Hi David. Finally got back round to checking this with recent sw. Apologies
for the long delay. I can confirm that the problem still exists as before,
ie replying to my test html emails when composing the message in a new
frame throws the bodypart errors. ...But I'm not too fussed about it
because I've got used to not composing messages in new frames ;-)

I've synced my emacs.git to:
* c3ff6712ad -  (HEAD, origin/emacs-25) * lisp/net/tls.el (tls-program):
Fix :version (do not merge to master). (2017-09-14 16:38:29 -0400) <Glenn
Morris>

Emacs version is reported as 25.3.50.1.

And notmuch.git to:
* ab8b40f7 -  (HEAD -> master, origin/master, origin/HEAD) cli: make
notmuch count --exclude a boolean argument (2017-10-15 19:22:40 -0300)
<Jani Nikula>

Using the tiny .emacs below is enough to trigger the problem:

(require 'shr)
(setq mm-text-html-renderer 'shr)
(setq mime-view-text/html-previewer 'shr)
(setq mm-html-inhibit-images nil)
(setq mm-html-blocked-images nil)
(require 'notmuch)
(setq notmuch-mua-compose-in 'new-frame)
(setq notmuch-multipart/alternative-discouraged '("text/plain"))

Not sure what you'd like to do with this from here...
Cheers,
--  Matt

On Fri, Jun 30, 2017 at 1:47 PM, David Bremner <david@tethera.net> wrote:

> Matthew Lear <matt@bubblegen.co.uk> writes:
>
>
> > It was indeed fixed...that is until I updated my emacs git tree to
> 25.2.1.
> > I've given up composing emails in new frames as it's now broken again -
> > this time when replying to emails which have quoted/embedded html in the
> > body. Feels like two steps forward, one step back :-(
> > --  Matt
>
> Unfortunately I don't have easy access to emacs25.2; I've been waiting
> for it show up in Debian. Can you see if the relevant fix referenced in
> that bug log included in 25.2? I did wonder if maybe you had a local
> modification that was lost when you updated to 25.2.
>
> d
>