Add JSON output to CLI pipeline validation

[colindean]

Description

The Vela CLI tool can validate .vela.yml but it just outputs an "it's ok" message when evaluating locally. It'd be great if it could output the config as JSON as seemingly the remote validation can.

Value

I'd like to extract information from .vela.yml via the commonly-installed jq program without having to install other tooling, e.g. yq or writing a script that converts YAML to JSON but does so without validation and with a different YAML parser that may produce a different JSON result than Go's YAML library that Vela uses.

My particular use case is extracting the Docker tag specified in the Vela config for use in a dev env build script.

Definition of Done

The vela validate pipeline program takes an option --output json when in local mode and produces a JSON version of the .vela.yml.

Impacted Personas (Optional)

Folks building tools around Vela would benefit from being able to deal with materialized JSON instead of YAML.

[benzvan]

I have also found that this it's ok message is returned even if the .vela.yml is not a yaml file.

[susangreve]

Thanks for opening this! We have added it to the backlog and will assess priority

[colindean]

Perhaps also an option to resolve templates, but with an acknowledgement that since templates can contain logic, they may not be expandable by the tool. I guess this could be worked around by allowing the user to specify environment variable values and telling the user what they need to supply when it's missing.

Bonus points if there's a way for Go templates to list what variables they expect…

[colindean]

The current behavior as of v0.17.0 now outputs the rendered template in YAML, but it also still outputs the "is valid" message, so piping the output to a yaml2json converter isn't possible without first removing the first line.

https://github.com/go-vela/cli/blob/641fb4c22d9e4ef1409ca564da665e322aa74931/action/pipeline/validate.go#L117-L126

[plyr4]

closed as complete via #791 and #313