gencli: warnings from staticcheck

[timburks]

We recently ran the staticcheck linter on our project and found that some warnings were produced for generated CLI code.

apigee/registry#744
apigee/registry#746
apigee/registry#748
apigee/registry#749
apigee/registry#750

These look like reasonable (but admittedly low-priority) improvements to make, and each seems potentially tricky enough to warrant a separate PR. Would PRs addressing them be welcome? These might be good first issues for newcomers interested in the project.

[noahdietz]

Hey, yeah PRs would be welcome. I think all are worth addressing.

apigee/registry#744 I'm a little unsure about since the error strings get dumped to the command line, and are not part of a "Go library". Would you rather see a capitalized error message on console, or no?

[timburks]

Here's what we're seeing for an error in the generated code:

$ registry rpc create-api --parent projects/one/locations/global --api.labels foo --api_id=test
Error: Invalid map item: "foo"
Usage:
  registry rpc create-api [flags]

[[ flag info deleted ]]

Invalid map item: "foo"

and this is what we show for an error from our API:

$ registry rpc create-api --parent projects/one/locations/global
Error: required flag(s) "api_id" not set
Usage:
  registry rpc create-api [flags]

[[ flag info deleted ]]

required flag(s) "api_id" not set

The error is printed twice - the second time, we're explicitly printing it (maybe we shouldn't /cc @seaneganx, @theganyo). But the first printing, which I think is from Cobra, seems to be consistent with what the linter is suggesting.