IDEA-18764 Emacs-Mode: Ctrl-y only pastes the last line killed and not the entire kill buffer

1. The action removes line feed if [caret offset; line end) interval doesn't contain non-white space symbols;
2. Refactoring: common functionality is moved to utility class;
3, Test are added;

platform/platform-impl/src/com/intellij/openapi/editor/actions/CutLineEndAction.java

@@ -24,14 +24,13 @@
  */
 package com.intellij.openapi.editor.actions;
 
-import com.intellij.openapi.ide.KillRingTransferable;
 import com.intellij.openapi.actionSystem.DataContext;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.editor.actionSystem.EditorAction;
 import com.intellij.openapi.editor.actionSystem.EditorWriteActionHandler;
-import com.intellij.openapi.ide.CopyPasteManager;
-import com.intellij.openapi.util.text.StringUtil;
+import com.intellij.util.text.CharArrayUtil;
+import org.jetbrains.annotations.NotNull;
 
 public class CutLineEndAction extends EditorAction {
   public CutLineEndAction() {
@@ -47,37 +46,35 @@ public class CutLineEndAction extends EditorAction {
 
     public void executeWriteAction(Editor editor, DataContext dataContext) {
       final Document doc = editor.getDocument();
-      if (doc.getLineCount() == 0) return;
       int caretOffset = editor.getCaretModel().getOffset();
+      if (caretOffset >= doc.getTextLength()) {
+        return;
+      }
       final int lineNumber = doc.getLineNumber(caretOffset);
       int lineEndOffset = doc.getLineEndOffset(lineNumber);
 
+      int start;
+      int end;
       if (caretOffset >= lineEndOffset) {
-        if (myCopyToClipboard) {
-          copyToClipboard(doc, lineEndOffset, lineEndOffset + 1);
-        }
-        doc.deleteString(lineEndOffset, lineEndOffset + 1);
-        return;
-      }
-
-      if (myCopyToClipboard) {
-        copyToClipboard(doc, caretOffset, lineEndOffset);
-      }
-
-      final int lineStartOffset = doc.getLineStartOffset(lineNumber);
-      if (StringUtil.isEmptyOrSpaces(doc.getCharsSequence().subSequence(lineStartOffset, lineEndOffset).toString())) {
-        DeleteLineAction.deleteLineAtCaret(editor);
+        start = lineEndOffset;
+        end = lineEndOffset + 1;
       }
       else {
-        doc.deleteString(caretOffset, lineEndOffset);
+        start = caretOffset;
+        end = lineEndOffset;
+        if (lineEndOffset < doc.getTextLength() && CharArrayUtil.isEmptyOrSpaces(doc.getCharsSequence(), caretOffset, lineEndOffset)) {
+          end++;
+        }
       }
+
+      delete(doc, start, end);
     }
 
-    private static void copyToClipboard(final Document doc, int startOffset, int endOffset) {
-      String s = doc.getCharsSequence().subSequence(startOffset, endOffset).toString();
-
-      s = StringUtil.convertLineSeparators(s);
-      CopyPasteManager.getInstance().setContents(new KillRingTransferable(s, doc, startOffset, startOffset, true));
+    private void delete(@NotNull Document document, int start, int end) {
+      if (myCopyToClipboard) {
+        EditorActionUtil.copyToKillRing(document, start, end, true);
+      }
+      document.deleteString(start, end);
     }
   }
 }

platform/platform-impl/src/com/intellij/openapi/editor/actions/EditorActionUtil.java

@@ -34,10 +34,13 @@ import com.intellij.openapi.editor.event.EditorMouseEvent;
 import com.intellij.openapi.editor.event.EditorMouseEventArea;
 import com.intellij.openapi.editor.ex.EditorEx;
 import com.intellij.openapi.editor.ex.util.EditorUtil;
+import com.intellij.openapi.ide.CopyPasteManager;
+import com.intellij.openapi.ide.KillRingTransferable;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.Key;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.util.EditorPopupHandler;
+import org.jetbrains.annotations.NotNull;
 
 import java.awt.*;
 import java.awt.event.MouseEvent;
@@ -645,6 +648,21 @@ public class EditorActionUtil {
     setupSelection(editor, isWithSelection, selectionStart, blockSelectionStart);
   }
 
