[clang-format] Re-align broken comment lines where appropriate.

[krasimir]

Summary

The comment aligner was skipping over newly broken comment lines. This patch fixes that.

source:

int ab; // line
int a; // long long

format with column limit 15 before:

int ab; // line
int a;  // long
       // long

format with column limit 15 after:

int ab; // line
int a;  // long
        // long

[krasimir]

• Add a few more tests.

[djasper]

Thanks and sorry if I caused this :(

[krasimir]

It's very unlikely that you caused this. After re-flowing lots of cases started going over alternative code paths, and this looks like an instance of that.

lib/Format/WhitespaceManager.cpp

void WhitespaceManager::calculateLineBreakInformation() {
   // FIXME: The last token is currently not always an eof token; in those
   // cases, setting TokenLength of the last token to 0 is wrong.
   Changes.back().TokenLength = 0;
   Changes.back().IsTrailingComment = Changes.back().Tok->is(tok::comment);
 
   const WhitespaceManager::Change *LastBlockComment = nullptr;
   for (auto &Change : Changes) {
     // Reset the IsTrailingComment flag for changes inside of trailing comments
-    // so they don't get realigned later.
-    if (Change.IsInsideToken)
+    // so they don't get realigned later. Comment line breaks however still need
+    // to be aligned.
+    if (Change.IsInsideToken && Change.NewlinesBefore == 0)
       Change.IsTrailingComment = false;
     Change.StartOfBlockComment = nullptr;
     Change.IndentationOffset = 0;
     if (Change.Tok->is(tok::comment)) {
       if (Change.Tok->is(TT_LineComment) || !Change.IsInsideToken)
         LastBlockComment = &Change;
       else {
         if ((Change.StartOfBlockComment = LastBlockComment))

unittests/Format/FormatTest.cpp

EXPECT_EQ("int i = f(abc, // line 1\n"
             "          d,   // line 2\n"
             "               // line 3\n"
             "          b);",
             format("int i = f(abc, // line 1\n"
                    "          d, // line 2\n"
                    "             // line 3\n"
                    "          b);",
                    getLLVMStyleWithColumns(40)));
+
+  // Align newly broken trailing comments.
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n",
+            format("int ab; // line\n"
+                   "int a; // long long\n",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "        // long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "       // long",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "pt c;   // long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "pt c; // long",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "\n"
+            "// long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "\n"
+                   "// long",
+                   getLLVMStyleWithColumns(15)));
 }
 } // end namespace
 } // end namespace format
 } // end namespace clang