deprecate EmptyIterable in favor of standard Collections.emptyList()

GitOrigin-RevId: e0e211241eb48f665a3117627c81f0c67fff0883

java/java-psi-api/src/com/intellij/psi/util/PsiUtil.java

@@ -28,7 +28,6 @@ import com.intellij.psi.tree.TokenSet;
 import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.TimeoutUtil;
 import com.intellij.util.containers.ContainerUtil;
-import com.intellij.util.containers.EmptyIterable;
 import com.intellij.util.containers.JBIterable;
 import org.intellij.lang.annotations.MagicConstant;
 import org.jetbrains.annotations.Contract;
@@ -988,7 +987,7 @@ public final class PsiUtil extends PsiUtilCore {
       currentOwner = currentOwner.getContainingClass();
     }
 
-    if (result == null) return EmptyIterable.getInstance();
+    if (result == null) return Collections.emptyList();
     return result;
   }
 

platform/lang-impl/src/com/intellij/codeInsight/hints/MethodInfoBlacklistFilter.java

@@ -24,6 +24,7 @@ import com.intellij.lang.Language;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -60,13 +61,13 @@ public class MethodInfoBlacklistFilter implements HintInfoFilter {
   private static Set<String> fullBlacklist(Language language) {
     InlayParameterHintsProvider provider = InlayParameterHintsExtension.INSTANCE.forLanguage(language);
     if (provider == null) {
-      return ContainerUtil.newHashOrEmptySet(ContainerUtil.emptyIterable());
+      return Collections.emptySet();
     }
 
     Set<String> blackList = blacklist(language);
     Language dependentLanguage = provider.getBlackListDependencyLanguage();
     if (dependentLanguage != null) {
-      blackList.addAll(blacklist(dependentLanguage));
+      blackList = ContainerUtil.union(blackList, blacklist(dependentLanguage));
     }
     return blackList;
   }
@@ -79,7 +80,7 @@ public class MethodInfoBlacklistFilter implements HintInfoFilter {
       Diff diff = settings.getBlackListDiff(getLanguageForSettingKey(language));
       return diff.applyOn(provider.getDefaultBlackList());
     }
-    return ContainerUtil.newHashOrEmptySet(ContainerUtil.emptyIterable());
+    return Collections.emptySet();
   }
 
 }

platform/platform-impl/src/com/intellij/openapi/vfs/newvfs/impl/VirtualFileImpl.java

@@ -37,7 +37,6 @@ import com.intellij.openapi.vfs.newvfs.NewVirtualFile;
 import com.intellij.openapi.vfs.newvfs.NewVirtualFileSystem;
 import com.intellij.util.LineSeparator;
 import com.intellij.util.ObjectUtils;
-import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.io.UnsyncByteArrayInputStream;
 import com.intellij.util.keyFMap.KeyFMap;
 import org.jetbrains.annotations.NonNls;
@@ -71,7 +70,7 @@ public class VirtualFileImpl extends VirtualFileSystemEntry {
   @NotNull
   @Override
   public Iterable<VirtualFile> iterInDbChildren() {
-    return ContainerUtil.emptyIterable();
+    return Collections.emptyList();
   }
 
   @Override

platform/platform-impl/src/com/intellij/xml/breadcrumbs/BreadcrumbsPanel.java

@@ -32,7 +32,6 @@ import com.intellij.ui.DirtyUI;
 import com.intellij.ui.Gray;
 import com.intellij.ui.components.breadcrumbs.Crumb;
 import com.intellij.util.concurrency.NonUrgentExecutor;
-import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.ui.MouseEventAdapter;
 import com.intellij.util.ui.UIUtil;
 import com.intellij.util.ui.update.MergingUpdateQueue;
@@ -50,6 +49,7 @@ import java.awt.event.MouseEvent;
 import java.beans.PropertyChangeEvent;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import static com.intellij.openapi.diagnostic.Logger.getInstance;
@@ -83,7 +83,7 @@ public abstract class BreadcrumbsPanel extends JComponent implements Disposable
   };
 
   private static final Key<BreadcrumbsPanel> BREADCRUMBS_COMPONENT_KEY = new Key<>("BREADCRUMBS_KEY");
-  private static final Iterable<? extends Crumb> EMPTY_BREADCRUMBS = ContainerUtil.emptyIterable();
+  private static final Iterable<? extends Crumb> EMPTY_BREADCRUMBS = Collections.emptyList();
 
   public BreadcrumbsPanel(@NotNull final Editor editor) {
     myEditor = editor;

platform/platform-impl/src/com/intellij/xml/breadcrumbs/PsiFileBreadcrumbsCollector.java

