IDEA-66243 Support moving caret in lookups as in JB

java/java-tests/testSrc/com/intellij/codeInsight/completion/JavaAutoPopupTest.groovy

@@ -539,5 +539,37 @@ public interface Test {
 
   }
 
+  public void testLeftRightMovements() {
+    myFixture.configureByText("a.java", """
+      class Foo {
+        void foo(String iterable) {
+          <caret>ter
+        }
+      }
+    """)
+    type('i')
+    def offset = myFixture.editor.caretModel.offset
+    assertSameElements myFixture.lookupElementStrings, "if", "iterable", "int"
+
+    edt { myFixture.performEditorAction(IdeActions.ACTION_EDITOR_MOVE_CARET_RIGHT) }
+    assert myFixture.editor.caretModel.offset == offset + 1
+    assertOrderedEquals myFixture.lookupElementStrings, "iterable"
+    assertEquals 'iterable', lookup.currentItem.lookupString
+
+    edt { myFixture.performEditorAction(IdeActions.ACTION_EDITOR_MOVE_CARET_LEFT) }
+    assert myFixture.editor.caretModel.offset == offset
+    assertSameElements myFixture.lookupElementStrings, "if", "iterable", "int"
+    assertEquals 'iterable', lookup.currentItem.lookupString
+
+    edt { myFixture.performEditorAction(IdeActions.ACTION_EDITOR_MOVE_CARET_LEFT) }
+    joinAlarm()
+    joinCompletion()
+    assert lookup.items.size() > 3
+
+    for (i in 0.."iter".size()) {
+      edt { myFixture.performEditorAction(IdeActions.ACTION_EDITOR_MOVE_CARET_RIGHT) }
+    }
+    assert !lookup
+  }
 
 }

platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/BackspaceHandler.java

@@ -37,10 +37,15 @@ public class BackspaceHandler extends EditorActionHandler {
       return;
     }
 
+    truncatePrefix(dataContext, lookup, myOriginalHandler, lookup.getLookupStart());
+  }
+
+  static void truncatePrefix(final DataContext dataContext, LookupImpl lookup, final EditorActionHandler handler, final int hideOffset) {
+    final Editor editor = lookup.getEditor();
     lookup.performGuardedChange(new Runnable() {
       @Override
       public void run() {
-        myOriginalHandler.execute(editor, dataContext);
+        handler.execute(editor, dataContext);
       }
     });
 
@@ -49,7 +54,7 @@ public class BackspaceHandler extends EditorActionHandler {
       return;
     }
 
-    if (lookup.getLookupStart() < editor.getCaretModel().getOffset()) {
+    if (hideOffset < editor.getCaretModel().getOffset()) {
       if (process != null) {
         process.scheduleRestart();
         return;

platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/LookupActionHandler.java

@@ -17,6 +17,8 @@
 package com.intellij.codeInsight.lookup.impl;
 
 import com.intellij.codeInsight.completion.CompletionProgressIndicator;
+import com.intellij.codeInsight.completion.impl.CompletionServiceImpl;
+import com.intellij.codeInsight.lookup.CharFilter;
 import com.intellij.codeInsight.lookup.Lookup;
 import com.intellij.codeInsight.lookup.LookupManager;
 import com.intellij.ide.ui.UISettings;
@@ -185,4 +187,51 @@ public abstract class LookupActionHandler extends EditorActionHandler {
     }
   }
 
