RUBY-12492 Supported aliases in file structure

Also org.jetbrains.yaml.structureView package was refactored

plugins/yaml/resources/messages/YAMLBundle.properties

@@ -40,6 +40,9 @@ YamlScalarType.error.scalar.value=Scalar value expected
 YamlIntegerType.error.integer.value=Integer value expected
 YamlNumberType.error.numeric.value=Numeric value expected
 
+YAMLStructureViewDocument.element.name=YAML document
+YAMLStructureViewSequenceItem.element.name=Sequence Item
+
 YAMLParser.invalid.header.symbols=Invalid block scalar header
 YAMLParser.multiple.anchors=Multiple anchors are not permitted
 YAMLParser.multiple.tags=Multiple tags are not permitted
@@ -47,6 +50,9 @@ YAMLParser.multiple.tags=Multiple tags are not permitted
 YAMLAnchorRenameProcessor.lost.alias=Alias will refer to another anchor
 YAMLAnchorRenameProcessor.reuse=Anchor already has the same name
 
+YAMLAliasResolveNodeProvider.action.name=Show aliased sub-trees
+YAMLAliasResolveNodeProvider.action.description=Resolve aliases and show referenced values in the structure
+
 inspections.group.name=YAML
 inspections.unresolved.alias.name=Unresolved alias
 inspections.unresolved.alias.message=Can''t resolve alias {0}

plugins/yaml/src/org/jetbrains/yaml/structureView/DuplicatedPsiTreeElementBase.java

@@ -0,0 +1,175 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.ide.structureView.impl.common.PsiTreeElementBase;
+import com.intellij.ide.util.treeView.AbstractTreeUi;
+import com.intellij.ide.util.treeView.NodeDescriptorProvidingKey;
+import com.intellij.ide.util.treeView.TreeAnchorizer;
+import com.intellij.navigation.ItemPresentation;
+import com.intellij.pom.Navigatable;
+import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collection;
+import java.util.Objects;
+
+/**
+ * File structure popup work with unique values (see {@link StructureViewTreeElement#getValue()}).
+ * If it is needed to show the same PSI element several times then each occurrence of such psi should be wrapped to some unique object.
+ * This class perform this task.
+ * <p/>
+ * This class could be moved to some common platform package if it will be needed for somebody else.
+ * The implementation of this class is based on {@link PsiTreeElementBase} implementation (copy-pasted and modified).
+ */
+abstract class DuplicatedPsiTreeElementBase<T extends PsiElement & Navigatable> implements StructureViewTreeElement,
+                                                                                           ItemPresentation,
+                                                                                           NodeDescriptorProvidingKey {
+  @NotNull
+  private final StoredData<T> myValue;
+
+  /** @param details is used to distinguish different occurrences of the same PSI element */
+  protected DuplicatedPsiTreeElementBase(@NotNull T psiElement, @NotNull String details) {
+    myValue = new StoredData<>(psiElement, details);
+  }
+
+  /** @return stored psi element */
+  @NotNull
+  public final T getElement() {
+    return getValue().getElement();
+  }
+
+  /** @return additional information which is used to distinguish different occurrences of the same PSI element */
+  @NotNull
+  public final String getDetails() {
+    return getValue().getDetails();
+  }
+
+  @NotNull
+  public abstract Collection<StructureViewTreeElement> getChildrenBase();
+
+  @NotNull
+  @Override
+  public ItemPresentation getPresentation() {
+    return this;
+  }
+
+  @NotNull
+  @Override
+  public Object getKey() {
+    return String.valueOf(getElement());
+  }
+
+  @Contract(pure = true)
+  @NotNull
+  @Override
+  public final StoredData<T> getValue() {
+    return myValue;
+  }
+
+  public String toString() {
+    return getElement().toString();
+  }
+
+  @NotNull
+  @Override
+  public final StructureViewTreeElement[] getChildren() {
+    return AbstractTreeUi.calculateYieldingToWriteAction(this::doGetChildren);
+  }
+
+  @NotNull
+  private StructureViewTreeElement[] doGetChildren() {
+    return PsiTreeElementBase.mergeWithExtensions(getElement(), getChildrenBase());
+  }
+
+  @Override
+  public void navigate(boolean requestFocus) {
+    getElement().navigate(requestFocus);
+  }
+
+  @Override
+  public boolean canNavigate() {
+    return getElement().canNavigate();
+  }
+
+  @Override
+  public boolean canNavigateToSource() {
+    return canNavigate();
+  }
+
+  @Contract(value = "null -> false", pure = true)
+  public boolean equals(@Nullable Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+
+    final DuplicatedPsiTreeElementBase that = (DuplicatedPsiTreeElementBase)o;
+
+    return getValue().equals(that.getValue());
+  }
+
+  public int hashCode() {
+    return getValue().hashCode();
+  }
+
+  public boolean isValid() {
+    return true;
+  }
+
+  /** This class is a wrapper over PSI element with additional information */
+  private static class StoredData<T extends Navigatable> implements Navigatable {
+    @NotNull
+    private final Object myAnchor;
+    @NotNull
+    private final String myDetails;
+
+    public StoredData(@NotNull T element, @NotNull String details) {
+      myAnchor = TreeAnchorizer.getService().createAnchor(element);
+      myDetails = details;
+    }
+
+    @NotNull
+    public T getElement() {
+      @SuppressWarnings("unchecked")
+      T element = (T)TreeAnchorizer.getService().retrieveElement(myAnchor);
+      assert element != null;
+      return element;
+    }
+
+    @NotNull
+    public String getDetails() {
+      return myDetails;
+    }
+
+    @Override
+    public void navigate(boolean requestFocus) {
+      getElement().navigate(requestFocus);
+    }
+
+    @Override
+    public boolean canNavigate() {
+      return getElement().canNavigate();
+    }
+
+    @Override
+    public boolean canNavigateToSource() {
+      return getElement().canNavigateToSource();
+    }
+
+    @Contract(value = "null -> false", pure = true)
+    @Override
+    public boolean equals(@Nullable Object o) {
+      if (this == o) return true;
+      if (o == null || getClass() != o.getClass()) return false;
+      StoredData<?> data = (StoredData<?>)o;
+      return Objects.equals(getElement(), data.getElement()) &&
+             Objects.equals(getDetails(), data.getDetails());
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(getElement(), getDetails());
+    }
+  }
+}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLAliasResolveNodeProvider.java

