Changing original field option "Users may translate this field" should provide a content fallback

We encountered the same problem. I think this is a serious issue. When a site administrator changes field to translatable, they don't expect losing half (or more) of the field's data because of missing fallback...

Also encountered the same issue, seems pretty critical to me, I just wanted to enable translations for image ALT on an older site and all the translations (apart from the original language of the node) no longer have the image linked.

@ last reporters, can you please provide the Drupal version you have experienced your described issue?

I just wanted to enable translations for image ALT on an older site and all the translations (apart from the original language of the node) no longer have the image linked.

@honyik: The report is somewhat confusing me. If you just enabled translation for your entity type how can you have an original language and something like "all other translations"? Can you please describe the issue in more detail? THere is possible chance that your report describes another issue.

I will try to describe the real issue step by step:

- given a Drupal site with two languages, ie. English and Italian
- create a translatable content type
- create a field (ie. a plain text one) and leave it not translatable
- insert a content of the created one type in English language
- translate the inserted content in Italian
- make the privous created field translatable
- now value of the field made translatable is gone in the Italian content

Best would be a fallback in English

Observing changes in database after the field is made translatable it seems that providing a fallback it's really hard but a warning message at least should be shown when trying to make translatable a field with data in database.