[clang-format] Improve understanding of combined typedef+record declarations

[jtbandes]

Summary

Fixes an issue where struct A { int X; }; would be broken onto multiple lines, but typedef struct A { int X; } A2; was collapsed onto a single line.

[jtbandes]

It strikes me that this doesn't handle using-style type aliases, but it seems hard to do this correctly in general, so still valuable to catch this simple, common case. Let me know if you have any better suggestions!

[jtbandes]

Ping :)

[djasper]

One nit, otherwise looks good.

lib/Format/UnwrappedLineFormatter.cpp

367–368

Don't use "T", that's too much engrained as template parameter. Use "Tok".

[jtbandes]

Update from review

[jtbandes]

lib/Format/UnwrappedLineFormatter.cpp

367–368

Added nested scope to avoid shadowing Tok from above.

[jtbandes]

Another ping.

[djasper]

Renamed Tok to RecordTok to avoid the nested scope and submitted as r305667.

lib/Format/UnwrappedLineFormatter.cpp

if (Tok->is(tok::r_brace) && !Tok->MustBreakBefore &&
         (Tok->getNextNonComment() == nullptr ||
          Tok->getNextNonComment()->is(tok::semi))) {
       // We merge empty blocks even if the line exceeds the column limit.
       Tok->SpacesRequiredBefore = 0;
       Tok->CanBreakBefore = true;
       return 1;
     } else if (Limit != 0 && !Line.startsWith(tok::kw_namespace) &&
                !startsExternCBlock(Line)) {
       // We don't merge short records.
-      if (Line.First->isOneOf(tok::kw_class, tok::kw_union, tok::kw_struct,
-                              Keywords.kw_interface))
+      {
+        FormatToken *Tok =
+            Line.First->is(tok::kw_typedef) ? Line.First->Next : Line.First;
+        if (Tok &&
+            Tok->isOneOf(tok::kw_class, tok::kw_union, tok::kw_struct,
           return 0;
+      }
 
       // Check that we still have three lines and they fit into the limit.
       if (I + 2 == E || I[2]->Type == LT_Invalid)
         return 0;
       Limit = limitConsideringMacros(I + 2, E, Limit);
 
       if (!nextTwoLinesFitInto(I, Limit))
         return 0;

unittests/Format/FormatTest.cpp

verifyFormat("if (true) {\n"
                AllowSimpleBracedStatements);
   verifyFormat("if (true) {\n"
                "  f();\n"
                "} else {\n"
                "  f();\n"
                "}",
                AllowSimpleBracedStatements);
 
+  verifyFormat("struct A2 {\n"
+               "  int X;\n"
+               "};",
+               AllowSimpleBracedStatements);
+  verifyFormat("typedef struct A2 {\n"
+               "  int X;\n"
+               "} A2_t;",
+               AllowSimpleBracedStatements);
   verifyFormat("template <int> struct A2 {\n"
                "  struct B {};\n"
                "};",
                AllowSimpleBracedStatements);
 
   AllowSimpleBracedStatements.AllowShortIfStatementsOnASingleLine = false;
   verifyFormat("if (true) {\n"
                "  f();\n"