non-compact list turned into compact list when editing a sent message

[Flupp]

Steps to reproduce

Send a message containing a non-compact list:

A list:

- item 1

- item 2

Then click on the edit button for that message.

Outcome

What did you expect?

Markdown source with a non-compact list:

A list:

- item 1

- item 2

What happened instead?

Markdown source with a compact list:

A list:

- item 1
- item 2

Note that compact and non-compact lists are rendered differently.

Although already closed, issues #20073 and #13474 might be related.

Operating system

Arch Linux

Application version

element-desktop 1.11.0-1

How did you install the app?

Pacman / official Arch Linux repositories

Homeserver

No response

Will you send logs?

No

[robintown]

Regressed by matrix-org/matrix-react-sdk#8004

[andybalaam]

Hopefully if we'd written the right test in matrix-react-sdk/test/editor/roundtrip-test.ts we would have caught this - when we fix it I suggest adding one (if I'm right).

[robintown]

We actually used to have a test for this in test/editor/deserialize-test.js, but I removed it in that PR because the syntax it expected still didn't actually parse as a non-tight list under Commonmark

[t3chguy]

Duplicate of #10725