@@ -0,0 +1,103 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.ide.util.ActionShortcutProvider;
+import com.intellij.ide.util.FileStructureNodeProvider;
+import com.intellij.ide.util.treeView.smartTree.ActionPresentation;
+import com.intellij.ide.util.treeView.smartTree.ActionPresentationData;
+import com.intellij.ide.util.treeView.smartTree.TreeElement;
+import com.intellij.openapi.actionSystem.Shortcut;
+import com.intellij.openapi.util.Ref;
+import com.intellij.psi.PsiElement;
+import com.intellij.util.IncorrectOperationException;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NonNls;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.yaml.YAMLBundle;
+import org.jetbrains.yaml.psi.*;
+import org.jetbrains.yaml.resolve.YAMLAliasReference;
+
+import java.util.Collection;
+import java.util.Collections;
+
+public class YAMLAliasResolveNodeProvider implements FileStructureNodeProvider<StructureViewTreeElement>, ActionShortcutProvider {
+  @NonNls public static final String ID = "YAML_SHOW_RESOLVED_ALIAS_VALUES";
+
+  @NotNull
+  @Override
+  public String getCheckBoxText() {
+    return YAMLBundle.message("YAMLAliasResolveNodeProvider.action.name");
+  }
+
+  @NotNull
+  @Override
+  public Shortcut[] getShortcut() {
+    throw new IncorrectOperationException("see getActionIdForShortcut()");
+  }
+
+  @NotNull
+  @Override
+  public String getActionIdForShortcut() {
+    return "FileStructurePopup";
+  }
+
+  @NotNull
+  @Override
+  public Collection<StructureViewTreeElement> provideNodes(@NotNull TreeElement node) {
+    if (!(node instanceof DuplicatedPsiTreeElementBase)) {
+      return Collections.emptyList();
+    }
+    DuplicatedPsiTreeElementBase yamlNode = (DuplicatedPsiTreeElementBase)node;
+    PsiElement psiElem = yamlNode.getElement();
+    YAMLPsiElement yamlElem = psiElem instanceof YAMLPsiElement ? (YAMLPsiElement)psiElem : null;
+    YAMLValue value = getContainedValue(yamlElem);
+    if (!(value instanceof YAMLAlias)) {
+      return Collections.emptyList();
+    }
+    return YAMLStructureViewFactory.createChildrenViewTreeElements(resolveAlias((YAMLAlias)value), yamlNode.getDetails());
+  }
+
+  @NotNull
+  @Override
+  public ActionPresentation getPresentation() {
+    return new ActionPresentationData(YAMLBundle.message("YAMLAliasResolveNodeProvider.action.name"),
+                                      YAMLBundle.message("YAMLAliasResolveNodeProvider.action.description"),
+                                      YAMLStructureViewFactory.ALIAS_ICON);
+  }
+
+  @NotNull
+  @Override
+  public String getName() {
+    return ID;
+  }
+
+  @Nullable
+  private static YAMLValue resolveAlias(@NotNull YAMLAlias alias) {
+    YAMLAliasReference ref = alias.getReference();
+    YAMLAnchor anchor = ref == null ? null : ref.resolve();
+    return anchor != null ? anchor.getMarkedValue() : null;
+  }
+
+  @Nullable
+  @Contract("null -> null")
+  private static YAMLValue getContainedValue(@Nullable YAMLPsiElement element) {
+    if (element == null) {
+      return null;
+    }
+    Ref<YAMLValue> result = Ref.create();
+    element.accept(new YamlPsiElementVisitor() {
+      @Override
+      public void visitKeyValue(@NotNull YAMLKeyValue keyValue) {
+        result.set(keyValue.getValue());
+      }
+
+      @Override
+      public void visitSequenceItem(@NotNull YAMLSequenceItem sequenceItem) {
+        result.set(sequenceItem.getValue());
+      }
+    });
+    return result.get();
+  }
+}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewBuilder.java

