[javadoc] Add completion for fragment references

#IDEA-376337

GitOrigin-RevId: 887853966d3bea20f27f3d9f70d1c045176dc538

java/java-impl/src/com/intellij/codeInsight/completion/JavaDocCompletionContributor.java

@@ -7,6 +7,8 @@ import com.intellij.codeInsight.completion.scope.JavaCompletionProcessor;
 import com.intellij.codeInsight.editorActions.wordSelection.DocTagSelectioner;
 import com.intellij.codeInsight.javadoc.JavaDocUtil;
 import com.intellij.codeInsight.javadoc.SnippetMarkup;
+import com.intellij.codeInsight.javadoc.index.JavaDocFragmentAnchorCacheKt;
+import com.intellij.codeInsight.javadoc.index.JavaDocFragmentData;
 import com.intellij.codeInsight.lookup.*;
 import com.intellij.codeInsight.template.TemplateManager;
 import com.intellij.codeInsight.template.impl.ConstantNode;
@@ -15,6 +17,7 @@ import com.intellij.codeInspection.InspectionProfile;
 import com.intellij.codeInspection.SuppressionUtilCore;
 import com.intellij.codeInspection.javaDoc.JavadocDeclarationInspection;
 import com.intellij.codeInspection.javaDoc.MissingJavadocInspection;
+import com.intellij.icons.AllIcons;
 import com.intellij.java.syntax.parser.JavaKeywords;
 import com.intellij.lang.Language;
 import com.intellij.lang.java.JavaLanguage;
@@ -35,6 +38,8 @@ import com.intellij.psi.codeStyle.CodeStyleSettings;
 import com.intellij.psi.codeStyle.JavaCodeStyleManager;
 import com.intellij.psi.filters.TrueFilter;
 import com.intellij.psi.impl.JavaConstantExpressionEvaluator;
+import com.intellij.psi.impl.source.javadoc.PsiDocFragmentName;
+import com.intellij.psi.impl.source.javadoc.PsiDocFragmentRef;
 import com.intellij.psi.impl.source.javadoc.PsiDocMethodOrFieldRef;
 import com.intellij.psi.impl.source.javadoc.PsiDocParamRef;
 import com.intellij.psi.javadoc.*;
@@ -131,6 +136,16 @@ public final class JavaDocCompletionContributor extends CompletionContributor im
 
           JavaCompletionContributor.addAllClasses(parameters, result, new JavaCompletionSession(result));
         }
+        else if (position.getParent() instanceof PsiDocFragmentName docFragmentName) {
+          final PsiElement parent = docFragmentName.getParent();
+          final PsiClass classRef = parent instanceof PsiDocFragmentRef ? ((PsiDocFragmentRef)docFragmentName.getParent()).getScope() : null;
+          final String fqn = classRef == null ? null : classRef.getQualifiedName();
+          if (fqn != null) {
+            for (JavaDocFragmentData anchor : JavaDocFragmentAnchorCacheKt.getAnchors(position.getProject(), fqn)) {
+              result.addElement(LookupElementBuilder.create(anchor.getName()).withIcon(AllIcons.Nodes.Related));
+            }
+          }
+        }
 
         if (tag != null && "author".equals(tag.getName())) {
           result.addElement(LookupElementBuilder.create(SystemProperties.getUserName()));
@@ -268,6 +283,12 @@ public final class JavaDocCompletionContributor extends CompletionContributor im
   @Override
   public void fillCompletionVariants(@NotNull CompletionParameters parameters, @NotNull CompletionResultSet result) {
     PsiElement position = parameters.getPosition();
+
+    if (position.getParent() instanceof PsiDocFragmentName) {
+      super.fillCompletionVariants(parameters, result);
+      return;
+    }
+
     if (PsiDocToken.isDocToken(position, JavaDocTokenType.DOC_TAG_VALUE_TOKEN)) {
       PsiElement parent = position.getParent();
       if (parent instanceof PsiDocTagValue && !(parent instanceof PsiDocParamRef) && !(parent instanceof PsiDocMethodOrFieldRef)) {

java/java-psi-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocFragmentRef.java

