fix gfm extended autolinking requiring multiple backpedals

[Trott]

Marked version:

0.4.0

Markdown flavor:

GitHub Flavored Markdown

Description

Add a test and fix that trailing punctuation is omitted in link URLs for
markdown like this:

(See https://www.example.com/fhqwhgads.)

The trailing period and closing parenthesis should not be part of the
link URL.

Expectation

<p>(See <a href="https://www.example.com/fhqwhgads">https://www.example.com/fhqwhgads</a>.)</p>

Result

<p>(See <a href="https://www.example.com/fhqwhgads.">https://www.example.com/fhqwhgads.</a>)</p>

Note that the trailing period is included as part of the URL. That's the bug.

Contributor

• Test(s) exist to ensure functionality and minimize regression (if no tests added, list tests covering this PR); or,

Committer

In most cases, this should be a different person than the contributor.

• Draft GitHub release notes have been updated.
• CI is green (no forced merge required).
• Merge PR

[UziTech]

Don't include changes to marked.min.js in this PR. It is generated automatically on merge.

Other than that LGTM

[Trott]

@UziTech I've backed out the change to marked.min.js.

[Feder1co5oave]

A possessive quantifier to eat all the trailing punctuation in the backpedal regex would fix this very elegantly, unfortunately there is scarce support for them in regex engines.
This looks like a decent workaround for that.

Suggestion: have you tested the behavior of the current and proposed backpedaling algorithm with maliciously long sequences of trailing punctuation in a gfm autolink?
The backpedal regex should always match, and it shouldn't backtrack except for the corner case of this issue where multiple punctuation is found at the end, where only one additional step should be required to match up until the second-last character, is my guess.

[davisjam]

Not sure why this line is here? Seems to duplicate the next line.

[Trott]

It's a copy/paste from elsewhere in the same file. See lines 53 and 68. I'll remove them all.

[davisjam]

On the theme suggested by @Feder1co5oave, @Trott can you add tests for a URL inside nested parentheses?

((http://foo.com))
((http://foo.com.))

[Trott]

On the theme suggested by @Feder1co5oave, @Trott can you add tests for a URL inside nested parentheses?

((http://foo.com))
((http://foo.com.))

@davisjam Done.

[Trott]

Suggestion: have you tested the behavior of the current and proposed backpedaling algorithm with maliciously long sequences of trailing punctuation in a gfm autolink?

@Feder1co5oave I'm not sure what would constitute "maliciously long" in this instance. Can you provide an example or a description? And would it be reasonable to include one in the specs?

[Martii]

@Trott
I believe it's about a ReDoS vector with dynamic input.

Let's see how GH handles that (don't mind the below... meant as a test only... not to annoy... EDIT don't want to overload the url in the demos).

(See https://www.example.com/fhqwhgads.......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................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Okay that should be enough to test although probably not a ReDoS equivalent (add a few million to see for sure but won't do that here). 😸

[Martii]

Interesting... autolinking doesn't appear to work like this right now:

Excessive periods

(See https://www.example.com/fhqwhgads.......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................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Does any markdown work inside HTML tags here? (should be bold)

[Trott]

Does any markdown work inside HTML tags here? (should be bold)

@Martii My understanding of markdown specs is that markdown is not expanded inside block elements.

[Martii]

@Trott

My understanding of markdown specs is that markdown is not expanded inside block elements.

So it looks like GH GFM may have a bug too since it's bolding and italicizing.

Ex.

**This is inside a p HTML tag and should not be bolded**

Gotta love md implementations sometimes. 😸 Thanks for the tip to look for.

[Trott]

@Martii Doesn't look buggy to me!

Inside a <p> element so should not bold:

**Look! No bold!!**

Not inside a <p> element so should bold:

Very bold!

[Trott]

Is there anything else that needs to happen to this before it can be merged? Not pushing for it to happen now now now or anything, but if there's something that's waiting on me, I'd like to address it.

[Martii]

@Trott
Look inside the comment dropdown details at #1293 (comment) Keeping in linear context is key with the prior comment from you. So yes it is bolding and italicizing currently... which is why I said italicizing so you wouldn't get confused. Guess that didn't work.

[Trott]

Ex. seemed like it was short for Example of the bug I just described in the previous sentence, but it's followed by correct (as far as I can tell?) rendering. That was the source of my misunderstanding.

I see now that in the <details> section, there is bolding and italicizing but not autolinking. I suppose that's a bug, although I guess GitHub gets to write whatever rules they want for GFM, so maybe that's the correct spec behavior in some weird way. I'm kidding. Maybe. I guess there's also the fact that <details> is non-standard to begin with, so maybe all bets are off anyway. At this point, though, I'm just making stuff up so maybe it's best if I stop typing since I'm almost certainly wrong about at least four things in this paragraph. Hope this was at least mildly entertaining.

EDIT: Yep, I'm wrong about <details> being non-standard, guess that happens when you don't write HTML for about 10 years...

[styfle]

@davisjam I think your comments were addressed, correct?
Anything else needed before we merge this?