@@ -1,31 +0,0 @@
-package org.jetbrains.yaml.structureView;
-
-import com.intellij.ide.structureView.StructureViewModel;
-import com.intellij.ide.structureView.StructureViewModelBase;
-import com.intellij.ide.structureView.TreeBasedStructureViewBuilder;
-import com.intellij.ide.util.treeView.smartTree.Sorter;
-import com.intellij.openapi.editor.Editor;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-import org.jetbrains.yaml.psi.YAMLDocument;
-import org.jetbrains.yaml.psi.YAMLFile;
-import org.jetbrains.yaml.psi.YAMLKeyValue;
-
-/**
- * @author oleg
- */
-public class YAMLStructureViewBuilder extends TreeBasedStructureViewBuilder {
-  private final YAMLFile myPsiFile;
-
-  public YAMLStructureViewBuilder(@NotNull final YAMLFile psiFile) {
-    myPsiFile = psiFile;
-  }
-
-  @Override
-  @NotNull
-  public StructureViewModel createStructureViewModel(@Nullable Editor editor) {
-    return new StructureViewModelBase(myPsiFile, editor, new YAMLStructureViewElement(myPsiFile))
-      .withSorters(Sorter.ALPHA_SORTER)
-      .withSuitableClasses(YAMLFile.class, YAMLDocument.class, YAMLKeyValue.class);
-  }
-}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewDocument.java

@@ -0,0 +1,36 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.ide.structureView.impl.common.PsiTreeElementBase;
+import com.intellij.util.PlatformIcons;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.yaml.YAMLBundle;
+import org.jetbrains.yaml.psi.YAMLDocument;
+
+import javax.swing.*;
+import java.util.Collection;
+import java.util.Objects;
+
+class YAMLStructureViewDocument extends PsiTreeElementBase<YAMLDocument> {
+  YAMLStructureViewDocument(@NotNull YAMLDocument psiElement) {
+    super(psiElement);
+  }
+
+  @NotNull
+  @Override
+  public Collection<StructureViewTreeElement> getChildrenBase() {
+    YAMLDocument document = Objects.requireNonNull(getElement());
+    return YAMLStructureViewFactory.createChildrenViewTreeElements(document.getTopLevelValue(), "<doc>");
+  }
+
+  @NotNull
+  public String getPresentableText() {
+    return YAMLBundle.message("YAMLStructureViewDocument.element.name");
+  }
+
+  @NotNull
+  public Icon getIcon(boolean open) {
+    return PlatformIcons.XML_TAG_ICON;
+  }
+}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewElement.java