+  public static class LeftHandler extends LookupActionHandler {
+    public LeftHandler(EditorActionHandler originalHandler) {
+      super(originalHandler, false);
+    }
+
+    @Override
+    protected void executeInLookup(LookupImpl lookup, DataContext context) {
+      BackspaceHandler.truncatePrefix(context, lookup, myOriginalHandler, lookup.getLookupStart() - 1);
+    }
+  }
+  public static class RightHandler extends LookupActionHandler {
+    public RightHandler(EditorActionHandler originalHandler) {
+      super(originalHandler, false);
+    }
+
+    @Override
+    protected void executeInLookup(LookupImpl lookup, DataContext context) {
+      final Editor editor = lookup.getEditor();
+      final int offset = editor.getCaretModel().getOffset();
+      CharSequence seq = editor.getDocument().getCharsSequence();
+      if (seq.length() <= offset) {
+        myOriginalHandler.execute(editor, context);
+        return;
+      }
+
+      char c = seq.charAt(offset);
+      CharFilter.Result lookupAction = TypedHandler.getLookupAction(c, lookup);
+      if (lookupAction != CharFilter.Result.ADD_TO_PREFIX || Character.isWhitespace(c)) {
+        myOriginalHandler.execute(editor, context);
+        return;
+      }
+
+      lookup.performGuardedChange(new Runnable() {
+        @Override
+        public void run() {
+          editor.getCaretModel().moveToOffset(offset + 1);
+        }
+      });
+
+      lookup.appendPrefix(c);
+      final CompletionProgressIndicator completion = CompletionServiceImpl.getCompletionService().getCurrentCompletion();
+      if (completion != null) {
+        completion.prefixUpdated();
+      }
+    }
+  }
+
 }

platform/lang-impl/src/com/intellij/codeInsight/lookup/impl/TypedHandler.java

@@ -26,10 +26,8 @@ import com.intellij.codeInsight.lookup.LookupElement;
 import com.intellij.codeInsight.lookup.LookupManager;
 import com.intellij.featureStatistics.FeatureUsageTracker;
 import com.intellij.openapi.actionSystem.DataContext;
-import com.intellij.openapi.command.CommandProcessor;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
-import com.intellij.openapi.editor.EditorBundle;
 import com.intellij.openapi.editor.EditorModificationUtil;
 import com.intellij.openapi.editor.actionSystem.TypedActionHandler;
 import com.intellij.openapi.extensions.Extensions;
@@ -55,8 +53,7 @@ public class TypedHandler implements TypedActionHandler {
         return;
       }
 
-      final LookupElement currentItem = lookup.getCurrentItem();
-      final CharFilter.Result result = getLookupAction(charTyped, currentItem, lookup);
+      final CharFilter.Result result = getLookupAction(charTyped, lookup);
       lookup.performGuardedChange(new Runnable() {
         public void run() {
           EditorModificationUtil.deleteSelectedText(editor);
@@ -99,7 +96,8 @@ public class TypedHandler implements TypedActionHandler {
     }
   }
 
-  private static CharFilter.Result getLookupAction(final char charTyped, final LookupElement currentItem, final LookupImpl lookup) {
+  static CharFilter.Result getLookupAction(final char charTyped, final LookupImpl lookup) {
+    final LookupElement currentItem = lookup.getCurrentItem();
     if (currentItem != null && charTyped != ' ') {
       String postfix = lookup.getAdditionalPrefix() + charTyped;
       final PrefixMatcher matcher = currentItem.getPrefixMatcher();

platform/platform-resources/src/META-INF/LangExtensions.xml

@@ -493,6 +493,8 @@
   <editorActionHandler action="EditorDown" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$DownHandler"/>
   <editorActionHandler action="EditorPageUp" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$PageUpHandler"/>
   <editorActionHandler action="EditorPageDown" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$PageDownHandler"/>
+  <editorActionHandler action="EditorLeft" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$LeftHandler"/>
+  <editorActionHandler action="EditorRight" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$RightHandler"/>
   <editorActionHandler action="EditorLineStart" implementationClass="com.intellij.codeInsight.lookup.impl.HomeHandler"/>
   <editorActionHandler action="EditorLineEnd" implementationClass="com.intellij.codeInsight.lookup.impl.EndHandler"/>
   <editorActionHandler action="EditorBackSpace" implementationClass="com.intellij.codeInsight.lookup.impl.BackspaceHandler"/>