HTML comments in middle of block

[mikesamuel]

Motivation

Comments in Markdown aren't really a thing, but they can come in super-useful. As alluded to in the test-case, MOE can be used to sync between internally developed projects and open-source versions. Part of that requires maintaining internal & external developer docs. MOE directives in comments make that a lot easier, but if they can't appear in the middle of a bullet list that becomes a lot harder.

---

Current Behavior

src/document.c recognizes <!--...--> style comments as a standalone block.

src/smarty_pants.c seems to recognize them anywhere though I haven't tested.

Changes

This adds a test-case and tweaks document.c to copy HTML comments over the same way it copies tags over.

The HTML comment recognizing code is a bit of a copy/paste job from parse_htmlblock but that version does a bunch of extra work. I can factor out the common code if you'd like.

[mikesamuel]

commonmark example-567 says the markdown

foo <!-- this is a
comment - with hyphen -->

corresponds to the HTML

<p>foo <!-- this is a
comment - with hyphen --></p>

[mildsunrise]

The v3 codebase is no longer in development other than for fixes, but/so I think a change like this one is acceptable.

However, your code isn't very legible and it seems to trigger an out-of-bounds read when the closing --> is not found. (i.e. control continues, the rest of the function executes with i > size)

[mildsunrise]

Sorry, I spoke two early! The conditional on the next line completely resets i so it's okay.
If @devinus agrees, we can merge this.

[mikesamuel]

I was unaware that there is a newer version. Should I try to effect a similar change in the dev version? Where would I find that?

[mikesamuel]

Would you like a testcase for -- at the end of input?

[devinus]

This is a good fix IMO.

[mildsunrise]

Okay, about to merge.

Would you like a testcase for -- at the end of input?

No, it's good. Our handling of comments isn't HTML compliant anyway.

I was unaware that there is a newer version. Should I try to effect a similar change in the dev version? Where would I find that?

No worries, the dev version targets CommonMark compliance, and it already parses HTML comments, both inline and block.

[mildsunrise]

Released v3.0.6 with this and #174.