[clang-format] Fix reflow in block comment lines with leading whitespace.

[krasimir]

Summary

The reflower was not taking into account the additional leading whitespace in block comment lines.

source:

{
/*
 * long long long long
 *   long
 * long long long long
 */
}

format (with column limit 20) before:

{
  /*
   * long long long
   * long long long long
   * long long
   */
}

format after:

{
  /*
   * long long long
   * long long long
   * long long long
   */
}

[djasper]

I don't know. I could also make an argument that more than one space at the beginning of a line should just stop the reflow. E.g. I could see people writing paragraphs like this:

/*
 * This is my long text. This is
 * paragraph one.
 *   If I add two or three spaces,
 * here, it's probably easy to see
 * that this is separate.
 */

That said, I am fine submitting this for now.

[krasimir]

@djasper: I agree with the two spaces rule. Sounds pretty reasonable. Will add this feature eventually.

cfe/trunk/lib/Format/BreakableToken.cpp

unsigned BreakableBlockComment::getReflownColumn(
     return ReflownColumn;
 }
 
 unsigned BreakableBlockComment::getLineLengthAfterSplitBefore(
     unsigned LineIndex, unsigned TailOffset,
     unsigned PreviousEndColumn,
     unsigned ColumnLimit,
     Split SplitBefore) const {
-    if (SplitBefore.first == StringRef::npos ||
-        SplitBefore.first + SplitBefore.second < Content[LineIndex].size()) {
-      // A piece of line, not the whole, gets reflown.
-      return getLineLengthAfterSplit(LineIndex, TailOffset, StringRef::npos);
+      // Block comment line contents contain the trailing whitespace after the
+      // decoration, so the need of left trim. Note that this behavior is
+      // consistent with the breaking of block comments where the indentation of
+      // a broken line is uniform across all the lines of the block comment.
+      SplitBefore.first + SplitBefore.second <
+          Content[LineIndex].ltrim().size()) {
   } else {
     // The whole line gets reflown, need to check if we need to insert a break
     // for the postfix or not.
     StringRef TrimmedContent = Content[LineIndex].ltrim(Blanks);
     unsigned ReflownColumn =
         getReflownColumn(TrimmedContent, LineIndex, PreviousEndColumn);
     if (ReflownColumn <= ColumnLimit) {
       return ReflownColumn;

cfe/trunk/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, ReflowsComments) {
   EXPECT_EQ("/* long long long\n"
             " * long long longg\n"
             " */",
             format("/* long long long long\n"
                    " * long\n"
                    " * longg */",
                    getLLVMStyleWithColumns(20)));
 
+  // Reflow lines with leading whitespace.
+  EXPECT_EQ("{\n"
+            "  /*\n"
+            "   * long long long\n"
+            "   * long long long\n"
+            "   * long long long\n"
+            "   */\n"
+            "}",
+            format("{\n"
+                   "/*\n"
+                   " * long long long long\n"
+                   " *   long\n"
+                   " * long long long long\n"
+                   " */\n"
+                   "}",
+                   getLLVMStyleWithColumns(20)));
+
   // Break single line block comments that are first in the line with ' *'
   // decoration.
   EXPECT_EQ("/* long long long\n"
             " * long */",
             format("/* long long long long */", getLLVMStyleWithColumns(20)));
 
   // Break single line block comment that are not first in the line with '  '
   // decoration.