Incorrect help text for relation-get

[Kenneth Koski]

relation-get has this help text:

...
When reading remote relation data, a charm can call relation-get --app - to get
the data for the application data bag that is set by the remote applications
leader.
...

If I'm reading that correctly, I can run `relation-get --app -` to get the application data bag, but I get this error when attempting to run it inside of a hook:

    ERROR no unit or application specified

[Ian Booth (wallyworld)]

relation-get --app is the correct syntax
I assume it is being run inside a relation hook? Otherwise the -r arg is needed to explicitly specify the relation.

You get that error if the remote application that is at the other end of the relation is not yet available or not found.

You also get the same error without --app (querying unit relation data) if the other side is not available.

[Pen Gale (pengale)]

@wallyworld: are the caveats you mentioned documented anywhere? If so, I think that we can close this out as working as expected. If not, we probably need to either flesh out the documentation in the command's help, or document the gotchas elsewhere ...

[Ian Booth (wallyworld)]

It's not a gotcha that you get an error asking for something that's not there yet.
It's more that the error message is unhelpful and doesn't provide enough info to explain what the issue is.

[Jordan Barrett (barrettj12)]

In a debug-hooks session, I can't seem to get this working at all:
--------------------------------------------------
$ relation-get -
ERROR no relation id specified
$ relation-get - ds3/0
ERROR no relation id specified
$ relation-get - MYUNIT
ERROR no relation id specified
$ relation-get --app -
ERROR no relation id specified
$ relation-get --app
ERROR no relation id specified
--------------------------------------------------
Everything suggested in the help text/this bug report just gives me an error

[Jordan Barrett (barrettj12)]

Maybe we could have examples in the help text? I cannot for the life of me work out how to get useful output out of this command.
------------------------------------------------------
$ relation-get source:1
ERROR no relation id specified
$ relation-get -r 1
ERROR no unit or application specified
$ relation-get -r source:1
ERROR no unit or application specified
$ relation-get -r 1 source
ERROR no unit or application specified
------------------------------------------------------

[Jordan Barrett (barrettj12)]

Finally got some useful output from:
```
relation-get token -r $(relation-ids source) dummy-source/0
```
i.e.
```
relation-get -r <relation-id> <key> <unit>
```

[Canonical Juju QA Bot (juju-qa-bot)]

This Medium-priority bug has not been updated in 60 days, so we're marking it Low importance. If you believe this is incorrect, please update the importance.