metadata cli: support JSON-formatted output

Some CLIs (docker comes to mind) support optional JSON-formatted output to allow for programatic result processing to automate certain tasks, such as testing, migration etc. It would be nice if elyra-metadata would support a flag (for example) that the user can specify to have the results returned as a JSON document, which can be easily parsed using jq.

Example of current output:

$ elyra-metadata list code-snippets
Available metadata instances for code-snippets (includes invalid):

Schema         Instance   Resource                                                            
------         --------   --------                                                            
code-snippet   a          /Users/patti/Library/Jupyter/metadata/code-snippets/a.json          
code-snippet   aaa        /Users/patti/Library/Jupyter/metadata/code-snippets/aaa.json        
code-snippet   b          /Users/patti/Library/Jupyter/metadata/code-snippets/b.json          
code-snippet   c          /Users/patti/Library/Jupyter/metadata/code-snippets/c.json          
code-snippet   copyright  /Users/patti/Library/Jupyter/metadata/code-snippets/copyright.json  
code-snippet   s          /Users/patti/Library/Jupyter/metadata/code-snippets/s.json      

vs

$ elyra-metadata list code-snippets --format JSON
[
  {
    ...
  },
 {
   ...
  }
]

[kevin-bates]

I didn’t see the option when I tried 1.0.0 b1 and don’t recall it being mentioned in the change log.

No worries - the option has been there since the tool existed.

I’m in favor of changing the functionality of --json so that it ONLY displays JSON (as array elements) and tolerates being piped to JSON-aware tools.

@lresende - are you okay with that?

[ptitzler]

If we add these to the Metadata class…

from elyra.metadata import MetadataManager
print(MetadataManager('code-snippets').get_all())

A programming language agnostic approach would be more user friendly.