Handle <ol start=…>

[gnprice]

An <ol> element in Zulip HTML can have the start attribute, like so:

<ol start="9999">
<li>Fjfjdj</li>
<li>Fjdjdj</li>
</ol>

On Zulip web, this renders like so:

(The fact that the numbers are cut off at the left is a bug that's getting fixed: zulip/zulip#25063.)

Currently we ignore start and always start the numbering at 1. We should instead respect start when we see it.

This means:

• When we parse the HTML, ListNode should get a bit more information to record start. Possibly make it abstract and give it subclasses OrderedListNode and UnorderedListNode, since start won't make sense on the latter.
• Then ListNodeWidget should act on that information.

[gnprice]

The Zulip Markdown message source that produces the example HTML above is:

9999. Fjfjdj
10000. Fjdjdj

[gnprice]

As part of this issue, the changes to HTML parsing should get tests in test/model/content_test.dart. This will probably involve adding another case to ContentNodeChecks.equalsNode (in content_checks.dart) for ListNode, similar to the existing case for ParagraphNode.

Ideally the changes to ListNodeWidget should also get tests, in test/widgets/content_test.dart. But we don't yet really have an example of that kind of test, so it's OK to leave that out for this issue. We have fewer examples of these, and I think that's a lower-priority test for this code (because that part seems less likely to later get broken by accident), so if that test feels hard to write then it's OK to leave it out for this issue.

(Edited 2023-07-10 with updates.)

[chrisbobbe]

This was reported as a bug in beta feedback: https://chat.zulip.org/#narrow/channel/48-mobile/topic/numbered.20lists.20rendering.20wrong/near/2018415

[lakshya1goel]

Hi, I have started working on this issue. Sharing the screenshots shortly.
Thanks!

[lakshya1goel]

Hi, I have raised PR #1329 for this issue, PTAL. Thanks!