Compacting failure with @vocab

[Fak3]

from pprint import pprint
ctx = {'@vocab': 'http://ex.org/#', 'path': {'@type': '@id'}}
data = {
    'http://ex.org/#maxCount': 1,
    'http://ex.org/#path': 'http://ex.org/#shortname'
}
pprint(jsonld.compact(data, ctx))
# {
#   '@context': {'@vocab': 'http://ex.org/#', 'path': {'@type': '@id'}},
#    # NOTE: maxCount: not declared in context => compacted OK
#   'maxCount': 1
#    # NOTE: path: declared in context => compacting FAILED
#   'http://ex.org/#path': 'http://ex.org/#shortname',
# }

[Fak3]

One interesting doscovery: if i change 'http://ex.org/#shortname' to {'@id': 'http://ex.org/#shortname'} in the input data json, then property name compaction suddenly works, but the property value still not compacted:

{'@context': {'@vocab': 'http://ex.org/#', 'path': {'@type': '@id'}},
 '@id': '_:b0',
 'maxCount': 1,
 'path': 'http://ex.org/#shortname'}
# Note: `path` is compacted, but its value still isn't

[mielvds]

I think this is expected behaviour. Compaction expands the term first, so http://ex.org/#path expands as a plain string value, not an @id. Hence, 'http://ex.org/#path': 'http://ex.org/#shortname' becomes "http://ex.org/#path": [{"@value": "http://ex.org/#shortname"}].
That's also why changing 'http://ex.org/#shortname' to {'@id': 'http://ex.org/#shortname'} generates a different outcome.

This would be different if the context would be part of the input document:

data = {
    '@context': {'@vocab': 'http://ex.org/#', 'path': {'@type': '@id'}},
    'http://ex.org/#maxCount': 1,
    'http://ex.org/#path': 'http://ex.org/#shortname'
}

The playground seems to behave the same way: https://json-ld.org/playground/next/#json-ld=%7B%22http%3A%2F%2Fex.org%2F%23maxCount%22%3A1%2C%22http%3A%2F%2Fex.org%2F%23path%22%3A%22http%3A%2F%2Fex.org%2F%23shortname%22%7D&context=%7B%22%40context%22%3A%7B%22%40vocab%22%3A%22http%3A%2F%2Fex.org%2F%23%22%2C%22path%22%3A%7B%22%40type%22%3A%22%40id%22%7D%7D%7D&startTab=tab-compacted

I added a test-case in #262