Directive does not update when switch from language with subset of overrides

[ach]

Subject of the issue

When switching from a language with a subset of overrides the non-overridden translation keys does not update in translate directive. Translate filter works as expected.

Your environment

• 2.15.2 angular-translate
• 1.6.3 angular
• Tests with Firefox 58b9 and Chrome 62.0.3202.94

Steps to reproduce

I have three languages: DE, EN and EN-US.

EN and DE have all language keys and translations.
EN-US only contain one override for key "hello", and fallback to EN.

https://plnkr.co/edit/M1VMVUgrKzq7gGaAaPpW?p=preview

Click on DE, paragraph is "Hier läuft..."
Click on en-US, paragraph is "This is runnin..."
Click on DE again, paragraph is still "This is runnin..."
Click on DE again, paragraph switches to correct value "Heir .."

Note: translate filter works as expected.

Expected behaviour

When i select DE after EN-US it should update language correctly to "Hier ..."

Actual behaviour

en-US language is still present for keys that is not overridden in en-US.

[knalli]

Quick solution: Despite the documentation, I would recommend setting the fallback in the config. It looks like it is a workaround for your issue.

I would recommend this also, but we should have a deeper look into it…