@@ -1,150 +0,0 @@
-package org.jetbrains.yaml.structureView;
-
-import com.intellij.ide.structureView.StructureViewTreeElement;
-import com.intellij.navigation.ItemPresentation;
-import com.intellij.util.PlatformIcons;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-import org.jetbrains.yaml.psi.*;
-
-import javax.swing.*;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-
-/**
- * @author oleg
- */
-public class YAMLStructureViewElement implements StructureViewTreeElement {
-  private final YAMLPsiElement myElement;
-
-  public YAMLStructureViewElement(final YAMLPsiElement element) {
-    myElement = element;
-  }
-
-  @NotNull
-  public StructureViewTreeElement[] getChildren() {
-    final Collection<? extends YAMLPsiElement> children;
-    if (myElement instanceof YAMLFile) {
-      children = ((YAMLFile)myElement).getDocuments();
-    }
-    else if (myElement instanceof YAMLDocument) {
-      children = getChildrenForValue(((YAMLDocument)myElement).getTopLevelValue());
-    }
-    else if (myElement instanceof YAMLSequenceItem) {
-      children = getChildrenForValue(((YAMLSequenceItem)myElement).getValue());
-    }
-    else if (myElement instanceof YAMLKeyValue) {
-      children = getChildrenForValue(((YAMLKeyValue)myElement).getValue());
-    }
-    else {
-      children = Collections.emptyList();
-    }
-    
-    final List<StructureViewTreeElement> structureElements = new ArrayList<>();
-    for (YAMLPsiElement child : children) {
-      structureElements.add(new YAMLStructureViewElement(child));
-    }
-    return structureElements.toArray(StructureViewTreeElement.EMPTY_ARRAY);
-  }
-  
-  @NotNull
-  private static Collection<? extends YAMLPsiElement> getChildrenForValue(@Nullable YAMLPsiElement element) {
-    if (element instanceof YAMLMapping) {
-      return ((YAMLMapping)element).getKeyValues();
-    }
-    if (element instanceof YAMLSequence) {
-      return ((YAMLSequence)element).getItems();
-    }
-    return Collections.emptyList();
-  }
-  
-
-
-  @NotNull
-  public ItemPresentation getPresentation() {
-    if (myElement instanceof YAMLKeyValue){
-      final YAMLKeyValue kv = (YAMLKeyValue)myElement;
-      return new ItemPresentation() {
-        public String getPresentableText() {
-          return kv.getKeyText();
-        }
-
-        public String getLocationString() {
-          if (kv.getValue() instanceof YAMLScalar) {
-            return kv.getValueText();
-          }
-          else {
-            return null;
-          }
-        }
-
-        public Icon getIcon(boolean open) {
-          final YAMLValue value = kv.getValue();
-          return value instanceof YAMLScalar ? kv.getIcon(0) : PlatformIcons.XML_TAG_ICON;
-        }
-      };
-    }
-    if (myElement instanceof YAMLDocument){
-      return new ItemPresentation() {
-        public String getPresentableText() {
-          return "YAML document";
-        }
-
-        public String getLocationString() {
-          return null;
-        }
-
-        public Icon getIcon(boolean open) {
-          return PlatformIcons.XML_TAG_ICON;
-        }
-      };
-    }
-    if (myElement instanceof YAMLSequenceItem) {
-      final YAMLSequenceItem item = ((YAMLSequenceItem)myElement);
-      return new ItemPresentation() {
-        @Nullable
-        @Override
-        public String getPresentableText() {
-          if (item.getValue() instanceof YAMLScalar) {
-            return ((YAMLScalar)item.getValue()).getTextValue();
-          }
-          else {
-            return "Sequence Item";
-          }
-        }
-
-        @Nullable
-        @Override
-        public String getLocationString() {
-          return null;
-        }
-
-        @Nullable
-        @Override
-        public Icon getIcon(boolean unused) {
-          return item.getValue() instanceof YAMLScalar ? PlatformIcons.PROPERTY_ICON : PlatformIcons.XML_TAG_ICON;
-        }
-      };
-    }
-    return myElement.getPresentation();
-  }
-
-  public YAMLPsiElement getValue() {
-    return myElement;
-  }
-
-  public void navigate(boolean requestFocus) {
-    myElement.navigate(requestFocus);
-  }
-
-  public boolean canNavigate() {
-    return myElement.canNavigate();
-  }
-
-  public boolean canNavigateToSource() {
-    return myElement.canNavigateToSource();
-  }
-}
-

