invalid configuration leads to crash

[mwermelinger]

If the configuration file is not valid JSON or if it doesn't include a LANGUAGE entry, then the program crashes. Tests need to be added.

While one could proceed with a missing LANGUAGE and simply report all constructs as disallowed, it's less baffling and more useful to report an error and exit.

Ideally, the JSON 'schema' should be checked and not just whether it has a LANGUAGE key. Is there a way?

[mwermelinger]

There is a JSON Schema specification that can be validated by jsonschema but I didn't look into details, e.g. how to specify that an object has integer keys. I used https://jsonschema.net to generate a schema from m269.json but it made each unit a mandatory property of each object, i.e. the schema included units 1, 2, 4, 8, etc. (whatever the JSON file had).

Given that in future we may move to TOML, which is easier to type and allows comments, it may be wise not to invest much effort into this.