[clang-format] Do not merge short C# class definitions into one line

[jbcoe]

Summary

Skip access specifiers before record definitions when deciding whether or not to wrap lines so that C# class definitions do not get wrapped into a single line.

[krasimir]

Thanks! Looks like this is OK also for Java, I'm not sure about ObjC. If it happens to affect other languages negatively, we can restrict by adding language-specific checks.

clang/lib/Format/UnwrappedLineFormatter.cpp

if (Line.Last->is(tok::l_brace)) {
         Tok->CanBreakBefore = true;
         return 1;
       } else if (Limit != 0 && !Line.startsWithNamespace() &&
                  !startsExternCBlock(Line)) {
         // We don't merge short records.
         FormatToken *RecordTok = Line.First;
         // Skip record modifiers.
         while (RecordTok->Next &&
-               RecordTok->isOneOf(tok::kw_typedef, tok::kw_export,
-                                  Keywords.kw_declare, Keywords.kw_abstract,
-                                  tok::kw_default))
+               RecordTok->isOneOf(
+                   tok::kw_typedef, tok::kw_export, Keywords.kw_declare,
+                   Keywords.kw_abstract, tok::kw_default, tok::kw_public,
+                   tok::kw_private, tok::kw_protected, Keywords.kw_internal))
           RecordTok = RecordTok->Next;
         if (RecordTok &&
             RecordTok->isOneOf(tok::kw_class, tok::kw_union, tok::kw_struct,
                                Keywords.kw_interface))
           return 0;
 
         // Check that we still have three lines and they fit into the limit.
         if (I + 2 == E || I[2]->Type == LT_Invalid)

clang/unittests/Format/FormatTestCSharp.cpp

verifyFormat("public class SomeClass\n"
                "        while (true)\n"
                "            f();\n"
                "        for (;;)\n"
                "            f();\n"
                "        if (true)\n"
                "            f();\n"
                "    }\n"
                "}");
+
+  // Ensure that small and empty classes are handled correctly with condensed
+  // (Google C++-like) brace-breaking style.
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
+  Style.BreakBeforeBraces = FormatStyle::BS_Attach;
+
+  verifyFormat("public class SomeEmptyClass {}", Style);
+
+  verifyFormat("public class SomeTinyClass {\n"
+               "  int X;\n"
+               "}",
+               Style);
+  verifyFormat("private class SomeTinyClass {\n"
+               "  int X;\n"
+               "}",
+               Style);
+  verifyFormat("protected class SomeTinyClass {\n"
+               "  int X;\n"
+               "}",
+               Style);
+  verifyFormat("internal class SomeTinyClass {\n"
+               "  int X;\n"
+               "}",
+               Style);
 }
 
 TEST_F(FormatTestCSharp, AccessModifiers) {
   verifyFormat("public String toString()\n"
                "{\n"
                "}");
   verifyFormat("private String toString()\n"
                "{\n"