Specify when (if ever) parsers should give up

[anko]

@jgm @Hoylen Thanks for your inputs! (No pun intended.)

It seems we have an obvious conclusion to “should parsers give up”: they shouldn’t—all inputs are valid. So I’ve created a pull request to clarify the spec.

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As for null (U+0000) characters:

@Hoylen

Perhaps the presence of U+0000 can be pushed outside the scope of CommonMark? Anko could define the behaviour of his “bytes to characters” converter to flag U+0000 as invalid input, before it is passed to the CommonMark parser.

That seems to be the current situation. I’m OK with that. “The parser always succeeds” is a really strong guarantee. I wouldn’t want to dull it by making it conditional on whether the input includes null characters.

@Hoylen

What does “replace the Unicode character” mean: replace it with what? To avoid confusion, how are making “must strip” the only way to handle U+0000?

I wondered that too. But since it’s a separate issue, let’s take that to a new topic.