contact_mail() casts rendered markup to string

Removed string cast.

#2506581: Remove SafeMarkup::set() from Renderer::doRender introduced those string casts.

Initially, that patch did not add this string cast. Only since #2506581-44: Remove SafeMarkup::set() from Renderer::doRender, it does. Because since that iteration of the patch, renderPlain() is returning SafeStringInterface (by now MarkupInterface).

The only reason AFAICT that we added that string cast, is to keep BC.

But perhaps in this particular instance, that was not necessary.

We should get Alex Pott's thoughts on this.

But overall, +1, because That breaks sending HTML mails for example with swift mailer, which tries to be correct and escapes non-safe HTML. sounds sensible, and due to this string cast, that mailer cannot detect that this is in fact already considered safe.

Agreed with #6.

Assigning to @alexpott so he knows this is waiting on him.

Isn't there an issue with what is considered safe for email being different from html. As far as I can remember, these string casts occurred so that there was no unnecessary API change - maybe something will break now this is an object?

Thinking so more - I'm generally happy that we should delay the string casting. But this needs to be documented on hook_mail(). In an ideal world mail sending would leverage the render system and then we'd delay everything including the render here.

@Berdir thanks that is exactly what I was expecting.

It is shame we don't have anywhere we document some of the expectations around the API but it is not up to this issue to fix that.

+++ b/core/core.api.php
@@ -1947,9 +1947,10 @@ function hook_queue_info_alter(&$queues) {
+ *     An array of strings or objects that implement MarkupIntrface containing

s/MarkupIntrface/MarkupInterface/

Can be fixed on commit.

I fixed up the docs to have fqcn...

diff --git a/core/core.api.php b/core/core.api.php
index 5dcb798..27bc96d 100644
--- a/core/core.api.php
+++ b/core/core.api.php
@@ -1947,10 +1947,10 @@ function hook_queue_info_alter(&$queues) {
  *     Subject of the email to be sent. This must not contain any newline
  *     characters, or the email may not be sent properly.
  *  - 'body':
- *     An array of strings or objects that implement MarkupIntrface containing
- *     the message text. The message body is created by concatenating the
- *     individual array strings into a single text string using "\n\n" as a
- *     separator.
+ *     An array of strings or objects that implement
+ *     \Drupal\Component\Render\MarkupInterface containing the message text. The
+ *     message body is created by concatenating the individual array strings
+ *     into a single text string using "\n\n" as a separator.
  *  - 'headers':
  *     Associative array containing mail headers, such as From, Sender,
  *     MIME-Version, Content-Type, etc.
@@ -2000,7 +2000,8 @@ function hook_mail_alter(&$message) {
  *   - body: An array of lines containing the message to be sent. Drupal will
  *     format the correct line endings for you. MailManagerInterface->mail()
  *     sets this to an empty array when the hook is invoked. The array may
- *     contain either strings or objects implementing MarkupInterface.
+ *     contain either strings or objects implementing
+ *     \Drupal\Component\Render\MarkupInterface.
  *   - from: The address the message will be marked as being from, which is
  *     set by MailManagerInterface->mail() to either a custom address or the
  *     site-wide default email address when the hook is invoked.

Discussed with @xjm and @catch and we agreed this was eligible for inclusion in 8.1.x.

Committed 2ef41bb and pushed to 8.1.x and 8.2.x. Thanks!