extracting path, method and content-type from swagger json with jq

Question

I already have a rough solution to this problem, but it's my first time working with JQ and I kind of feel like the result is a bit clunky, and I'd like advice on how to clean it up, or suggestions how I might use more idiomatic forms.

I have a swagger interface specification (full file here), and I want to extract info for each of the paths, the methods supported and the content-types expected in each case

For example, from:

{
   "paths" : {
      "/1.0/kb/paymentGateways/hosted/form/{accountId}" : {
         "post" : {
            "produces" : [
               "application/json"
            ],
            "consumes" : [
               "application/json"
            ]
      }
}

I would like to produce:

{
  "path": "/1.0/kb/paymentGateways/hosted/form/{accountId}",
  "method": "post",
  "produces": "application/json",
  "consumes": "application/json"
}

and here is the jq query I used to do this:

jq 'def nvl(n): (n//[null])[];'\
'.paths | keys[] as $path | .[$path] | keys[] as $method | .[$method] | '\
'{ $path, $method, produces: nvl(.produces), consumes: nvl(.consumes)}' swagger.json

Many Thanks

Answer 1

Apart from the formatting, you might consider defining nvl as a 0-arity filter (which is more idiomatic and more efficient) or avoiding it altogether. Assuming a bash or bash-like shell, you could write:

jq 'def nvl: (.//[null])[];
  .paths
  | keys_unsorted[] as $path
  | .[$path]
  | keys_unsorted[] as $method
  | .[$method]
  | { $path,
      $method,
      produces: .produces | nvl,
      consumes: .consumes | nvl
    }' swagger.json

Consider also using the -f command line option.

Note that false // 0 evaluates to 0, so you might want to modify the def accordingly. It might be wise also to guard against other potential surprises.