Warn user when sync is enabled on field with previous values, they are not sync'd until one is changed

I followed steps 1-7 and get to this step:

Here's what I would propose for the warning text about fields being synchronized when values are edited: Disabling translation for this field will not delete the translated values. When the field value is edited in any language, all values for the field will be automatically synchronized.

However, when I go back to look at the field (step 9), the images do seem to be already synchronized (i.e. the French translation of the field is already deleted). Has the synchronization behaviour changed?

It may very well be that this is already fixed thanks to some other rework. Needs one more person to test I think.

I followed all the steps.
At Step 8 the message from #2 appears.
After confirming this dialog, all nodes are already synced. So Step 10 (save) is not needed.

But I did played a little bit around and came across some strange behaviour and have to look, if there are corresponding tickets open.
1. Even if I set Image - File as not translatable (only Titel and Alt of Image), I just could remove the Image at the translation, upload a new one and had two different images for the original and the translated node. Its seems to me, after I did this, I can't set Image to not translatable anymore. Batch job crashes, I need to investigate this further. (Could be "Drupal\Core\Entity\EntityStorageException: Missing bundle for entity type node in Drupal\Core\Entity\DatabaseStorageControllerNG->create() (Line 104 in .../core/lib/Drupal/Core/Entity/DatabaseStorageControllerNG.php).")
2. I didn't got the warning when enabling translation for one and disabling translation for another field and clicking on save in the translation settings. (/admin/config/regional/content-language)

Because of 2. I'll let this issue active, but I currently try it again on a fresh install, because of weired errors I'm getting (maybe because of 1.)

update:
1. Syncing works, if done after the initial translation. But when you create a translation you can change the image, even when image file is not translatable. Batch job to change the translatable state of images runs now for 20minutes and nothing happens, but no errors - cpu at 60%. No clue what is happening here.
2. The warning is completly not happening, when updating translatable at Content languaguage settings (/admin/config/regional/content-language)

Simple change in the title.

This will be reworked in the near future. We are planning to remove the data migration so this warning will not be meaningful any more. Refer to #2076445: Make sure language codes for original field values always match entity language regardless of field translatability for details.

We should have a viable solution in #2076445: Make sure language codes for original field values always match entity language regardless of field translatability that will let us switch field translatability without requiring a data migration, hence this UI will just go away. Postponing for now to wait to be sure this actually is the case.

Updated issue summary, fixed html ending tag for li

I'm going to try to reproduce this.
Conclusion:
Step 8, there is no warning (warning does not work)
Step 9 english and translated version are sync'd without changing one of them (sync works)

No warning presented on step 8. (though I don't recall applying a patch to add this behavior)

During my testing I made the body field and image file field translatable. After I followed step 7 to remove sync, the following happened when editing the node:

1. The default (english) translation looked fine as expected: http://note.io/1mXbIG0
2. The spanish translation body reverted back to english.
3. The spanish translation for the file image did NOT revert back to english version as seen here: http://note.io/1mXcJxT

On another note, the site cache needed to cleared in order to see the change when viewing the node regularly.

I also played around a little bit with this and found the behaviour for the image file is broken. The alt text and title work well, but if the 'File' checkbox is ticked the same image is used for the nodes in both languages. I also think it is strange to say a file is 'translatable'. I would prefer a help text saying something like 'Allow usage of different images in translations'.

After a clean install and enabling the Content Translation module the 'translate' tab is visible after creating a new article, even though I hadn't enabled any settings on admin/config/regional/content-language. When I click 'translate' there is no option to add a translation. This behaviour is a bit strange, I think. It would be better not to have the 'translate' tab if no element of the content type is configured for translations.

Here's a screenshot of what you see when the translatability of the content type 'article' has not been configured yet.

I have also played around with it, and noticed when the translation image overwrites the other language (for York for example it was not overwriting, weird..), then listing the content on the front page all link to the translated version (in my case http://localhost/drupal8/hu/node/3). The detection settings were the default (from URL). On the image my cursor was over the title of the English article, see the url in the bottom left corner.

Working on reproducing with Ryan Weal (mentor) help at Drupalcon Austin.

Confirmed issue still exists. Working on adding a warning when changing "configure Content Language Settings."

Added a warning message when an entity type is no longer set to translatable. It may need further work if this feature is required at the field level.

@Ryan Weal, I don't follow your solution. Can you give me more detail or hit me up on IRC (rbunch)?

Thank you for creating this issue to improve Drupal.

We are working to decide if this task is still relevant to a currently supported version of Drupal. There hasn't been any discussion here for over 8 years which suggests that this has either been implemented or is no longer relevant. Your thoughts on this will allow a decision to be made.

Since we need more information to move forward with this issue, the status is now Postponed (maintainer needs more info). If we don't receive additional information to help with the issue, it may be closed after three months.

Thanks!

Wanted to bump 1 more time, this actually seems like it would be a good feature and maybe priority normal vs minor?

Not comfortable closing this one moving back to NW.