`JSON::ResumableParser` swallows `ParserError` raised in `on_load`

[mame]

ResumableParser#parse swallows a JSON::ParserError raised inside on_load.

require "json"
parser = JSON::ResumableParser.new(on_load: ->(o) do
  JSON.parse("") #=> raises JSON::ParserError
  o
end)
parser << "[1]"
parser.parse
# expected: raises JSON::ParserError
# actual:   parse returns false (the error is swallowed)

This happens because the current implementation wraps parsing in rb_protect. Could exceptions raised inside on_load be re-raised? I'm a bit concerned about the overhead, though. If we do not, it would be good to document the behavior.

[mame]

Alternatively, the exception could also carry an @parser reference to the ResumableParser instance that raised it. Then #parse would swallow it only when it comes from that same @parser, and re-raise it otherwise. The overhead would not be big then.

[byroot]

Good catch.

the exception could also carry an @parser reference to the ResumableParser instance that raised it. Then #parse would swallow it only when it comes from that same @parser, and re-raise it otherwise. The overhead would not be big then.

Yes, I think that is the way.

Some initial version of ResumableParser tried to not raise errors for EOF and instead rely on json_parse_any returning false, but it made the happy path slower an more complicated, and ResumableParser#parse needed the rb_protect anyway because the parser may call into arbitrary Ruby because of on_load and decimal_class, so I figured we might as well.