Added reference navigation for observer name

src/com/magento/idea/magento2plugin/indexes/EventIndex.java

@@ -2,6 +2,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+
 package com.magento.idea.magento2plugin.indexes;
 
 import com.intellij.openapi.project.Project;
@@ -13,41 +14,67 @@
 import com.intellij.psi.xml.XmlFile;
 import com.intellij.util.indexing.FileBasedIndex;
 import com.magento.idea.magento2plugin.stubs.indexes.EventNameIndex;
+import com.magento.idea.magento2plugin.stubs.indexes.EventObserverIndex;
 import com.magento.idea.magento2plugin.util.xml.XmlPsiTreeUtil;
-
 import java.util.ArrayList;
 import java.util.Collection;
 
 public class EventIndex {
 
-    private static EventIndex INSTANCE;
-
-    private Project project;
-
-    private EventIndex() {
-    }
-
-    public static EventIndex getInstance(final Project project) {
-        if (null == INSTANCE) {
-            INSTANCE = new EventIndex();
-        }
-        INSTANCE.project = project;
+    private final Project project;
 
-        return INSTANCE;
+    /**
+     * Constructor.
+     */
+    public EventIndex(final Project project) {
+        this.project = project;
     }
 
-    public Collection<PsiElement> getEventElements(final String name, final GlobalSearchScope scope) {
-        Collection<PsiElement> result = new ArrayList<>();
+    /**
+     * Gets event elements by event name.
+     */
+    public Collection<PsiElement> getEventElements(
+            final String name,
+            final GlobalSearchScope scope
+    ) {
+        final Collection<PsiElement> result = new ArrayList<>();
 
-        Collection<VirtualFile> virtualFiles =
+        final Collection<VirtualFile> virtualFiles =
                 FileBasedIndex.getInstance().getContainingFiles(EventNameIndex.KEY, name, scope);
 
-        for (VirtualFile virtualFile : virtualFiles) {
-            XmlFile xmlFile = (XmlFile) PsiManager.getInstance(project).findFile(virtualFile);
-            Collection<XmlAttributeValue> valueElements = XmlPsiTreeUtil
+        for (final VirtualFile virtualFile : virtualFiles) {
+            final XmlFile xmlFile = (XmlFile) PsiManager.getInstance(project).findFile(virtualFile);
+            final Collection<XmlAttributeValue> valueElements = XmlPsiTreeUtil
                     .findAttributeValueElements(xmlFile, "event", "name", name);
             result.addAll(valueElements);
         }
         return result;
     }
+
+    /**
+     * Gets observers by event-observer name combination.
+     */
+    public Collection<PsiElement> getObservers(
+            final String eventName,
+            final String observerName,
+            final GlobalSearchScope scope
+    ) {
+        final Collection<PsiElement> result = new ArrayList<>();
+        final Collection<VirtualFile> virtualFiles
+                = FileBasedIndex.getInstance().getContainingFiles(
+                        EventObserverIndex.KEY, eventName, scope
+                );
+
+        for (final VirtualFile virtualFile: virtualFiles) {
+            final XmlFile eventsXmlFile
+                    = (XmlFile) PsiManager.getInstance(project).findFile(virtualFile);
+            if (eventsXmlFile != null) {
+                result.addAll(
+                        XmlPsiTreeUtil.findObserverTags(eventsXmlFile, eventName, observerName)
+                );
+            }
+        }
+
+        return result;
+    }
 }

src/com/magento/idea/magento2plugin/inspections/xml/ObserverDeclarationInspection.java

@@ -44,6 +44,7 @@ public class ObserverDeclarationInspection extends PhpInspection {
 
     @NotNull
     @Override
+    @SuppressWarnings({"PMD.AvoidInstantiatingObjectsInLoops"})
     public PsiElementVisitor buildVisitor(
             final @NotNull ProblemsHolder problemsHolder,
             final boolean isOnTheFly
@@ -66,12 +67,12 @@ public void visitFile(final PsiFile file) {
                     return;
                 }
 
-                final EventIndex eventIndex = EventIndex.getInstance(file.getProject());
+                final EventIndex eventIndex = new EventIndex(file.getProject());
                 final HashMap<String, XmlTag> targetObserversHash = new HashMap<>();
 
                 for (final XmlTag eventXmlTag: xmlTags) {
                     final HashMap<String, XmlTag> eventProblems = new HashMap<>();
-                    if (!eventXmlTag.getName().equals("event")) {
+                    if (!eventXmlTag.getName().equals(ModuleEventsXml.EVENT_TAG)) {
                         continue;
                     }
 
@@ -236,7 +237,7 @@ private List<XmlTag> fetchObserverTagsFromEventTag(final XmlTag eventXmlTag) {
                 }
 
                 for (final XmlTag observerXmlTag: observerXmlTags) {
-                    if (!observerXmlTag.getName().equals("observer")) {
+                    if (!observerXmlTag.getName().equals(ModuleEventsXml.OBSERVER_TAG)) {
                         continue;
                     }
 