@@ -22,10 +22,7 @@ import com.intellij.util.text.CharArrayUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.LinkedList;
-import java.util.PriorityQueue;
+import java.util.*;
 
 import static com.intellij.xml.breadcrumbs.BreadcrumbsUtilEx.findProvider;
 
@@ -99,7 +96,7 @@ public class PsiFileBreadcrumbsCollector extends FileBreadcrumbsCollector {
     Collection<Pair<PsiElement, BreadcrumbsProvider>> pairs =
       getLineElements(document, offset, file, myProject, defaultInfoProvider, true);
 
-    if (pairs == null) return ContainerUtil.emptyIterable();
+    if (pairs == null) return Collections.emptyList();
 
     ArrayList<Crumb> result = new ArrayList<>(pairs.size());
     CrumbPresentation[] presentations = getCrumbPresentations(toPsiElementArray(pairs));

platform/util/src/com/intellij/util/containers/ContainerUtil.java

@@ -337,8 +337,8 @@ public class ContainerUtil extends ContainerUtilRt {
   }
 
   /**
-    * @deprecated Use {@link SmartList(T)}
-    */
+   * @deprecated Use {@link SmartList(T)}
+   */
   @SafeVarargs
   @NotNull
   @Contract(pure=true)
@@ -944,10 +944,14 @@ public class ContainerUtil extends ContainerUtilRt {
     return Collections.emptyIterator();
   }
 
+  /**
+   * @deprecated Use {@link Collections#emptyList()} instead
+   */
   @NotNull
+  @Deprecated
   @Contract(pure=true)
   public static <T> Iterable<T> emptyIterable() {
-    return EmptyIterable.getInstance();
+    return Collections.emptyList();
   }
 
   @Contract(pure=true)
@@ -1301,7 +1305,7 @@ public class ContainerUtil extends ContainerUtilRt {
   @NotNull
   @Contract(pure=true)
   public static <T> Iterable<T> iterate(@NotNull final Collection<? extends T> collection, @NotNull final Condition<? super T> condition) {
-    if (collection.isEmpty()) return emptyIterable();
+    if (collection.isEmpty()) return Collections.emptyList();
     return () -> new Iterator<T>() {
       private final Iterator<? extends T> impl = collection.iterator();
       private T next = findNext();
@@ -1605,7 +1609,7 @@ public class ContainerUtil extends ContainerUtilRt {
   @NotNull
   @Contract(pure=true)
   public static <T> Iterable<T> concat(final Iterable<? extends T> @NotNull ... iterables) {
-    if (iterables.length == 0) return emptyIterable();
+    if (iterables.length == 0) return Collections.emptyList();
     if (iterables.length == 1) {
       //noinspection unchecked
       return (Iterable<T>)iterables[0];
@@ -2345,25 +2349,6 @@ public class ContainerUtil extends ContainerUtilRt {
     return count;
   }
 
-  @NotNull
-  @Contract(pure=true)
-  public static <T> List<T> unfold(@Nullable T t, @NotNull NullableFunction<? super T, ? extends T> next) {
-    if (t == null) return emptyList();
-
-    List<T> list = new ArrayList<>();
-    while (t != null) {
-      list.add(t);
-      t = next.fun(t);
-    }
-    return list;
-  }
-
-  @NotNull
-  @Contract(pure=true)
-  public static <T> List<T> dropTail(@NotNull List<T> items) {
-    return items.subList(0, items.size() - 1);
-  }
-
   /**
    * @deprecated Use {@link Arrays#asList(Object[])}
    */

platform/util/src/com/intellij/util/containers/EmptyIterable.java

@@ -20,6 +20,10 @@ import org.jetbrains.annotations.NotNull;
 import java.util.Collections;
 import java.util.Iterator;
 
+/**
+ * @deprecated Use {@link Collections#emptyList()} instead
+ */
+@Deprecated
 public class EmptyIterable<T> implements Iterable<T> {
   private static final EmptyIterable INSTANCE = new EmptyIterable();
 

plugins/maven/src/main/java/org/jetbrains/idea/maven/plugins/groovy/MavenGroovyPolyglotPomMemberContributor.java

@@ -265,7 +265,7 @@ public class MavenGroovyPolyglotPomMemberContributor extends NonCodeMembersContr
 
     if (!methodCallInfo.isEmpty() &&
         StringUtil.endsWithIgnoreCase(ContainerUtil.getLastItem(methodCallInfo), CompletionUtilCore.DUMMY_IDENTIFIER_TRIMMED)) {
-      key = StringUtil.join(ContainerUtil.dropTail(methodCallInfo), "->");
+      key = StringUtil.join(methodCallInfo.subList(0, methodCallInfo.size() - 1), "->");
       for (String classSource : multiMap.get(key)) {
         DynamicMemberUtils.process(processor, false, place, classSource);
       }