Using Jq

[globalflea]

i am new to Jq expression and the command line tool. Would appreciate help with this.
In the spec, an example is given under the Action Data Filter section with the following:

{ "actions":[
    {  "functionRef": "breadAndPastaTypesFunction",
       "actionDataFilter": { 
           "results": "${ [ .breads[0], .pasta[1] ] }",
          "toStateData": "${ .itemsToBuyAtStore }"
       }     }   ] }

I was trying to use the jq tool to try evaluating the "results" filter, but somehow can't get the jq tool to parse the expressions, for example:

echo '{ "breads": ["baguette", "brioche", "rye"], "pasta": [ "penne",  "spaghetti", "ravioli"] }' | jq '${ [ .breads[0],  .pasta[1] ] }'

gives the following error:

jq: error: syntax error, unexpected '{', expecting IDENT or __loc__ (Unix shell quoting issues?) at <top-level>, line 1:
${ [ .breads[0],  .pasta[1] ] }
jq: 1 compile error

and it seems in the jq website the example use of "$" is given as below to create a variable which is used subsequently

length as $array_length | add / $array_length

[tsurdilo]

expression syntax in serverless workflow:
${ expression }

this is the syntax regardless of expression lang used.

so try running the actual expression inside

[globalflea]

Oh apologies, I was stuck at the v0.6 spec and I thought the spec was giving an example of the jq expression rather than stating that jq expression are embedded within "${}". But isn't this sort of unnecessary, given that we are expecting jq expression already - ie why do we need this extra markers?

[ricardozanini]

In some fields, we accept static strings and expressions, so the ${} helps the runtime implementation to differentiate them. In this case, it is always an expression, but we kept this way to keep the cohesion within the workflow definition.