@@ -257,10 +258,11 @@ private void addModuleNameWhereSameObserverUsed(
                     return;
                 }
 
-                if (!moduleDeclarationTag.getName().equals("module")) {
+                if (!moduleDeclarationTag.getName().equals(ModuleEventsXml.MODULE_TAG)) {
                     return;
                 }
-                final XmlAttribute moduleNameAttribute = moduleDeclarationTag.getAttribute("name");
+                final XmlAttribute moduleNameAttribute
+                        = moduleDeclarationTag.getAttribute(ModuleEventsXml.NAME_ATTRIBUTE);
                 if (moduleNameAttribute == null) {
                     return;
                 }

src/com/magento/idea/magento2plugin/magento/files/ModuleEventsXml.java

@@ -19,6 +19,10 @@ public class ModuleEventsXml implements ModuleFileInterface {
     public static final String OBSERVER_TAG = "observer";
     public static final String INSTANCE_ATTRIBUTE = "instance";
     public static final String EVENT_TAG = "event";
+    public static final String MODULE_TAG = "module";
+
+    //attributes
+    public static final String NAME_ATTRIBUTE = "name";
 
     private static final ModuleEventsXml INSTANCE = new ModuleEventsXml();
 

src/com/magento/idea/magento2plugin/reference/provider/EventDispatchReferenceProvider.java

@@ -29,7 +29,7 @@ public PsiReference[] getReferencesByElement(
     ) {
         final String value = StringUtil.unquoteString(element.getText());
         final List<PsiReference> psiReferences = new ArrayList<>();
-        final Collection<PsiElement> targets = EventIndex.getInstance(element.getProject())
+        final Collection<PsiElement> targets = new EventIndex(element.getProject())
                 .getEventElements(
                         value,
                         GlobalSearchScope.getScopeRestrictedByFileTypes(

src/com/magento/idea/magento2plugin/reference/provider/ObserverNameReferenceProvider.java

@@ -0,0 +1,43 @@
+package com.magento.idea.magento2plugin.reference.provider;
+
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiReference;
+import com.intellij.psi.PsiReferenceProvider;
+import com.intellij.psi.impl.source.xml.XmlAttributeValueImpl;
+import com.intellij.psi.impl.source.xml.XmlTagImpl;
+import com.intellij.psi.search.GlobalSearchScope;
+import com.intellij.util.ProcessingContext;
+import com.magento.idea.magento2plugin.indexes.EventIndex;
+import com.magento.idea.magento2plugin.reference.xml.PolyVariantReferenceBase;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import org.jetbrains.annotations.NotNull;
+
+public class ObserverNameReferenceProvider extends PsiReferenceProvider {
+    @Override
+    public PsiReference @NotNull [] getReferencesByElement(
+            @NotNull final PsiElement element,
+            @NotNull final ProcessingContext context
+    ) {
+        final List<PsiReference> psiReferences = new ArrayList<>();
+        final XmlTagImpl eventTag = (XmlTagImpl) element.getParent().getParent().getParent();
+        final String eventName = eventTag.getAttributeValue("name");
+
+        if (eventName == null) {
+            return psiReferences.toArray(new PsiReference[0]);
+        }
+
+        final String observerName = ((XmlAttributeValueImpl) element).getValue();
+        final Collection<PsiElement> observers
+                = new EventIndex(element.getProject()).getObservers(
+                        eventName, observerName, GlobalSearchScope.allScope(element.getProject())
+                );
+
+        if (!observers.isEmpty()) {
+            psiReferences.add(new PolyVariantReferenceBase(element, observers));
+        }
+
+        return psiReferences.toArray(new PsiReference[0]);
+    }
+}

src/com/magento/idea/magento2plugin/reference/xml/XmlReferenceContributor.java

@@ -153,6 +153,16 @@ public void registerReferenceProviders(@NotNull PsiReferenceRegistrar registrar)
             new EventNameReferenceProvider()
         );
 
+        // <observer name="reference" />
+        registrar.registerReferenceProvider(
+                XmlPatterns.xmlAttributeValue().withParent(
+                        XmlPatterns.xmlAttribute().withName("name").withParent(
+                                XmlPatterns.xmlTag().withName("observer")
+                        )
+                ),
+                new ObserverNameReferenceProvider()
+        );
+
         // <someXmlTag someAttribute="Module_Name[.*]" />
         registrar.registerReferenceProvider(
             XmlPatterns.xmlAttributeValue().withValue(string().matches(".*[A-Z][a-zA-Z0-9]+_[A-Z][a-zA-Z0-9]+.*")),

src/com/magento/idea/magento2plugin/util/xml/XmlPsiTreeUtil.java

@@ -29,6 +29,10 @@
         "PMD.UseObjectForClearerAPI"
 })
 public class XmlPsiTreeUtil {
+    public static final String EVENT_TAG_NAME = "event";
+    public static final String OBSERVER_TAG_NAME = "observer";
+    public static final String NAME_ATTRIBUTE = "name";
+
     /**
      * Get type tag of an argument.
      *
@@ -47,6 +51,52 @@ public static XmlTag getTypeTagOfArgument(final XmlElement psiArgumentValueEleme
         return PsiTreeUtil.getParentOfType(argumentsTag, XmlTag.class);
     }
 
