Evaluating command inside JQ pipeline - jq

Question

I'm struggling evaluating a command inside a jq pipeline. Example will make it easier. Let's imagine I've got this simple json
{
"model": [{
"id": "an-id",
"path": [
"mypath1.txt"
],
"model": "foo"
},
{
"id": "an-id2",
"path": [
"mypath1.txt"
],
"model": "foo2"
}
]
}
And I want to convert into this
{
"model": [{
"id": "an-id",
"path": [
"mypath1.txt"
],
"model": "foo",
"alternative_model": "I am a computed value out of <foo>"
},
{
"id": "an-id2",
"path": [
"mypath1.txt"
],
"model": "foo2",
"alternative_model": "I am a computed value out of <foo2>"
}
]
}
I want to do something like this that allows me to delegate computing alternative model to a different bash script.
myNewJson=$(cat mappings.json | jq '[.model[]| {
id: .id,
path: .path
model: .model
alternative_model: //TODO}' ---> here I'd like to do something like "eval ./myscript $model"
])
Thanks!

Answer 1

Let's assume myscript contains following line :
echo "I am a computed value out of <$1>"
As jq does not allow to evaluate shell commands, you need something like :
#!/usr/bin/env bash
input=mappings.json
alternative-models(){
local result='{}' sres
for id in $(jq -r '.model[].id' $input); do
model="$(jq -r --arg id "$id" '.model[]|select(.id==$id).model' $input)"
amodel="$(./myscript $model)"
result="$(jq --arg id $id --arg amodel "$amodel" '. + { $id: $amodel }' <<< "$result")"
done
echo "$result"
}
jq --argjson amodels "$(alternative-models)" '.model|map({
id, path, model, "alternative_model": $amodels[.id] }
)' $input
Your mappings.json is not valid json because of a comma on the model line.