Error handling and reporting

My philosophy so far has been to avoid runtime errors based on the shape of the context data wherever possible. Otherwise, it's very easy to take out large portions of a website when the context data is updated.

However, I think errors we can detect during compile time should be reported. In the JavaScript library, some of these might be best reported as warnings (or even console.errors for developers), to avoid breaking user interaction wherever possible. The server-side implementations should, however, produce exceptions in their normal way.

I'm opening this ticket in part to document my thoughts, but also to invite comment. If you think this is the wrong approach, let's discuss it here.

Start by reviewing the JavaScript library and the server-side implementations to identify errors detectable during compilation. Clarify which cases should be warnings or console errors in JavaScript and exceptions server-side, then document the expected behavior and agree on the scope before implementation.

Written by the indexing model from the issue text.