[clang-format] Remove empty lines before }[;] // comment

[krasimir]

Summary

This addresses bug 36766 and a FIXME in tests about empty lines before
}[;] // comment lines.

lib/Format/UnwrappedLineFormatter.cpp

if (RootToken.is(tok::eof)) {
     Whitespaces->replaceWhitespace(RootToken, Newlines, TokenIndent,
                                    TokenIndent);
     return;
   }
   unsigned Newlines =
       std::min(RootToken.NewlinesBefore, Style.MaxEmptyLinesToKeep + 1);
   // Remove empty lines before "}" where applicable.
   if (RootToken.is(tok::r_brace) &&
+      // Look for "}", "} // comment", "};" or "}; // comment".
       (!RootToken.Next ||
-       (RootToken.Next->is(tok::semi) && !RootToken.Next->Next)))
+       (RootToken.Next->is(tok::comment) && !RootToken.Next->Next) ||
+       (RootToken.Next->is(tok::semi) &&
+        (!RootToken.Next->Next || (RootToken.Next->Next->is(tok::comment) &&
+                                   !RootToken.Next->Next->Next)))))
     Newlines = std::min(Newlines, 1u);
   // Remove empty lines at the start of nested blocks (lambdas/arrow functions)
   if (PreviousLine == nullptr && Line.Level > 0)
     Newlines = std::min(Newlines, 1u);
   if (Newlines == 0 && !RootToken.IsFirst)
     Newlines = 1;
   if (RootToken.IsFirst && !RootToken.HasUnescapedNewline)
     Newlines = 0;

unittests/Format/FormatTest.cpp

EXPECT_EQ("void f() {\n"
                    "\n"
                    "  } else if (b) {\n"
                    "    f();\n"
                    "\n"
                    "  }\n"
                    "\n"
                    "}"));
 
-  // FIXME: This is slightly inconsistent.
   FormatStyle LLVMWithNoNamespaceFix = getLLVMStyle();
   LLVMWithNoNamespaceFix.FixNamespaceComments = false;
   EXPECT_EQ("namespace {\n"
             "int i;\n"
             "}",
             format("namespace {\n"
                    "int i;\n"
                    "\n"
                    "}", LLVMWithNoNamespaceFix));
   EXPECT_EQ("namespace {\n"
             "int i;\n"
             "}",
             format("namespace {\n"
                    "int i;\n"
                    "\n"
                    "}"));
   EXPECT_EQ("namespace {\n"
             "int i;\n"
+            "};",
+            format("namespace {\n"
+                   "int i;\n"
                    "\n"
+                   "};"));
+  EXPECT_EQ("namespace {\n"
+            "int i;\n"
             "} // namespace",
             format("namespace {\n"
                    "int i;\n"
                    "\n"
                    "}  // namespace"));
+  EXPECT_EQ("namespace {\n"
+            "int i;\n"
+            "}; // namespace",
+            format("namespace {\n"
+                   "int i;\n"
+                   "\n"
+                   "};  // namespace"));
 
   FormatStyle Style = getLLVMStyle();
   Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
   Style.MaxEmptyLinesToKeep = 2;
   Style.BreakBeforeBraces = FormatStyle::BS_Custom;
   Style.BraceWrapping.AfterClass = true;
   Style.BraceWrapping.AfterFunction = true;
   Style.KeepEmptyLinesAtTheStartOfBlocks = false;