Add --context option to format.

[BigBlueHat]

Mainly, I wanted to be able to test JSON documents (which completely lack an @context property) by generating nquads and comparing that output as I change a local context file.

jsonld format -f nquads random.json --context=context.jsonld

[vorburger]

@BigBlueHat @davidlehn @msporny any chance you would consider merging this? I would use it on enola-dev/enola#779! 😺

[msporny]

@davidlehn any reason this PR is languishing? It feels fine to me. Can we merge it?

[davidlehn]

Does this work for compact and flatten? It's using the generic _jsonLdOptions() to set options.expandContext when --context is used. But compact and flatten already used --context to set the param for the API call. I'm not thinking this through all the way, but I don't think that will result in correct behavior. This perhaps need to be something like --expand-context and setup for all API calls that use that option.

[vorburger]

Actually I originally missed that this PR is specifically for adding --context to format, lint and expand; whereas I am using flatten which already has a --context flag... but you are right, it does not appear to work (on v2.0.0); if I (x2) remove this @context (as I will be in enola-dev/enola#796, WIP), then npx [email protected] flatten --context=test/picasso-context.jsonld test/picasso.json does NOT seem to read it (nor is there an error; it seems to just ignore it). Nor does npx [email protected] flatten --context=picasso-context.jsonld --base=test/ test/picasso.json work (re. #15). (With https://github.com/filip26/ld-cli it works, as used in tools/test-jsonld/test-jsonld.bash).

PS, just FYI: I had used jsonld-cli for exploring and learning JSON-LD, and am now moving on to using another implementation.