recently stopped working with Emacs

[archenemies]

I noticed that recently on various websites (including GitHub), Textern no longer works. I can open an editor, and any existing text in the text area shows up in the editor. However, changes made in the external editor are lost - they don't show up in the text area (and they don't seem to be preserved in any backup file).

[jlebon]

Did you change your editor configuration? Can you try the troubleshooting steps?

[archenemies]

OK thanks, you motivated me to do some troubleshooting. Below are my notes, but the summary is that the problem seems to have been caused by a recent Emacs upgrade (from 26.3 to 27.1). Unfortunately it is also dependent on my Emacs configuration, because when I start 27.1 with "-q", which skips reading my configuration, then Textern still works.

• Not dependent on Firefox version

• Not dependent on GitHub, even a barebones HTML with textarea exhibits problem

• I tried downgrading Systemd as well, no luck

• I change my editor configuration all the time, but not in a way that should have mattered. An old configuration still exhibits the bug

• This works (from the troubleshooting guide):

  ["sh", "-c", "echo foobar > $0"]
  

I wasn't sure about $0 so I also checked that this works:

  ["sh", "-c", "echo foobar > %s"]

I use a custom script that invokes Emacs via "emacsclient -nw" in an X terminal window. It doesn't exit until I close the editor. I get the same behavior with either of these configured as the Textern editor:

["my-x-editor", "+%l:%c"]
["my-x-editor", "+%l:%c", "%s"]
["my-x-editor", "%s"]

In "about:debugging > Textern" I find "Uncaught (in promise) Error: Missing host permission for the tab, and any iframes".

• I used git to pull the latest version of Textern, reinstall as both user and root, same problem.

• While I am editing a textarea, I find textern is running:

  $ ps aux | grep textern
  me   14466  1.0  0.2  99532 16968 ?        SNl  11:26   0:00 python3 /home/me/.local/libexec/textern/textern.py /home/me/.mozilla/native-messaging-hosts/textern.json textern@jlebon.com
  me   14467  0.0  0.0  10640  3952 ?        SN   11:26   0:00 /bin/zsh /home/me/scripts-misc/my-x-editor +1:1 /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt
  me   14469  0.0  0.0   9556  3692 ?        SN   11:26   0:00 /bin/sh /home/me/scripts-misc/urxvtc-wait em +1:1 /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt
  me   14471  0.0  0.0   9556  3084 pts/22   SNs+ 11:26   0:00 sh -c "$@"; kill -USR1 14469 x em +1:1 /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt
  me   14473  0.0  0.0   9556  3100 pts/22   SN+  11:26   0:00 /bin/sh /home/me/scripts-misc/em +1:1 /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt
  me   14474  0.0  0.0   2360   712 pts/22   SN+  11:26   0:00 emacsclient -c -nw +1:1 /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt
  me   14510  0.0  0.0   8688  2388 pts/23   SN+  11:26   0:00 grep textern
  

After saving, I find that the file /run/user/1000/textern/textern-8k75mahh/localhost%2F~me%2Fm.html-ui74e8v5.txt contains the desired text. But it doesn't show up in the textarea.

• Browser console (Ctrl+Shift+J) shows the following errors:

  sendRemoveListener on closed conduit textern@jlebon.com.549755813890 ConduitsChild.jsm:108
      _send resource://gre/modules/ConduitsChild.jsm:108
      _send self-hosted:1275
      removeListener resource://gre/modules/ExtensionChild.jsm:663
      removeListener resource://gre/modules/ExtensionChild.jsm:886
      onChanged chrome://extensions/content/child/ext-storage.js:337
      removeListener resource://gre/modules/ExtensionCommon.jsm:2517
      revoke resource://gre/modules/ExtensionCommon.jsm:2539
      close resource://gre/modules/ExtensionCommon.jsm:2544
      unload resource://gre/modules/ExtensionCommon.jsm:909
      close resource://gre/modules/ExtensionContent.jsm:927
      destroyed resource://gre/modules/ExtensionContent.jsm:1005
      observe resource://gre/modules/ExtensionContent.jsm:1023
  

• Changing the configured editor: Gedit works, "Emacs -q" works:

  ["my-x-editor", "%s"] -> doesn't work
  ["gedit"] -> works
  ["urxvtc-wait","emacs","-nw","-q"] -> works (`-q` keeps it from reading startup file)
  ["urxvtc-wait","emacs","-nw"] -> doesn't work, even when reverting to old `~/.emacs` and old `~/.emacs.d`
  

• Original configuration works after downgrading Emacs:

  # works:
  sudo pacman -U /var/cache/pacman/pkg/emacs-26.3-2-x86_64.pkg.tar.zst
  # doesn't work:
  sudo pacman -U /var/cache/pacman/pkg/emacs-27.1-2-x86_64.pkg.tar.zst