Nix formatting of multiline codeblocks is broken

[sumnerevans]

Steps to reproduce

Send a message with the following content to a room:

```nix
{
  foo = ''
    bar
  '';
}
```

What happened?

What did you expect?

I expect that the code block is shown correctly.

Operating system

NixOS

Application version

Element version: 1.8.2, Olm version: 3.2.3

How did you install the app?

NixOS/nixpkgs#136311

Homeserver

sumnerevans.com

Have you submitted a rageshake?

No

[robintown]

I cannot reproduce - could you paste the event's source, and also check whether "automatic language detection for syntax highlighting" is enabled in your preferences?

[sumnerevans]

I do have "Enable automatic language detection for syntax highlighting" on, but it also persists when it's disabled.

Here is the decrypted source for the message:

{
  "room_id": "!MahzEgrijBRaMQLBRS:matrix.org",
  "type": "m.room.message",
  "content": {
    "m.new_content": {
      "msgtype": "m.text",
      "body": "```nix\n{\n  foo = ''\n    bar\n  '';\n}\n```",
      "format": "org.matrix.custom.html",
      "formatted_body": "<pre><code class=\"language-nix\">{\n  foo = ''\n    bar\n  '';\n}\n</code></pre>\n"
    },
    "msgtype": "m.text",
    "body": " * ```nix\n{\n  foo = ''\n    bar\n  '';\n}\n```",
    "format": "org.matrix.custom.html",
    "formatted_body": " * <pre><code class=\"language-nix\">{\n  foo = ''\n    bar\n  '';\n}\n</code></pre>\n"
  }
}

[robintown]

Fixed by matrix-org/matrix-react-sdk#6681 (I mistakenly thought that this fix was already in 1.8.2, hence my confusion)