[clang-format] Fix aligning of trailing comments after comment at the end of a namespace

[eoanermine]

Summary

• Fix aligning of trailing comments after comment at the end of a namespace
• Add tests for aligning of trailing comments after comment that documents the closing of a namespace

Closes https://github.com/llvm/llvm-project/issues/26550

[HazardyKnusperkeks]

clang/unittests/Format/FormatTest.cpp

17468–17470

Shouldn't this be aligned?

17479

Why repeat this here with just a longer comment, or do I miss something?

clang/lib/Format/WhitespaceManager.cpp

if (Changes[i].NewlinesBefore == 1) { // A comment on its own line.
       unsigned CommentColumn = SourceMgr.getSpellingColumnNumber(
           Changes[i].OriginalWhitespaceRange.getEnd());
       for (unsigned j = i + 1; j != e; ++j) {
         if (Changes[j].Tok->is(tok::comment))
           continue;
 
         unsigned NextColumn = SourceMgr.getSpellingColumnNumber(
             Changes[j].OriginalWhitespaceRange.getEnd());
+        // Handle files without newline before the end of file correct
+        if (Changes[j].Tok->is(tok::eof))
+          NextColumn = 1;
+
         // The start of the next token was previously aligned with the
         // start of this comment.
         WasAlignedWithStartOfNextLine =
             CommentColumn == NextColumn ||
             CommentColumn == NextColumn + Style.IndentWidth;
         break;
       }
     }

clang/unittests/Format/FormatTest.cpp

verifyFormat("int a_long_name = 1;\n"
                Alignment);
   verifyFormat("int a_long_name = 1;\n"
                "auto b          = B{{a_long_name, a_long_name},\n"
                "                    {a_longer_name_for_wrap,\n"
                "                     a_longer_name_for_wrap}};",
                Alignment);
 }
 
+TEST_F(FormatTest, AlignTrailingComments) {
+  FormatStyle Style = getLLVMStyle();
+  EXPECT_EQ(Style.AlignTrailingComments, true);
+
+  verifyFormat("namespace test {\n"
+               "class C;\n"
+               "} // namespace test\n"
+               "// Lorem ipsum dolor sit amet, consectetur adipiscing elit. "
+               "Nullam cursus nunc\n"
+               "// non",
+               Style);
+  verifyFormat("namespace test {\n"
+               "class C;\n"
+               "} // namespace test\n"
+               "// Lorem ipsum dolor sit amet, consectetur adipiscing elit. "
+               "Nullam cursus nunc\n"
+               "// non\n",
+               Style);
+  verifyFormat("namespace test {\n"
+               "class C;\n"
+               "} // namespace test\n"
+               "// Lorem ipsum dolor sit amet, consectetur adipiscing elit. "
+               "Nullam cursus nunc\n"
+               "// non other text",
+               Style);
+  verifyFormat("namespace test {\n"
+               "class C;\n"
+               "} // namespace test\n"
+               "// Lorem ipsum dolor sit amet, consectetur adipiscing elit. "
+               "Nullam cursus nunc\n"
+               "// non other text\n",
+               Style);
+}
+
 TEST_F(FormatTest, AlignConsecutiveBitFields) {
   FormatStyle Alignment = getLLVMStyle();
   Alignment.AlignConsecutiveBitFields.Enabled = true;
   verifyFormat("int const a     : 5;\n"
                "int oneTwoThree : 23;",
                Alignment);
 
   // Initializers are allowed starting with c++2a