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewFactory.java

@@ -1,16 +1,34 @@
 package org.jetbrains.yaml.structureView;
 
-import com.intellij.ide.structureView.StructureViewBuilder;
+import com.intellij.icons.AllIcons;
+import com.intellij.ide.structureView.*;
+import com.intellij.ide.util.treeView.smartTree.NodeProvider;
+import com.intellij.ide.util.treeView.smartTree.Sorter;
 import com.intellij.lang.PsiStructureViewFactory;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.util.Ref;
 import com.intellij.psi.PsiFile;
+import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.yaml.psi.YAMLFile;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.yaml.psi.*;
+
+import javax.swing.*;
+import java.util.Collection;
+import java.util.Collections;
 
 /**
  * @author oleg
  */
 public class YAMLStructureViewFactory implements PsiStructureViewFactory {
+  static final Icon ALIAS_ICON = AllIcons.Nodes.ExpandNode;
+
+  @Nullable
   public StructureViewBuilder getStructureViewBuilder(@NotNull final PsiFile psiFile) {
+    if (!(psiFile instanceof YAMLFile)) {
+      return null;
+    }
+
     for (YAMLCustomStructureViewFactory extension : YAMLCustomStructureViewFactory.EP_NAME.getExtensions()) {
       final StructureViewBuilder builder = extension.getStructureViewBuilder((YAMLFile)psiFile);
       if (builder != null) {
@@ -18,6 +36,44 @@ public class YAMLStructureViewFactory implements PsiStructureViewFactory {
       }
     }
 
-    return new YAMLStructureViewBuilder((YAMLFile) psiFile);
+    return new TreeBasedStructureViewBuilder() {
+      @Override
+      @NotNull
+      public StructureViewModel createStructureViewModel(@Nullable Editor editor) {
+        return new StructureViewModelBase(psiFile, editor, new YAMLStructureViewFile((YAMLFile)psiFile)){
+          @NotNull
+          @Override
+          public Collection<NodeProvider> getNodeProviders() {
+            return Collections.singleton(new YAMLAliasResolveNodeProvider());
+          }
+        }
+          .withSorters(Sorter.ALPHA_SORTER)
+          .withSuitableClasses(YAMLFile.class, YAMLDocument.class, YAMLKeyValue.class);
+      }
+    };
+  }
+
+  @NotNull
+  static String getAliasPresentableText(@NotNull YAMLAlias alias) {
+    return "*" + alias.getAliasName();
+  }
+
+  @NotNull
+  static Collection<StructureViewTreeElement> createChildrenViewTreeElements(@Nullable YAMLPsiElement element, String path) {
+    if (element == null) {
+      return Collections.emptyList();
+    }
+    Ref<Collection<StructureViewTreeElement>> result = Ref.create(Collections.emptyList());
+    element.accept(new YamlPsiElementVisitor() {
+      @Override
+      public void visitSequence(@NotNull YAMLSequence sequence) {
+        result.set(ContainerUtil.map(sequence.getItems(), i -> new YAMLStructureViewSequenceItem(i, path)));
+      }
+      @Override
+      public void visitMapping(@NotNull YAMLMapping mapping) {
+        result.set(ContainerUtil.map(mapping.getKeyValues(), kv -> new YAMLStructureViewKeyValue(kv, path)));
+      }
+    });
+    return result.get();
   }
 }

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewFile.java

@@ -0,0 +1,49 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.ide.structureView.impl.common.PsiTreeElementBase;
+import com.intellij.navigation.ItemPresentation;
+import com.intellij.util.containers.ContainerUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.yaml.psi.YAMLFile;
+
+import javax.swing.*;
+import java.util.Collection;
+import java.util.Objects;
+
+class YAMLStructureViewFile extends PsiTreeElementBase<YAMLFile> {
+  YAMLStructureViewFile(@NotNull YAMLFile psiElement) {
+    super(psiElement);
+  }
+
+  @NotNull
+  @Override
+  public Collection<StructureViewTreeElement> getChildrenBase() {
+    YAMLFile file = Objects.requireNonNull(getElement());
+    return ContainerUtil.map(file.getDocuments(), YAMLStructureViewDocument::new);
+  }
+
+  @Nullable
+  @Override
+  public String getPresentableText() {
+    return getFilePresentation().getPresentableText();
+  }
+
+  @Nullable
+  public String getLocationString() {
+    return getFilePresentation().getLocationString();
+  }
+
+  @Nullable
+  public Icon getIcon(boolean unused) {
+    return getFilePresentation().getIcon(unused);
+  }
+
+  @NotNull
+  private ItemPresentation getFilePresentation() {
+    YAMLFile file = Objects.requireNonNull(getElement());
+    return Objects.requireNonNull(file.getPresentation());
+  }
+}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewKeyValue.java

