IDEA-167746 Carry completion list over to the next line on Shift+Enter

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

@@ -1840,4 +1840,16 @@ ita<caret>
     assert lookup
   }
 
+  void "test don't close lookup when starting a new line"() {
+    myFixture.configureByText 'a.java', 'class Foo {{ "abc"<caret> }}'
+    type '.'
+    assert lookup
+    edt {
+      myFixture.performEditorAction(IdeActions.ACTION_EDITOR_START_NEW_LINE)
+      assert lookup
+      assert lookup.lookupStart == myFixture.editor.caretModel.offset
+      assert myFixture.editor.document.text.contains('\n')
+    }
+  }
+
 }

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

@@ -376,6 +376,11 @@ public class LookupImpl extends LightweightHint implements LookupEx, Disposable
     return true;
   }
 
+  void moveToCaretPosition() {
+    myOffsets.destabilizeLookupStart();
+    refreshUi(false, true);
+  }
+
   private boolean updateList(boolean onExplicitAction, boolean reused) {
     if (!ApplicationManager.getApplication().isUnitTestMode()) {
       ApplicationManager.getApplication().assertIsDispatchThread();

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

@@ -86,6 +86,10 @@ public class LookupOffsets implements DocumentListener {
     return true;
   }
 
+  void destabilizeLookupStart() {
+    myStableStart = false;
+  }
+
   void checkMinPrefixLengthChanges(Collection<LookupElement> items, LookupImpl lookup) {
     if (myStableStart) return;
     if (!lookup.isCalculating() && !items.isEmpty()) {

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

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2000-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.codeInsight.lookup.impl;
+
+import com.intellij.codeInsight.lookup.LookupManager;
+import com.intellij.openapi.actionSystem.DataContext;
+import com.intellij.openapi.editor.Caret;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.editor.actionSystem.EditorActionHandler;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * @author peter
+ */
+public class StartNewLineHandler extends EditorActionHandler {
+  private final EditorActionHandler myOriginalHandler;
+
+  public StartNewLineHandler(EditorActionHandler originalHandler) {
+    myOriginalHandler = originalHandler;
+  }
+
+  @Override
+  protected void doExecute(Editor editor, @Nullable Caret caret, DataContext dataContext) {
+    Runnable callOriginal = () -> {
+      if (myOriginalHandler != null) {
+        myOriginalHandler.execute(editor, caret, dataContext);
+      }
+    };
+    LookupImpl lookup = (LookupImpl)LookupManager.getActiveLookup(editor);
+    if (lookup != null && lookup.getLookupStart() == lookup.getLookupOriginalStart()) {
+      lookup.performGuardedChange(callOriginal);
+      lookup.moveToCaretPosition();
+    } else {
+      callOriginal.run();
+    }
+  }
+}

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

@@ -723,6 +723,7 @@
     <editorActionHandler action="EditorLeft" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$LeftHandler"/>
     <editorActionHandler action="EditorRight" implementationClass="com.intellij.codeInsight.lookup.impl.LookupActionHandler$RightHandler"/>
     <editorActionHandler action="EditorBackSpace" implementationClass="com.intellij.codeInsight.lookup.impl.BackspaceHandler" id="backspace.lookup"/>
+    <editorActionHandler action="EditorStartNewLine" implementationClass="com.intellij.codeInsight.lookup.impl.StartNewLineHandler" id="backspace.lookup"/>
 
     <!-- CodeInsightSettings -->
     <editorActionHandler action="EditorEnter" implementationClass="com.intellij.codeInsight.editorActions.EnterHandler" id="editorEnter"/>