[java-completion] IDEA-251394 Smart completion suggests Collections.emptyList() twice

GitOrigin-RevId: 212118424fd3418a91a969cec6a275f23aa64c8e

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

@@ -5,6 +5,7 @@ import com.intellij.codeInsight.lookup.AutoCompletionPolicy;
 import com.intellij.codeInsight.lookup.LookupElement;
 import com.intellij.psi.*;
 import com.intellij.util.Consumer;
+import com.intellij.util.ObjectUtils;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
 
@@ -35,6 +36,19 @@ class CollectionsUtilityMethodsProvider {
     final PsiClass collectionsClass =
         JavaPsiFacade.getInstance(myElement.getProject()).findClass(JAVA_UTIL_COLLECTIONS, myElement.getResolveScope());
     if (collectionsClass == null) return;
+    PsiJavaFile file = ObjectUtils.tryCast(parent.getContainingFile(), PsiJavaFile.class);
+    if (file == null) return;
+    PsiImportList importList = file.getImportList();
+    if (importList != null) {
+      for (PsiImportStaticStatement statement : importList.getImportStaticStatements()) {
+        PsiClass aClass = statement.resolveTargetClass();
+        if (aClass != null && aClass.isEquivalentTo(collectionsClass)) {
+          // The Collections class is already statically imported;
+          // should be suggested anyway in JavaStaticMemberProcessor
+          return;
+        }
+      }
+    }
 
     final PsiElement pparent = parent.getParent();
     if (showAll ||

java/java-tests/testData/codeInsight/completion/smartType/NoDuplicateEmptyList.java

@@ -0,0 +1,23 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static java.util.Collections.singletonList;
+
+// IDEA-251394
+public final class SomeUtils {
+
+    private SomeUtils() {}
+
+    public static List<Integer> getEventsFor(List<String> execution) {
+        List<Long> statuses = new ArrayList<>();
+        if (statuses.isEmpty()) {
+            return <caret>
+        }
+
+        if (execution.size() > 1) {
+            return Collections.emptyList();
+        }
+        return new ArrayList<>();
+    }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartType18CompletionTest.java

@@ -346,4 +346,11 @@ public class SmartType18CompletionTest extends LightFixtureCompletionTestCase {
   public void testFilterInaccessibleConstructors() { doAntiTest(); }
 
   public void testCastInToArrayCallWithUnresolvedType() { doAntiTest(); }
+
+  @NeedsIndex.ForStandardLibrary
+  public void testNoDuplicateEmptyList() {
+    configureByTestName();
+    Lookup lookup = getLookup();
+    assertEquals(1, lookup.getItems().stream().filter(item -> item.getLookupString().equals("emptyList")).count());
+  }
 }