'J' shouldn't add whitespace if there is trailing whitespace

src/com/maddyhome/idea/vim/group/ChangeGroup.java

@@ -788,6 +788,9 @@ public class ChangeGroup {
     MotionGroup.moveCaret(editor, VimPlugin.getMotion().moveCaretToLineEnd(editor, startLine, true));
     for (int i = 1; i < count; i++) {
       int start = VimPlugin.getMotion().moveCaretToLineEnd(editor);
+      int trailingWhitespaceStart = VimPlugin.getMotion().moveCaretToLineEndSkipLeading(editor);
+      boolean hasTrailingWhitespace = start != trailingWhitespaceStart + 1;
+
       MotionGroup.moveCaret(editor, start);
       int offset;
       if (spaces) {
@@ -797,7 +800,7 @@ public class ChangeGroup {
         offset = VimPlugin.getMotion().moveCaretToLineStartOffset(editor);
       }
       deleteText(editor, new TextRange(editor.getCaretModel().getOffset(), offset), null);
-      if (spaces) {
+      if (spaces && !hasTrailingWhitespace) {
         insertText(editor, start, " ");
         MotionGroup.moveCaret(editor, VimPlugin.getMotion().moveCaretHorizontal(editor, -1, false));
       }

src/com/maddyhome/idea/vim/group/MotionGroup.java

@@ -1036,6 +1036,11 @@ public class MotionGroup {
     return EditorHelper.getLeadingCharacterOffset(editor, line);
   }
 
+  public int moveCaretToLineEndSkipLeading(@NotNull Editor editor) {
+    int logicalLine = editor.getCaretModel().getLogicalPosition().line;
+    return moveCaretToLineEndSkipLeading(editor, logicalLine);
+  }
+
   public int moveCaretToLineEndSkipLeading(@NotNull Editor editor, int line) {
     int start = EditorHelper.getLineStartOffset(editor, line);
     int end = EditorHelper.getLineEndOffset(editor, line, true);

test/org/jetbrains/plugins/ideavim/action/ChangeActionTest.java

@@ -273,6 +273,61 @@ public class ChangeActionTest extends VimTestCase {
            "quux\n");
   }
 
+  public void testDeleteJoinLinesSpaces() {
+    doTest(parseKeys("3J"),
+           "    a<caret> 1\n" +
+           "    b 2\n" +
+           "    c 3\n" +
+           "quux\n",
+           "    a 1 b 2 c 3\n" +
+           "quux\n");
+  }
+
+  public void testDeleteJoinLines() {
+    doTest(parseKeys("3gJ"),
+           "    a<caret> 1\n" +
+           "    b 2\n" +
+           "    c 3\n" +
+           "quux\n",
+           "    a 1    b 2    c 3\n" +
+           "quux\n");
+  }
+
+  public void testDeleteJoinLinesWithTrailingSpaceThenEmptyLine() {
+    doTest(parseKeys("3J"),
+           "foo \n" +
+           "\n" +
+           "bar",
+           "foo bar");
+  }
+
+  public void testDeleteJoinLinesWithTwoTrailingSpaces() {
+    doTest(parseKeys("J"),
+           "foo  \n" +
+           "bar",
+           "foo  bar");
+  }
+
+  public void testDeleteJoinVisualLinesSpaces() {
+    doTest(parseKeys("v2jJ"),
+           "    a<caret> 1\n" +
+           "    b 2\n" +
+           "    c 3\n" +
+           "quux\n",
+           "    a 1 b 2 c 3\n" +
+           "quux\n");
+  }
+
+  public void testDeleteJoinVisualLines() {
+    doTest(parseKeys("v2jgJ"),
+           "    a<caret> 1\n" +
+           "    b 2\n" +
+           "    c 3\n" +
+           "quux\n",
+           "    a 1    b 2    c 3\n" +
+           "quux\n");
+  }
+
   // VIM-511 |.|
   public void testRepeatWithBackspaces() {
     doTest(parseKeys("ce", "foo", "<BS><BS><BS>", "foo", "<Esc>", "j0", "."),