Send email as plaintext

OK, I can understand the confusion, as the required code doesn't really exist yet!

I added a new section to the FAQ

This module is deeply based on Twig templates and rendering. These of course are HTML-based and they will persistently escape any plain text passed to them. So what we do is generate an HTML email then subsequently convert it to plain text.

Already the HtmlToTextEmailAdjuster generates the plain text alternative. So all that is left is to remove the HTML body, which is easy, just call setHtmlBody(NULL). You can do that in a postRender() function, but you must make sure your weight is >800 to come after HtmlToTextEmailAdjuster.

I have converted this to a "feature request". The task is to create a new EmailAdjuster implementation that does the above. Then it will be possible via the GUI with a policy element.

With the above, you would just call setBody(). I agree setTextBody() is tempting, but it has the following comment:

* By default, the text body will be generated from the unrendered body using
* EmailInterface::getBody(). This function can be used to set a custom
* plain-text alternative,

I've solved this for now using a hook:

In code, creating the email with

$email->setBody('Some basic plain text input');

Then the hook to remove the html and add the plain text.

/**
 * Implements hook_mailer_post_render().
 */
function MY_MODULE_mailer_post_render(\Drupal\symfony_mailer\EmailInterface $email) {
  // Only send as plain text.
  if ($email->getSubType() == 'SUBTYPE') {
    $email->setTextBody($email->getHtmlBody());
    $email->setHtmlBody(NULL);
  }
}

There is a variable is_html in the swiftmailer template (swiftmailer.html.twig)
I used this to manage HTML/plain text output in the template.
This is not set for the new email.html.twig
It was populated in the SwiftMailer.php plugin code.

It would be good to set this for symfony_mailer both for backward compatibility and native use.
However I can't see how a client module, via hooks, can get hold of both email object (to make a decision on whether to set is_html) and $variables at the same time (to set it)?

email.html.twig is similar to simplenews-newsletter-body.html.twig or commerce-order-receipt.html.twig - it creates a base email body

swiftmailer.html.twig is different - it wraps the above base email which is available as {{ body }}. It is similar to the template that would be added as part of #3271797: Wrap email body which would have the is_html variable.

Thanks @AdamPS
Lots of layers of this to try to figure out!

I've built a native implementation and added code as in #4

The symfony _mailer still sends text/plain and text/html sections (though the text/html is empty) (overall multipart/alternative).
My email client shows the empty body by default. Should the text/html be omitted if content is empty?

--5rFB3OrX
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
test body
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

--5rFB3OrX
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable

--5rFB3OrX--

Should the text/html be omitted if content is empty?

I guess that it is a matter of timing. Your hook will run run the default weight = 500. One of the adjusters such as AbsoluteUrlEmailAdjuster (weight = 700) runs afterwards and puts in an empty body.

You should make your code run with weight > 800, which makes it after HtmlToTextEmailAdjuster, then the plain text is already there (but better, as it calls Html2Text) and you can just call $email->setHtmlBody(NULL);. This way you will still get absolute URLs, which can be important. To create a hook with a specific weight, write a hook_mailer_TYPE__SUBTYPE_init() which calls email->addProcessor().

@AdamPS thanks
I see the issue but not sure how to change the weight.
I assume its my hook mymodule_mailer_post_render() code that needs to run later - but it sounds like its not the module weight you are referring to but the processor weight - which would be my EmailBuilderBase plugin?
I cant see how to do this with the hook you mention (ie on the $email object ).

it sounds like its not the module weight you are referring to but the processor weight -

Correct

I cant see how to do this with the hook you mention

It's not possible with the post_render hook. The easiest way is to create an email adjuster. I added an explanation to the issue summary "proposed resolution" section. It would be great if you could upload a patch if you get it working.

This EmailAdjuster has been disabled - the setting is now on WrapAndConvertEmailAdjuster.

Edit: see #3271797: Wrap email body