gn: beginnings of format command

tools/gn/tokenizer.cc

Index: tools/gn/tokenizer.cc
diff --git a/tools/gn/tokenizer.cc b/tools/gn/tokenizer.cc
index 87a4d909f35343c4b3f79fa0cc3cd42b636554eb..da7097cbf8f101b77e675f8caeaece6f5ed0acd7 100644
--- a/tools/gn/tokenizer.cc
+++ b/tools/gn/tokenizer.cc
@@ -5,6 +5,7 @@
 #include "tools/gn/tokenizer.h"
 
 #include "base/logging.h"
+#include "base/strings/string_util.h"
 #include "tools/gn/input_file.h"
 
 namespace {
@@ -107,9 +108,9 @@ std::vector<Token> Tokenizer::Run() {
     base::StringPiece token_value(&input_.data()[token_begin],
                                   token_end - token_begin);
 
-    if (type == Token::UNCLASSIFIED_OPERATOR)
+    if (type == Token::UNCLASSIFIED_OPERATOR) {
       type = GetSpecificOperatorType(token_value);
-    if (type == Token::IDENTIFIER) {
+    } else if (type == Token::IDENTIFIER) {
       if (token_value == "if")
         type = Token::IF;
       else if (token_value == "else")
@@ -118,14 +119,22 @@ std::vector<Token> Tokenizer::Run() {
         type = Token::TRUE_TOKEN;
       else if (token_value == "false")
         type = Token::FALSE_TOKEN;
+    } else if (type == Token::UNCLASSIFIED_COMMENT) {
+      // Find back to the previous \n, and trim. If it's only whitespace, then
+      // this is on a line alone, otherwise it's a suffix comment.
+      size_t newline_location = input_.find_last_of('\n', token_begin);
+      base::StringPiece to_newline = input_.substr(
+          newline_location + 1, token_begin - (newline_location + 1));
+      std::string trimmed;
+      // TODO(scottmg): Should write TrimString for StringPiece.
+      base::TrimWhitespace(to_newline.as_string(), base::TRIM_ALL, &trimmed);
+      if (trimmed.empty())
+        type = Token::LINE_COMMENT;
+      else
+        type = Token::SUFFIX_COMMENT;
     }
 
-    // TODO(brettw) This just strips comments from the token stream. This
-    // is probably wrong, they should be removed at a later stage so we can
-    // do things like rewrite the file. But this makes the parser simpler and
-    // is OK for now.
-    if (type != Token::COMMENT)
-      tokens_.push_back(Token(location, type, token_value));
+    tokens_.push_back(Token(location, type, token_value));
   }
   if (err_->has_error())
     tokens_.clear();
@@ -199,7 +208,7 @@ Token::Type Tokenizer::ClassifyCurrent() const {
     return Token::COMMA;
 
   if (next_char == '#')
-    return Token::COMMENT;
+    return Token::UNCLASSIFIED_COMMENT;
 
   // For the case of '-' differentiate between a negative number and anything
   // else.
@@ -285,7 +294,7 @@ void Tokenizer::AdvanceToEndOfToken(const Location& location,
       Advance();  // All are one char.
       break;
 
-    case Token::COMMENT:
+    case Token::UNCLASSIFIED_COMMENT:
       // Eat to EOL.
       while (!at_end() && !IsCurrentNewline())
         Advance();
@@ -339,7 +348,7 @@ void Tokenizer::Advance() {
 }
 
 Location Tokenizer::GetCurrentLocation() const {
-  return Location(input_file_, line_number_, char_in_line_);
+  return Location(input_file_, line_number_, char_in_line_, cur_);
 }
 
 Err Tokenizer::GetErrorForInvalidToken(const Location& location) const {