Remove some of the state handoff via ivars within Parser.

Hopefully makes things a litte easier to follow.

src/google/protobuf/compiler/objectivec/objectivec_helpers.cc

@@ -1638,70 +1638,69 @@ class Parser {
   Parser(LineConsumer* line_consumer)
       : line_consumer_(line_consumer), line_(0) {}
 
-  // Parses a check of input, returning success/failure.
-  bool ParseChunk(StringPiece chunk);
+  // Feeds in some input, prase what it can, returning success/failure. Calling
+  // again after an error is undefined.
+  bool ParseChunk(StringPiece chunk, std::string* out_error);
 
   // Should be called to finish parsing (after all input has been provided via
-  // ParseChunk()).  Returns success/failure.
-  bool Finish();
+  // successful calls to ParseChunk(), calling after a ParseChunk() failure is
+  // undefined). Returns success/failure.
+  bool Finish(std::string* out_error);
 
   int last_line() const { return line_; }
-  std::string error_str() const { return error_str_; }
 
  private:
-  bool ParseLoop();
-
   LineConsumer* line_consumer_;
   int line_;
-  std::string error_str_;
-  StringPiece p_;
   std::string leftover_;
 };
 
-bool Parser::ParseChunk(StringPiece chunk) {
+bool Parser::ParseChunk(StringPiece chunk, std::string* out_error) {
+  StringPiece full_chunk;
   if (!leftover_.empty()) {
     leftover_ += std::string(chunk);
-    p_ = StringPiece(leftover_);
+    full_chunk = StringPiece(leftover_);
   } else {
-    p_ = chunk;
+    full_chunk = chunk;
+  }
+
+  StringPiece line;
+  while (ReadLine(&full_chunk, &line)) {
+    ++line_;
+    RemoveComment(&line);
+    TrimWhitespace(&line);
+    if (!line.empty() && !line_consumer_->ConsumeLine(line, out_error)) {
+      if (out_error->empty()) {
+        *out_error = "ConsumeLine failed without setting an error.";
+      }
+      leftover_.clear();
+      return false;
+    }
   }
-  bool result = ParseLoop();
-  if (p_.empty()) {
+
+  if (full_chunk.empty()) {
     leftover_.clear();
   } else {
-    leftover_ = std::string(p_);
+    leftover_ = std::string(full_chunk);
   }
-  return result;
+  return true;
 }
 
-bool Parser::Finish() {
+bool Parser::Finish(std::string* out_error) {
   // If there is still something to go, flush it with a newline.
-  if (!leftover_.empty() && !ParseChunk("\n")) {
+  if (!leftover_.empty() && !ParseChunk("\n", out_error)) {
     return false;
   }
   // This really should never fail if ParseChunk succeeded, but check to be sure.
-  return leftover_.empty();
-}
-
-bool Parser::ParseLoop() {
-  StringPiece line;
-  while (ReadLine(&p_, &line)) {
-    ++line_;
-    RemoveComment(&line);
-    TrimWhitespace(&line);
-    if (line.empty()) {
-      continue;  // Blank line.
-    }
-    if (!line_consumer_->ConsumeLine(line, &error_str_)) {
-      return false;
-    }
+  if (!leftover_.empty()) {
+    *out_error = "ParseSimple Internal error: finished with pending data.";
+    return false;
   }
   return true;
 }
 
-std::string ParserErrorString(const Parser& parser, const std::string& name) {
-  return std::string("error: ") + name + " Line " +
-    StrCat(parser.last_line()) + ", " + parser.error_str();
+std::string FullErrorString(const std::string& name, int line_num, const std::string& msg) {
+  return std::string("error: ") + name + " Line " + StrCat(line_num) + ", " + msg;
 }
 
 }  // namespace
@@ -1731,6 +1730,7 @@ bool ParseSimpleStream(io::ZeroCopyInputStream& input_stream,
                        const std::string& stream_name,
                        LineConsumer* line_consumer,
                        std::string* out_error) {
+  std::string local_error;
   Parser parser(line_consumer);
   const void* buf;
   int buf_len;
@@ -1739,13 +1739,14 @@ bool ParseSimpleStream(io::ZeroCopyInputStream& input_stream,
       continue;
     }
 
