2))
+      compareRanges()
+    }
+  }
+
+  fun testInitialModification1() {
+    test("1234_x_3456", "1234_2345_3456") {
+      assertRanges(Range(1, 2, 1, 2))
+      compareRanges()
+    }
+  }
+
+  fun testInitialModification2() {
+    test("1_3_4_5_6_7", "1_2_3_5_6_12") {
+      assertRanges(Range(1, 1, 1, 2),
+                   Range(2, 3, 3, 3),
+                   Range(5, 6, 5, 6))
+      compareRanges()
+    }
+  }
+
   fun testSimpleInsert() {
     test("1234_2345_3456") {
       "12".insertAfter("a")