@@ -2,11 +2,13 @@
 package com.intellij.psi.impl.source.javadoc;
 
 import com.intellij.psi.JavaElementVisitor;
+import com.intellij.psi.PsiClass;
 import com.intellij.psi.PsiElementVisitor;
 import com.intellij.psi.impl.source.Constants;
 import com.intellij.psi.impl.source.tree.CompositePsiElement;
 import com.intellij.psi.javadoc.PsiDocTagValue;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 public class PsiDocFragmentRef extends CompositePsiElement implements PsiDocTagValue, Constants {
   public PsiDocFragmentRef() {
@@ -22,4 +24,8 @@ public class PsiDocFragmentRef extends CompositePsiElement implements PsiDocTagV
       visitor.visitElement(this);
     }
   }
+
+  public @Nullable PsiClass getScope() {
+    return PsiDocMethodOrFieldRef.getScope(this);
+  }
 }

java/java-psi-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocMethodOrFieldRef.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+// Copyright 2000-2025 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
 package com.intellij.psi.impl.source.javadoc;
 
 import com.intellij.lang.ASTNode;
@@ -151,9 +151,17 @@ public class PsiDocMethodOrFieldRef extends CompositePsiElement implements PsiDo
     return ArrayUtilRt.toStringArray(types);
   }
 
-  private @Nullable PsiClass getScope(){
-    if (getFirstChildNode().getElementType() == JavaDocElementType.DOC_REFERENCE_HOLDER) {
-      final PsiElement firstChildPsi = SourceTreeToPsiMap.treeElementToPsi(getFirstChildNode().getFirstChildNode());
+  private @Nullable PsiClass getScope() {
+    return getScope(this);
+  }
+
+  /**
+   * Returns the PsiClass targeted by the given reference element (e.g. {@code MyClass#…} or {@code MyClass##…}).
+   */
+  public static @Nullable PsiClass getScope(CompositePsiElement ref) {
+    final TreeElement firstChildNode = ref.getFirstChildNode();
+    if (firstChildNode != null && firstChildNode.getElementType() == DOC_REFERENCE_HOLDER) {
+      final PsiElement firstChildPsi = SourceTreeToPsiMap.treeElementToPsi(firstChildNode.getFirstChildNode());
       if (firstChildPsi instanceof PsiJavaCodeReferenceElement) {
         PsiJavaCodeReferenceElement referenceElement = (PsiJavaCodeReferenceElement)firstChildPsi;
         final PsiElement referencedElement = referenceElement.resolve();
@@ -164,15 +172,16 @@ public class PsiDocMethodOrFieldRef extends CompositePsiElement implements PsiDo
         final PsiKeyword keyword = (PsiKeyword)firstChildPsi;
 
         if (keyword.getTokenType().equals(THIS_KEYWORD)) {
-          return JavaResolveUtil.getContextClass(this);
-        } else if (keyword.getTokenType().equals(SUPER_KEYWORD)) {
-          final PsiClass contextClass = JavaResolveUtil.getContextClass(this);
+          return JavaResolveUtil.getContextClass(ref);
+        }
+        else if (keyword.getTokenType().equals(SUPER_KEYWORD)) {
+          final PsiClass contextClass = JavaResolveUtil.getContextClass(ref);
           if (contextClass != null) return contextClass.getSuperClass();
           return null;
         }
       }
     }
-    return JavaResolveUtil.getContextClass(this);
+    return JavaResolveUtil.getContextClass(ref);
   }
 
   public static PsiMethod @NotNull [] findMethods(@Nullable MethodSignature methodSignature,

java/java-tests/testData/codeInsight/completion/javadoc/See7.java

@@ -0,0 +1,25 @@
+/**
+ * @see ##<caret>
+ */
+class C {
+  private int myField;
+
+  /**
+   * <p id=my-id1></p>
+   */
+  public void foo1() {}
+
+  /**
+   * <p id='my-id2'></p>
+   */
+  public void foo2() {}
+
+  /**
+   * <h1 id="my-id3"></h1>
+   */
+  public void foo3() {}
+
+  /// <div id="my-id4"></div>
+  public void foo4() {}
+
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/completion/JavadocCompletionTest.java

@@ -138,6 +138,12 @@ public class JavadocCompletionTest extends LightFixtureCompletionTestCase {
     assertTrue(getLookupElementStrings().containsAll(Arrays.asList("foo", "myName")));
   }
 
+  @NeedsIndex.Full
+  public void testSee7() {
+    configureByFile("See7.java");
+    assertTrue(getLookupElementStrings().containsAll(Arrays.asList("my-id1", "my-id2", "my-id3", "my-id4")));
+  }
+
   @NeedsIndex.ForStandardLibrary
   public void testIDEADEV10620() {
     configureByFile("IDEADEV10620.java");