+    /**
+     * Finds observer tags by event-observer name combination.
+     */
+    @SuppressWarnings({
+            "PMD.CyclomaticComplexity"
+    })
+    public static Collection<XmlAttributeValue> findObserverTags(
+            final XmlFile xmlFile,
+            final String eventName,
+            final String observerName
+    ) {
+        Collection<XmlAttributeValue> psiElements = new THashSet<>();
+        final XmlTag configTag = xmlFile.getRootTag();
+
+        if (configTag == null) {
+            return psiElements;
+        }
+
+        /* Loop through event tags */
+        for (XmlTag eventTag: configTag.getSubTags()) {
+            XmlAttribute eventNameAttribute = eventTag.getAttribute(NAME_ATTRIBUTE);
+
+            /* Check if event tag and name matches */
+            if (EVENT_TAG_NAME.equals(eventTag.getName())
+                    && eventNameAttribute != null
+                    && eventName.equals(eventNameAttribute.getValue())
+            ) {
+                /* Loop through observer tags under matched event tag */
+                for (XmlTag observerTag: eventTag.getSubTags()) {
+                    XmlAttribute observerNameAttribute = observerTag.getAttribute(NAME_ATTRIBUTE);
+
+                    /* Check if observer tag and name matches */
+                    if (OBSERVER_TAG_NAME.equals(observerTag.getName())
+                            && observerNameAttribute != null
+                            && observerNameAttribute.getValueElement() != null
+                            && observerName.equals(observerNameAttribute.getValue())
+                    ) {
+                        psiElements.add(observerNameAttribute.getValueElement());
+                    }
+                }
+            }
+        }
+
+        return psiElements;
+    }
+
     /**
      * Find attribute value elements based on the tag name.
      *

testData/project/magento2/vendor/magento/module-catalog/etc/events.xml

@@ -5,8 +5,8 @@
   * See COPYING.txt for license details.
   */
 -->
-
-<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
     <event name="test_event_in_test_class">
         <observer name="test_observer" instance="Magento\Catalog\Observer\TestObserver" />
     </event>

testData/reference/xml/ObserverReferenceRegistrar/observerNameMustHaveReference/events.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ /**
+  * Copyright © Magento, Inc. All rights reserved.
+  * See COPYING.txt for license details.
+  */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
+    <event name="test_event_in_test_class">
+        <observer name="test_observer<caret>" disabled="true"/>
+    </event>
+</config>

tests/com/magento/idea/magento2plugin/reference/BaseReferenceTestCase.java

@@ -39,13 +39,29 @@ protected void setUp() throws Exception {
     protected void assertHasReferenceToXmlAttributeValue(final String reference) {
         final PsiElement element = getElementFromCaret();
         for (final PsiReference psiReference: element.getReferences()) {
-            final PsiElement resolved = psiReference.resolve();
-            if (!(resolved instanceof XmlAttributeValue)) {
-                continue;
-            }
+            if (psiReference instanceof PolyVariantReferenceBase) {
+                final ResolveResult[] resolveResults
+                        = ((PolyVariantReferenceBase) psiReference).multiResolve(true);
 
-            if (((XmlAttributeValue) resolved).getValue().equals(reference)) {
-                return;
+                for (final ResolveResult resolveResult : resolveResults) {
+                    final PsiElement resolved = resolveResult.getElement();
+                    if (!(resolved instanceof XmlAttributeValue)) {
+                        continue;
+                    }
+
+                    if (((XmlAttributeValue) resolved).getValue().equals(reference)) {
+                        return;
+                    }
+                }
+            } else {
+                final PsiElement resolved = psiReference.resolve();
+                if (!(resolved instanceof XmlAttributeValue)) {
+                    continue;
+                }
+
+                if (((XmlAttributeValue) resolved).getValue().equals(reference)) {
+                    return;
+                }
             }
         }
         final String referenceNotFound =

tests/com/magento/idea/magento2plugin/reference/xml/ObserverReferenceRegistrarTest.java

@@ -27,6 +27,15 @@ public void testObserverInstanceDirectorySnakeCaseMustHaveReference() {
         assertHasReferencePhpClass("Magento\\Catalog\\test_event\\TestObserver");
     }
 
+    /**
+     * Tests for observer name reference in events.xml.
+     */
+    public void testObserverNameMustHaveReference() {
+        myFixture.configureByFile(this.getFixturePath(ModuleEventsXml.FILE_NAME));
+
+        assertHasReferenceToXmlAttributeValue("test_observer");
+    }
+
     /**
      * Tests for event name reference in events.xml.
      */