-    if (!parser.ParseChunk(StringPiece(static_cast<const char*>(buf), buf_len))) {
-      *out_error = ParserErrorString(parser, stream_name);
+    if (!parser.ParseChunk(StringPiece(static_cast<const char*>(buf), buf_len),
+                           &local_error)) {
+      *out_error = FullErrorString(stream_name, parser.last_line(), local_error);
       return false;
     }
   }
-  if (!parser.Finish()) {
-    *out_error = ParserErrorString(parser, stream_name);
+  if (!parser.Finish(&local_error)) {
+    *out_error = FullErrorString(stream_name, parser.last_line(), local_error);
     return false;
   }
   return true;

src/google/protobuf/compiler/objectivec/objectivec_helpers_unittest.cc

@@ -246,13 +246,16 @@ TEST(ObjCHelperDeathTest, TextFormatDecodeData_Failures) {
 class TestLineCollector : public LineConsumer {
  public:
   TestLineCollector(std::vector<std::string>* inout_lines,
-                    const std::string* reject_line = nullptr)
-    : lines_(inout_lines), reject_(reject_line) {}
+                    const std::string* reject_line = nullptr,
+                    bool skip_msg = false)
+    : lines_(inout_lines), reject_(reject_line), skip_msg_(skip_msg) {}
 
   bool ConsumeLine(const StringPiece& line, std::string* out_error) override {
     if (reject_) {
       if (*reject_ == line) {
-        *out_error = std::string("Rejected '") + *reject_ + "'";
+        if (!skip_msg_) {
+          *out_error = std::string("Rejected '") + *reject_ + "'";
+        }
         return false;
       }
     }
@@ -265,6 +268,7 @@ class TestLineCollector : public LineConsumer {
  private:
   std::vector<std::string>* lines_;
   const std::string* reject_;
+  bool skip_msg_;
 };
 
 const int kBlockSizes[] = {-1, 1, 2, 5, 64};
@@ -325,10 +329,10 @@ TEST(ObjCHelper, ParseSimple_DropsComments) {
 
 TEST(ObjCHelper, ParseSimple_RejectLines) {
   const std::vector<std::tuple<std::string, std::string, int>> tests = {
-    {"a\nb\nc", "a", 1},
-    {"a\nb\nc", "b", 2},
-    {"a\nb\nc", "c", 3},
-    {"a\nb\nc\n", "c", 3},
+    std::make_tuple("a\nb\nc", "a", 1),
+    std::make_tuple("a\nb\nc", "b", 2),
+    std::make_tuple("a\nb\nc", "c", 3),
+    std::make_tuple("a\nb\nc\n", "c", 3),
   };
 
   for (const auto& test : tests) {
@@ -338,7 +342,31 @@ TEST(ObjCHelper, ParseSimple_RejectLines) {
       std::string err_str;
       TestLineCollector collector(nullptr, &std::get<1>(test));
       EXPECT_FALSE(ParseSimpleStream(input, "dummy", &collector, &err_str));
-      std::string expected_err = StrCat("error: dummy Line ", std::get<2>(test), ", Rejected '", std::get<1>(test), "'");
+      std::string expected_err =
+        StrCat("error: dummy Line ", std::get<2>(test), ", Rejected '", std::get<1>(test), "'");
+      EXPECT_EQ(err_str, expected_err);
+    }
+  }
+}
+
+TEST(ObjCHelper, ParseSimple_RejectLinesNoMessage) {
+  const std::vector<std::tuple<std::string, std::string, int>> tests = {
+    std::make_tuple("a\nb\nc", "a", 1),
+    std::make_tuple("a\nb\nc", "b", 2),
+    std::make_tuple("a\nb\nc", "c", 3),
+    std::make_tuple("a\nb\nc\n", "c", 3),
+  };
+
+  for (const auto& test : tests) {
+    for (int i = 0; i < kBlockSizeCount; i++) {
+      io::ArrayInputStream input(std::get<0>(test).data(), std::get<0>(test).size(),
+                                 kBlockSizes[i]);
+      std::string err_str;
+      TestLineCollector collector(nullptr, &std::get<1>(test), true /* skip msg */);
+      EXPECT_FALSE(ParseSimpleStream(input, "dummy", &collector, &err_str));
+      std::string expected_err =
+        StrCat("error: dummy Line ", std::get<2>(test),
+               ", ConsumeLine failed without setting an error.");
       EXPECT_EQ(err_str, expected_err);
     }
   }