Query: Use jq to replace many values with variable values

(jump to the answer)

Using jq, is it possible to replace the value of each parameter in the sample JSON with the value of the variable that is the initial value?

In my scenario, Azure DevOps does not carryout any kind of variable substitution on the JSON file, so I need to do it manually. So for example, say $SUBSCRIPTION_ID is set to abc-123, I'd like to use jq to update the JSON file.

I can pull out the values using .parameters[].value, but I can't seem to find a way of setting each individual value.

The main challenge here is that the solution should be reusable, and different JSON files will have different parameters, so I don't think I can use --argjson.

Example

Original JSON

{
    "$schema": "https://schema.management.azure.com/schemas/2015-01-01/parametersTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "subscriptionId": {
            "value": "$SUBSCRIPTION_ID"
        },
        "topicName": {
            "value": "$TOPIC_NAME"
        }
    }
}

Variables

SUBSCRIPTION_ID="abc-123"
TOPIC_NAME="SomeTopic"

Desired JSON

{
    "$schema": "https://schema.management.azure.com/schemas/2015-01-01/parametersTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "subscriptionId": {
            "value": "abc-123"
        },
        "topicName": {
            "value": "SomeTopic"
        }
    }
}

A:

with jtc: iterate recursively over each value holding a substitution token (starting with $) and then replace it through shell evaluation:

bash $ <schema.json jtc -w'[value]:<^\$(.*)>R:' -eu echo '"${\$1}"' \;
{
   "$schema": "https://schema.management.azure.com/schemas/2015-01-01/parametersTemplate.json#",
   "contentVersion": "1.0.0.0",
   "parameters": {
      "subscriptionId": {
         "value": "abc-123"
      },
      "topicName": {
         "value": "SomeTopic"
      }
   }
}
bash $ 

- the solution is input-invariant (will work even if JSON is placed into another JSON container, or if values are scattered irregularly throughout JSON). - it's also resistant to partial substitutions.

To update the changes right into the file use -f option:

bash $ jtc -w'[value]:<^\$(.*)>R:' -eu echo '"${\$1}"' \; -f schema.json