ClangFormat: Sprinkle some more magic pixie dust

Apparently, we can prevent clang-format from removing line breaks by
adding an empty comment at the end of the line.

Change-Id: Ia78ecb9e7351d059c544cbda11d33af5734e2218
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/clangformat/clangformatbaseindenter.cpp

@@ -250,6 +250,9 @@ int forceIndentWithExtraText(QByteArray &buffer,
                              const QTextBlock &block,
                              bool secondTry)
 {
+    if (!block.isValid())
+        return 0;
+
     const QString blockText = block.text();
     int firstNonWhitespace = Utils::indexOf(blockText,
                                             [](const QChar &ch) { return !ch.isSpace(); });
@@ -287,7 +290,16 @@ int forceIndentWithExtraText(QByteArray &buffer,
         dummyText = dummyTextForContext(charContext, closingBraceBlock);
     }
 
-    buffer.insert(utf8Offset, dummyText);
+    // A comment at the end of the line appears to prevent clang-format from removing line breaks.
+    if (dummyText == "/**/" || dummyText.isEmpty()) {
+        if (block.previous().isValid()) {
+            const int prevEndOffset = Utils::Text::utf8NthLineOffset(block.document(), buffer,
+                    block.blockNumber()) + block.previous().text().length();
+            buffer.insert(prevEndOffset, "//");
+            extraLength += 2;
+        }
+    }
+    buffer.insert(utf8Offset + extraLength, dummyText);
     extraLength += dummyText.length();
 
     if (secondTry) {

tests/unit/unittest/clangformat-test.cpp

@@ -198,14 +198,7 @@ TEST_F(ClangFormat, IndentLambdaWithReturnType)
                             "}"));
 }
 
-#ifndef KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
+TEST_F(ClangFormat, ClangFormatIndentFunctionArgumentLambdaWithNextLineScope)
-#  define DISABLED_FOR_VANILLA_CLANG(x) DISABLED_##x
-#else
-#  define DISABLED_FOR_VANILLA_CLANG(x) x
-#endif
-
-// This test requires the custom clang patch https://code.qt.io/cgit/clang/llvm-project.git/commit/?h=release_100-based&id=9b992a0f7f160dd6c75f20a4dcfcf7c60a4894df
-TEST_F(ClangFormat, DISABLED_FOR_VANILLA_CLANG(IndentFunctionArgumentLambdaWithNextLineScope))
 {
     insertLines({"foo([]()",
                  "{",
@@ -954,6 +947,16 @@ TEST_F(ClangFormat, SortIncludes)
                                              "#include <aa.h>",
                                              "#include <bb.h>"));
 }
+
+TEST_F(ClangFormat, ChainedMemberFunctionCalls)
+{
+    insertLines({"S().func().func()",
+                 ".func();"});
+    indenter.indent(cursor, QChar::Null, TextEditor::TabSettings());
+    ASSERT_THAT(documentLines(), ElementsAre("S().func().func()",
+                                             "    .func();"));
+}
+
 // clang-format on
 
 } // namespace