mailto: unable to correctly parse some URIs (e.g. lore.kernel.org)

[iam-TJ]

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There are PRs with fixes to some mailto parsing issues but this one seems to have escaped them! Discovered whilst trying to reply via mailto link in a Linux kernel mailing-list thread on lore.kernel.org; e.g:

https://lore.kernel.org/all/[email protected]/#t

In this case the link provided is:

<a
href="mailto:[email protected]?In-Reply-To=%[email protected]%3E&#38;Cc=andrea.righi%40canonical.com%2Cbluca%40debian.org%2Cckk%40debian.org%2Cdhowells%40redhat.com%2Cema%40debian.org%2Cericvh%40kernel.org%2Clinux-afs%40lists.infradead.org%2Clinux-cifs%40vger.kernel.org%2Clinux-fsdevel%40vger.kernel.org%2Clinux-kernel%40vger.kernel.org%2Clinux-mm%40kvack.org%2Clinux%40iam.tj%2Cv9fs%40lists.linux.dev&#38;Subject=Re%3A%20%5BPATCH%20v5%2040%2F40%5D%209p%3A%20Use%20netfslib%20read%2Fwrite_iter">mailto: link</a>

Using Firefox v128.0a1 amd64 on Debian GNU/Linux 12 Bookworm, this takes me via a "Switch" account intermediary page to:

https://mail.proton.me/u/1/inbox#mailto=mailto%3Aasmadeus%40codewreck.org%3FIn-Reply-To%3D%253CZnCviUrk5iQGrE4x%40codewreck.org%253E%26%2338%3BCc%3Dandrea.righi%2540canonical.com%252Cbluca%2540debian.org%252Cckk%2540debian.org%252Cdhowells%2540redhat.com%252Cema%2540debian.org%252Cericvh%2540kernel.org%252Clinux-afs%2540lists.infradead.org%252Clinux-cifs%2540vger.kernel.org%252Clinux-fsdevel%2540vger.kernel.org%252Clinux-kernel%2540vger.kernel.org%252Clinux-mm%2540kvack.org%252Clinux%2540iam.tj%252Cv9fs%2540lists.linux.dev%26%2338%3BSubject%3DRe%253A%2520%255BPATCH%2520v5%252040%252F40%255D%25209p%253A%2520Use%2520netfslib%2520read%252Fwrite_iter

but the resulting composer panel only has the To: field completed.

In particular I was expecting the Subject: and In-Reply-To: fields since that is how replies are threaded on lore.kernel.org but the BCc and Cc are also missing.