@@ -0,0 +1,71 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.util.PlatformIcons;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.yaml.psi.YAMLAlias;
+import org.jetbrains.yaml.psi.YAMLKeyValue;
+import org.jetbrains.yaml.psi.YAMLScalar;
+import org.jetbrains.yaml.psi.YAMLValue;
+
+import javax.swing.*;
+import java.util.Collection;
+import java.util.Objects;
+
+import static org.jetbrains.yaml.structureView.YAMLStructureViewFactory.ALIAS_ICON;
+
+class YAMLStructureViewKeyValue extends DuplicatedPsiTreeElementBase<YAMLKeyValue> {
+  YAMLStructureViewKeyValue(@NotNull YAMLKeyValue kv, String path) {
+    super(kv, path + '.' + kv.getKeyText());
+  }
+
+  @NotNull
+  @Override
+  public Collection<StructureViewTreeElement> getChildrenBase() {
+    return YAMLStructureViewFactory.createChildrenViewTreeElements(getVal(), getDetails());
+  }
+
+  @NotNull
+  public String getPresentableText() {
+    return getKeyValue().getKeyText();
+  }
+
+  @Nullable
+  public String getLocationString() {
+    if (getVal() instanceof YAMLScalar) {
+      return getKeyValue().getValueText();
+    }
+    else if (getVal() instanceof YAMLAlias) {
+      return YAMLStructureViewFactory.getAliasPresentableText((YAMLAlias)getVal());
+    }
+    else {
+      return null;
+    }
+  }
+
+  @Nullable
+  public Icon getIcon(boolean open) {
+    if (getVal() instanceof YAMLScalar) {
+      return getKeyValue().getIcon(0);
+    }
+    else if (getVal() instanceof YAMLAlias) {
+      return ALIAS_ICON;
+    }
+    else {
+      return PlatformIcons.XML_TAG_ICON;
+    }
+  }
+
+  @NotNull
+  private YAMLKeyValue getKeyValue() {
+    return Objects.requireNonNull(getElement());
+  }
+
+  // Base class already has getValue() method with different semantic
+  @Nullable
+  private YAMLValue getVal() {
+    return getKeyValue().getValue();
+  }
+}

plugins/yaml/src/org/jetbrains/yaml/structureView/YAMLStructureViewSequenceItem.java

