Potential risk of not working get_block or get_block_header_state

[conr2d]

@arhag

As you know, I wrote the patch for fc which throws an exception when the length of hex string (for vector<char>) is not even number. However, I found the risk that this patch makes RPC API get_block or get_block_header_state not work when it is merged to EOS repository.

In chain_plugin.cpp:

   try {
      block = db.fetch_block_by_id(fc::variant(params.block_num_or_id).as<block_id_type>());
      if (!block) {
         block = db.fetch_block_by_number(fc::to_uint64(params.block_num_or_id));
      }

} EOS_RETHROW_EXCEPTIONS(chain::block_id_type_exception, "Invalid block ID: ${block_num_or_id}", ("block_num_or_id", params.block_num_or_id))

In second line, there's no try-catch block for fc::variant(params.block_num_or_id).as<block_id_type>(), but when params.block_num_or_id is block_num (not block_id), and the number of its digits is odd, it throws an exception instead of executing db.fetch_block_by_number().

I think there can be several solutions for this.

1. Add try-catch block in chain_plugin
2. Allow odd-number length hex string
3. Revert patch for simplicity (!)

I think the first solution is correct, but I can't assure that there will be no part written like this. The second solution seems safer.

[arhag]

This was already fixed in PR #6904.

[conr2d]

@arhag Oh, God. I didn't knew it. I was worried my patch might cause some trouble. Thanks. :)