Not using the message service to add messages leads to less than desirable results

Problem/Motivation

Issue #3002571: Multiple warning messages when having untranslatable fields changed the way that we show messages to the user away from using the message service towards doing it directly in a render element. Whilst this does avoid the possibility of a message being repeated, it also means that the message appears in the content region, rather than whatever region the rest of messages are set to appear, leading to odd results.

See this example:

Steps to reproduce

1. Add some code that show a message on every page. In this example, is edited a module to print a warning on this page.
2. Enable the content translation module
3. Add a content type for translation and enable the "Hide non translatable fields on translation forms” option.
4. Add a language
5. Edit a piece of content and add a translation
6. Note the two messages appear in different parts of the page.

Proposed resolution

Unsure. Ideally, the message service would be able to properly handle messages added inside a form without them being repeated after submission. Does that even happen any more? I’ve not checked that yet.

Remaining tasks

Investigate options.

User interface changes

Introduced terminology

none

API changes

none

Data model changes

none

Release notes snippet