Message.decode: Add max_recursion_depth option

This allows increasing the recursing depth from the default of 64, by
setting the "max_recursion_depth" to the desired integer value. This is
useful to parse complex nested protobuf messages that otherwise error out
with "Error occurred during parsing".

Fixes #1493

ruby/ext/google/protobuf_c/message.c

@@ -924,17 +924,39 @@ static VALUE Message_index_set(VALUE _self, VALUE field_name, VALUE value) {
  * format) under the interpretration given by this message class's definition
  * and returns a message object with the corresponding field values.
  */
-static VALUE Message_decode(VALUE klass, VALUE data) {
+static VALUE Message_decode(int argc, VALUE* argv, VALUE klass) {
+  VALUE data = argv[0];
+  int options = 0;
+
+  if (argc < 1 || argc > 2) {
+    rb_raise(rb_eArgError, "Expected 1 or 2 arguments.");
+  }
+
+  if (argc == 2) {
+    VALUE hash_args = argv[1];
+    if (TYPE(hash_args) != T_HASH) {
+      rb_raise(rb_eArgError, "Expected hash arguments.");
+    }
+
+    VALUE depth = rb_hash_lookup(hash_args, ID2SYM(rb_intern("max_recursion_depth")));
+
+    if (depth != Qnil && TYPE(depth) == T_FIXNUM) {
+      options = FIX2INT(depth) << 16;
+    }
+  }
+
   if (TYPE(data) != T_STRING) {
     rb_raise(rb_eArgError, "Expected string for binary protobuf data.");
   }
 
   VALUE msg_rb = initialize_rb_class_with_no_args(klass);
   Message* msg = ruby_to_Message(msg_rb);
 
-  if (!upb_decode(RSTRING_PTR(data), RSTRING_LEN(data), (upb_msg*)msg->msg,
-                 upb_msgdef_layout(msg->msgdef),
-                 Arena_get(msg->arena))) {
+  if (!_upb_decode(RSTRING_PTR(data), RSTRING_LEN(data), (upb_msg*)msg->msg,
+                  upb_msgdef_layout(msg->msgdef),
+                  NULL,
+                  options,
+                  Arena_get(msg->arena))) {
     rb_raise(cParseError, "Error occurred during parsing");
   }
 
@@ -1149,7 +1171,7 @@ VALUE build_class_from_descriptor(VALUE descriptor) {
   rb_define_method(klass, "to_s", Message_inspect, 0);
   rb_define_method(klass, "[]", Message_index, 1);
   rb_define_method(klass, "[]=", Message_index_set, 2);
-  rb_define_singleton_method(klass, "decode", Message_decode, 1);
+  rb_define_singleton_method(klass, "decode", Message_decode, -1);
   rb_define_singleton_method(klass, "encode", Message_encode, 1);
   rb_define_singleton_method(klass, "decode_json", Message_decode_json, -1);
   rb_define_singleton_method(klass, "encode_json", Message_encode_json, -1);

ruby/lib/google/protobuf.rb

@@ -67,8 +67,8 @@ def self.encode_json(msg, options = {})
       msg.to_json(options)
     end
 
-    def self.decode(klass, proto)
-      klass.decode(proto)
+    def self.decode(klass, proto, options = {})
+      klass.decode(proto, options)
     end
 
     def self.decode_json(klass, json, options = {})

ruby/tests/encode_decode_test.rb

@@ -101,4 +101,29 @@ def test_json_name
     assert_match json, "{\"CustomJsonName\":42}"
   end
 
+  def test_decode_depth_limit
+    msg = A::B::C::TestMessage.new(
+      optional_msg: A::B::C::TestMessage.new(
+        optional_msg: A::B::C::TestMessage.new(
+          optional_msg: A::B::C::TestMessage.new(
+            optional_msg: A::B::C::TestMessage.new(
+              optional_msg: A::B::C::TestMessage.new(
+              )
+            )
+          )
+        )
+      )
+    )
+    msg_encoded = A::B::C::TestMessage.encode(msg)
+    msg_out = A::B::C::TestMessage.decode(msg_encoded)
+    assert_match msg.to_json, msg_out.to_json
+
+    assert_raise Google::Protobuf::ParseError do
+      A::B::C::TestMessage.decode(msg_encoded, { max_recursion_depth: 4 })
+    end
+
+    msg_out = A::B::C::TestMessage.decode(msg_encoded, { max_recursion_depth: 5 })
+    assert_match msg.to_json, msg_out.to_json
+  end
+
 end