I just noticed that all installed languages are displayed, however if “pivot” models are not installed it can cause this error
Example of installed models:
- en → es
- es → en
- en → nl
The nl → es translation will therefore not work because no model is installed for
- @dingedi
I noticed en->ca is currently broken with a similar issue on libretranslate.com. This is occuring because ca->en is installed so English and Catalan are displayed in the user interface as available then fail when you try to translate English to Catalan.
We should figure out a good way to deal with this type of issue. In future versions of Argos Translate I’m planning to move to multilingual models so this should happen less frequently.
I think the best solution is probably to have a better error response at the API level and more descriptive feedback in the graphical user interface.
We could have a language_pairs endpoint that returns something like this:
[[en, ca],[ca,en],[en,es]]
One issue with this approach is that this list could become very long if we want to support 200+ languages in the future. The list would be O(n^2) for the number of languages n so 200^2=40000. I don’t think this is a huge deal though, if the response is less than 1MB lots of other web applications are downloading larger JavaScript tracking scripts 
. However searching this list might be slow.
Another solution would be to add an API endpoint to check if a specific language pair is supported. This could be a standalone endpoint or we could add functionality to mark an API request as a test and get a response telling you if it’s a valid request.