+  /**
+   * Copies target region from the given offset to the kill ring, i.e. combines it with the previously
+   * copied/cut adjacent text if necessary and puts to the clipboard. 
+   * 
+   * @param document        target document
+   * @param startOffset     start offset of the target region within the given document
+   * @param endOffset       end offset of the target region within the given document
+   * @param cut             flag that identifies if target text region will be cut from the given document
+   */
+  public static void copyToKillRing(@NotNull final Document document, int startOffset, int endOffset, boolean cut) {
+    String s = document.getCharsSequence().subSequence(startOffset, endOffset).toString();
+    s = StringUtil.convertLineSeparators(s);
+    CopyPasteManager.getInstance().setContents(new KillRingTransferable(s, document, startOffset, endOffset, cut));
+  }
+  
   public static EditorPopupHandler createEditorPopupHandler(final String groupId) {
     return new EditorPopupHandler() {
       public void invokePopup(final EditorMouseEvent event) {

platform/platform-impl/testSrc/com/intellij/openapi/editor/actions/CutLineEndActionsTest.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2000-2011 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.openapi.editor.actions;
+
+import com.intellij.testFramework.LightPlatformCodeInsightTestCase;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.IOException;
+
+/**
+ * @author Denis Zhdanov
+ * @since 4/18/11 2:47 PM
+ */
+public class CutLineEndActionsTest extends LightPlatformCodeInsightTestCase {
+  
+  public void testNonEmptyLineEnd() throws IOException {
+    doTest(
+      "class Test {\n" +
+      "    // This is a <caret>comment string\n" +
+      "}",
+      "class Test {\n" +
+      "    // This is a <caret>\n" +
+      "}"
+    );
+  }
+
+  public void testEmptyLineEnd() throws IOException {
+    doTest(
+      "class Test {\n" +
+      "    <caret>   \n" +
+      "    // some comment\n" +
+      "}",
+      "class Test {\n" +
+      "    <caret>    // some comment\n" +
+      "}"
+    );
+  }
+  
+  public void testAtLineEnd() throws IOException {
+    doTest(
+      "class Test {\n" +
+      "    // This is a comment string1<caret>\n" +
+      "    // This is a comment string2\n" +
+      "}",
+      "class Test {\n" +
+      "    // This is a comment string1<caret>    // This is a comment string2\n" +
+      "}"
+    );
+  }
+  
+  public void testAtDocumentEnd() throws IOException {
+    String text = 
+      "class Test{\n" +
+      "}<caret>";
+    doTest(text, text);
+  }
+  
+  public void testEmptyLastLineEnd() throws IOException {
+    doTest(
+      "class Test {\n" +
+      "}<caret>         ",
+      "class Test {\n" +
+      "}<caret>"
+    );
+  }
+  
+  private void doTest(@NotNull String before, @NotNull String after) throws IOException {
+    configureFromFileText(getTestName(false) + ".java", before);
+    cutToLineEnd();
+    checkResultByText(after);
+  }
+}

platform/testFramework/src/com/intellij/testFramework/LightPlatformCodeInsightTestCase.java

@@ -500,6 +500,10 @@ public abstract class LightPlatformCodeInsightTestCase extends LightPlatformTest
     doAction("EditorNextWordWithSelection");
   }
   
+  protected static void cutToLineEnd() {
+    doAction("EditorCutLineEnd");
+  }
+  
   protected static void lineComment() {
     new CommentByLineCommentHandler().invoke(getProject(), getEditor(), getFile());
   }

platform/util/src/com/intellij/util/text/CharArrayUtil.java

@@ -16,6 +16,7 @@
 package com.intellij.util.text;
 
 import com.intellij.openapi.util.TextRange;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.ByteArrayOutputStream;
@@ -523,4 +524,22 @@ public class CharArrayUtil {
     }
     return false;
   }
+
+  /**
+   * Allows to answer if target region of the given text contains only white space symbols (tabulations, white spaces and line feeds).
+   * 
+   * @param text      text to check
+   * @param start     start offset within the given text to check (inclusive)
+   * @param end       end offset within the given text to check (exclusive)
+   * @return          <code>true</code> if target region of the given text contains white space symbols only; <code>false</code> otherwise
+   */
+  public static boolean isEmptyOrSpaces(@NotNull CharSequence text, int start, int end) {
+    for (int i = start; i < end; i++) {
+      char c = text.charAt(i);
+      if (c != ' ' && c != '\t' && c != '\n') {
+        return false;
+      }
+    }
+    return true;
+  }
 }