[mu4e] set-email-account! does not set user-mail-address consistently

[wchmb]

I confirm that...

• I searched the FAQ, issue tracker, discussions board, documentation, and wiki, and found nothing about my issue.

• I read the debugging guide and researched the issue to the best of my ability.

• My issue can be observed on the latest available commit of Doom.

• My issue can be observed on a stable release of Emacs (i.e. doesn't end in .50, .60, or .9*)

Describe your issue

When using multiple email accounts with set-email-account! and (setq mu4e-compose-context-policy 'ask) the From header in the compose buffer does not always update to match the selected context.

The signature is correctly applied based on the chosen context, but the From header seems to retain the value of the default account.

Steps to reproduce

1. Set up two accounts. Mark one as the default.

(setq mu4e-compose-context-policy 'ask)

(set-email-account! "icloud"
  '((user-mail-address . "[email protected]")
    (user-full-name    . "My Name")
    (mu4e-compose-signature . "---\nSent from iCloud")
    )
  t) ;; Set iCloud as the default account

(set-email-account! "gmail"
  '((user-mail-address . "[email protected]")
    (user-full-name    . "My Name")
    (mu4e-compose-signature . "---\nSent from Gmail")
    ))

2. Start a new composition and select the non-default context (in this example, "gmail").

The mu4e compose buffer should open with the following headers and signature set according to the "gmail" context:

From: My Name <[email protected]>
To: 
Subject: 
--
---
Sent from Gmail

but instead, the From header is incorrectly set to the default "icloud" account:

From: My Name <[email protected]> 
To: 
Subject: 
--
---
Sent from Gmail

System information

https://gist.github.com/wchmb/38a7ff81dc599b3d1f3959ee0f455ce5