For the record, this parser implements CommonMark Spec, with only some GFM extensions (that are optional but enabled by default). I would prefer to stay strict on this (and similar "softenings" of restrictions that make parsing easier).

But CommonMark also specifies that whitespace after closing fences are to be ignored, so this should be fixed (here). PR welcome!

I can confirm that this also happens when the closing fence is followed immediately by EOF. That's an easier scenario to catch than trailing whitespace, so I might open a PR for that case specifically.

I can confirm that this also happens when the closing fence is followed immediately by EOF. That's an easier scenario to catch than trailing whitespace, so I might open a PR for that case specifically.

If that's easy, a fix there would be awesome, because I think that's probably a more common scenario than trailing whitespace, though obviously both would be nice to have

I would think both should be a fairly easy fix, no? I might be missing something, but it looks like we could just check for end of file or space in addition to \r and \n in