[clang-format] Fix tabs when using BreakBeforeTernaryOperators=false.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/52724.

This is rather a workaround than a correct fix. To properly fix it, we'd need to find a better way to tell when not to decrease the StartOfTokenColumn.

[MyDeveloperDay]

So am I right in thinking the <tab> got replaced out because C.Spaces was > C.StartOfTokenColumn? (i.e. appendIndentText was given a negative number as the 4th argument)

[curdeius]

In D115803#3195115, @MyDeveloperDay wrote:

So am I right in thinking the <tab> got replaced out because C.Spaces was > C.StartOfTokenColumn? (i.e. appendIndentText was given a negative number as the 4th argument)

Yes, that's it. It's not actually negative because that's an unsigned value, so it underflows and gets big. That's also a reason why we can't just check for a non-positive value instead of a zero i. appendIndentText (that would be a different workaround though).

clang/lib/Format/WhitespaceManager.cpp

for (unsigned i = 0, e = Changes.size(); i != e; ++i) {
     if (C.CreateReplacement) {
       std::string ReplacementText = C.PreviousLinePostfix;
       if (C.ContinuesPPDirective)
         appendEscapedNewlineText(ReplacementText, C.NewlinesBefore,
                                  C.PreviousEndOfTokenColumn,
                                  C.EscapedNewlineColumn);
       else
         appendNewlineText(ReplacementText, C.NewlinesBefore);
+      // FIXME: This assert should hold if we computed the column correctly.
+      // assert((int)C.StartOfTokenColumn >= C.Spaces);
       appendIndentText(
           ReplacementText, C.Tok->IndentLevel, std::max(0, C.Spaces),
-          C.StartOfTokenColumn - std::max(0, C.Spaces), C.IsAligned);
+          std::max((int)C.StartOfTokenColumn, C.Spaces) - std::max(0, C.Spaces),
+          C.IsAligned);
       ReplacementText.append(C.CurrentLinePrefix);
       storeReplacement(C.OriginalWhitespaceRange, ReplacementText);
     }
   }
 }
 
 void WhitespaceManager::storeReplacement(SourceRange Range, StringRef Text) {
   unsigned WhitespaceLength = SourceMgr.getFileOffset(Range.getEnd()) -

clang/unittests/Format/FormatTest.cpp

EXPECT_EQ("{\n"
             "}",
             format("{\n"
                    "\t/*\n"
                    " asdf\n"
                    "\t*/\n"
                    "}",
                    Tab));
 
+  verifyFormat("void f() {\n"
+               "\treturn true ? aaaaaaaaaaaaaaaaaa\n"
+               "\t            : bbbbbbbbbbbbbbbbbb\n"
+               "}",
+               Tab);
+  FormatStyle TabNoBreak = Tab;
+  TabNoBreak.BreakBeforeTernaryOperators = false;
+  verifyFormat("void f() {\n"
+               "\treturn true ? aaaaaaaaaaaaaaaaaa :\n"
+               "\t              bbbbbbbbbbbbbbbbbb\n"
+               "}",
+               TabNoBreak);
+  verifyFormat("void f() {\n"
+               "\treturn true ?\n"
+               "\t           aaaaaaaaaaaaaaaaaaaa :\n"
+               "\t           bbbbbbbbbbbbbbbbbbbb\n"
+               "}",
+               TabNoBreak);
+
   Tab.UseTab = FormatStyle::UT_Never;
   EXPECT_EQ("/*\n"
             "              a\t\tcomment\n"
             "              in multiple lines\n"
             "       */",
             format("   /*\t \t \n"
                    " \t \t a\t\tcomment\t \t\n"
                    " \t \t in multiple lines\t\n"