@@ -0,0 +1,77 @@
+// 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 org.jetbrains.yaml.structureView;
+
+import com.intellij.ide.structureView.StructureViewTreeElement;
+import com.intellij.lang.ASTNode;
+import com.intellij.util.PlatformIcons;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.yaml.YAMLBundle;
+import org.jetbrains.yaml.psi.YAMLAlias;
+import org.jetbrains.yaml.psi.YAMLScalar;
+import org.jetbrains.yaml.psi.YAMLSequenceItem;
+import org.jetbrains.yaml.psi.YAMLValue;
+
+import javax.swing.*;
+import java.util.Collection;
+
+import static org.jetbrains.yaml.structureView.YAMLStructureViewFactory.ALIAS_ICON;
+
+class YAMLStructureViewSequenceItem extends DuplicatedPsiTreeElementBase<YAMLSequenceItem> {
+  YAMLStructureViewSequenceItem(@NotNull YAMLSequenceItem item, String path) {
+    super(item, path + '-' + getItemNumber(item));
+  }
+
+  @NotNull
+  @Override
+  public Collection<StructureViewTreeElement> getChildrenBase() {
+    return YAMLStructureViewFactory.createChildrenViewTreeElements(getItemValue(), getDetails());
+  }
+
+  @NotNull
+  @Override
+  public String getPresentableText() {
+    if (getItemValue() instanceof YAMLScalar) {
+      return ((YAMLScalar)getItemValue()).getTextValue();
+    }
+    else if (getItemValue() instanceof YAMLAlias) {
+      return YAMLStructureViewFactory.getAliasPresentableText((YAMLAlias)getItemValue());
+    }
+    else {
+      return YAMLBundle.message("YAMLStructureViewSequenceItem.element.name");
+    }
+  }
+
+  @Nullable
+  @Override
+  public String getLocationString() {
+    return null;
+  }
+
+  @NotNull
+  @Override
+  public Icon getIcon(boolean unused) {
+    if (getItemValue() instanceof YAMLScalar) {
+      return PlatformIcons.PROPERTY_ICON;
+    }
+    else if (getItemValue() instanceof YAMLAlias) {
+      return ALIAS_ICON;
+    }
+    else {
+      return PlatformIcons.XML_TAG_ICON;
+    }
+  }
+
+  @Nullable
+  private YAMLValue getItemValue() {
+    return getElement().getValue();
+  }
+
+  private static int getItemNumber(@NotNull YAMLSequenceItem item) {
+    int num = 0;
+    for (ASTNode node = item.getNode().getTreePrev(); node != null; node = node.getTreePrev()) {
+      num++;
+    }
+    return num;
+  }
+}

plugins/yaml/testSrc/org/jetbrains/yaml/structure/YAMLStructureTest.java

@@ -0,0 +1,38 @@
+// 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 org.jetbrains.yaml.structure;
+
+import com.intellij.openapi.application.ex.PathManagerEx;
+import com.intellij.testFramework.PlatformTestUtil;
+import com.intellij.testFramework.fixtures.LightPlatformCodeInsightFixtureTestCase;
+import com.intellij.util.ui.tree.TreeUtil;
+import org.jetbrains.yaml.structureView.YAMLAliasResolveNodeProvider;
+
+public class YAMLStructureTest extends LightPlatformCodeInsightFixtureTestCase {
+  @Override
+  protected String getTestDataPath() {
+    return PathManagerEx.getCommunityHomePath() + "/plugins/yaml/testSrc/org/jetbrains/yaml/structure/data/";
+  }
+
+
+  public void testAnchorsAndAliases() {
+    doTest();
+  }
+
+  private void doTest() {
+    String testName = getTestName(true);
+    myFixture.configureByFile(testName + ".yml");
+    doStructureTest(testName, false);
+    doStructureTest(testName, true);
+  }
+
+  private void doStructureTest(String testName, boolean resolveAliases) {
+    myFixture.testStructureView(svc -> {
+      svc.setActionActive(YAMLAliasResolveNodeProvider.ID, resolveAliases);
+      TreeUtil.expandAll(svc.getTree());
+      PlatformTestUtil.waitForPromise(svc.select(svc.getTreeModel().getCurrentEditorElement(), false));
+      String suffix = resolveAliases ? "resolved" : "unresolved";
+      assertSameLinesWithFile(getTestDataPath() + testName + "." + suffix + ".txt",
+                              PlatformTestUtil.print(svc.getTree(), false));
+    });
+  }
+}

plugins/yaml/testSrc/org/jetbrains/yaml/structure/data/anchorsAndAliases.resolved.txt

@@ -0,0 +1,14 @@
+-anchorsAndAliases.yml
+ -YAML document
+  -First occurrence
+   -list
+    item1
+    item2
+  -Second occurrence
+   -list
+    item1
+    item2
+  -Override anchor
+   key
+  -Reuse anchor
+   key

plugins/yaml/testSrc/org/jetbrains/yaml/structure/data/anchorsAndAliases.unresolved.txt

@@ -0,0 +1,10 @@
+-anchorsAndAliases.yml
+ -YAML document
+  -First occurrence
+   -list
+    item1
+    item2
+  Second occurrence
+  -Override anchor
+   key
+  Reuse anchor

plugins/yaml/testSrc/org/jetbrains/yaml/structure/data/anchorsAndAliases.yml

@@ -0,0 +1,8 @@
+First occurrence: &xxx
+  list:
+    - item1
+    - item2
+Second occurrence: *xxx
+Override anchor: &xxx
+  key: val
+Reuse anchor: *xxx