diff: do not hide breadcrumbs in folded ranges if method declaration is collapsed

Ex: if method has long JavaDoc and has modifications in JavaDoc and body, making method name invisible.

platform/diff-impl/src/com/intellij/diff/tools/fragmented/UnifiedDiffViewer.java

@@ -1317,7 +1317,7 @@ public class UnifiedDiffViewer extends ListenerDiffViewerBase {
 
       @Nullable
       @Override
-      protected String getDescription(int lineNumber, int index) {
+      protected FoldedRangeDescription getDescription(int lineNumber, int index) {
         if (myProject == null) return null;
         int masterLine = myLineConvertor.convert(lineNumber);
         if (masterLine == -1) return null;

platform/diff-impl/src/com/intellij/diff/tools/util/FoldingModelSupport.java

@@ -32,6 +32,7 @@ import com.intellij.psi.PsiFile;
 import com.intellij.ui.components.breadcrumbs.Crumb;
 import com.intellij.util.Function;
 import com.intellij.util.containers.ContainerUtil;
+import com.intellij.xml.breadcrumbs.NavigatableCrumb;
 import gnu.trove.TIntFunction;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
@@ -157,7 +158,7 @@ public class FoldingModelSupport {
 
     @Nullable
     @Override
-    protected String getDescription(int lineNumber, int index) {
+    protected FoldedRangeDescription getDescription(int lineNumber, int index) {
       if (myProject == null) return null;
       return getLineSeparatorDescription(myProject, myEditors[index].getDocument(), lineNumber);
     }
@@ -240,21 +241,27 @@ public class FoldingModelSupport {
 
       String[] descriptions = new String[myCount];
       for (int i = 0; i < myCount; i++) {
-        String startDescription = getDescription(starts[i], i);
-        String endDescription = getDescription(ends[i], i);
-        if (Comparing.equal(startDescription, endDescription)) continue;
-        descriptions[i] = endDescription;
+        FoldedRangeDescription startDescription = getDescription(starts[i], i);
+        FoldedRangeDescription endDescription = getDescription(ends[i], i);
+        if (endDescription == null) continue;
+        if (Comparing.equal(startDescription, endDescription) &&
+            !(endDescription.anchorLine != -1 && starts[i] <= endDescription.anchorLine)) {
+          continue;
+        }
+        descriptions[i] = endDescription.description;
       }
 
       return new Data.Block(regions, descriptions);
     }
 
     @Nullable
-    protected abstract String getDescription(int lineNumber, int index);
+    protected abstract FoldedRangeDescription getDescription(int lineNumber, int index);
   }
 
   @Nullable
-  protected static String getLineSeparatorDescription(@NotNull Project project, @NotNull Document document, int lineNumber) {
+  protected static FoldedRangeDescription getLineSeparatorDescription(@NotNull Project project,
+                                                                      @NotNull Document document,
+                                                                      int lineNumber) {
     return ReadAction.compute(() -> {
       ProgressManager.checkCanceled();
       PsiFile psiFile = PsiDocumentManager.getInstance(project).getPsiFile(document);
@@ -265,13 +272,43 @@ public class FoldingModelSupport {
       int offset = document.getLineStartOffset(lineNumber);
 
       FileBreadcrumbsCollector collector = FileBreadcrumbsCollector.findBreadcrumbsCollector(project, virtualFile);
-      Iterable<? extends Crumb> crumbs = collector.computeCrumbs(virtualFile, document, offset, null);
-      if (!crumbs.iterator().hasNext()) return null;
+      List<Crumb> crumbs = ContainerUtil.newArrayList(collector.computeCrumbs(virtualFile, document, offset, null));
+      if (crumbs.isEmpty()) return null;
 
-      return StringUtil.join(crumbs, it -> it.getText(), " > ");
+      String description = StringUtil.join(crumbs, it -> it.getText(), " > ");
+
+      Crumb lastCrumb = crumbs.get(crumbs.size() - 1);
+      int anchorOffset = lastCrumb instanceof NavigatableCrumb ? ((NavigatableCrumb)lastCrumb).getAnchorOffset() : -1;
+      int anchorLine = anchorOffset != -1 ? document.getLineNumber(anchorOffset) : -1;
+
+      return new FoldedRangeDescription(description, anchorLine);
     });
   }
 
+  protected static class FoldedRangeDescription {
+    @NotNull private final String description;
+    private final int anchorLine;
+
+    private FoldedRangeDescription(@NotNull String description, int anchorLine) {
+      this.description = description;
+      this.anchorLine = anchorLine;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+      FoldedRangeDescription that = (FoldedRangeDescription)o;
+      return Objects.equals(description, that.description) &&
+             Objects.equals(anchorLine, that.anchorLine);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(description, anchorLine);
+    }
+  }
+
   private class FoldingInstaller {
     @NotNull private final ExpandSuggester myExpandSuggester;
 

platform/platform-api/src/com/intellij/xml/breadcrumbs/NavigatableCrumb.java

@@ -1,4 +1,4 @@
-// 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.
+// 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.xml.breadcrumbs;
 
 import com.intellij.openapi.editor.Editor;
@@ -16,5 +16,7 @@ public interface NavigatableCrumb extends Crumb {
   @Nullable
   TextRange getHighlightRange();
 
+  default int getAnchorOffset() { return -1; }
+
   void navigate(@NotNull Editor editor, boolean withSelection);
 }

xml/impl/src/com/intellij/xml/breadcrumbs/PsiCrumb.java

@@ -37,6 +37,11 @@ final class PsiCrumb extends Crumb.Impl implements NavigatableCrumb {
     return tooltip;
   }
 
+  @Override
+  public int getAnchorOffset() {
+    PsiElement element = anchor.retrieve();
+    return element != null ? element.getTextOffset() : -1;
+  }
 
   @Override
   public TextRange getHighlightRange() {
@@ -46,10 +51,10 @@ final class PsiCrumb extends Crumb.Impl implements NavigatableCrumb {
 
   @Override
   public void navigate(@NotNull Editor editor, boolean withSelection) {
-    PsiElement element = anchor.retrieve();
-    if (element == null) return;
-
-    moveEditorCaretTo(editor, element.getTextOffset());
+    int offset = getAnchorOffset();
+    if (offset != -1) {
+      moveEditorCaretTo(editor, offset);
+    }
 
     if (withSelection) {
       final TextRange range = getHighlightRange();