Alternative to JUTE $let derective proposal

[ir4y]

{
   "{% assign idQuestion %}": "patientId"
   "{% assign id %}": "{{ QuestionnaireResponse.repeat(item).where(linkId=%idQuestion).answer.valueString }}",
    "resourceType": "Bundle",
    "type": "transaction",
    "entry": [{
        "request": {
            "URL": "/Patient/{{ %id }}",
            "method": "PATCH"
        },
        "resource": {
            "{% assign phoneGroup %}": "{{ QuestionnaireResponse.repeat(item).where(linkId='phone-group') }}",
            "telecom": [
                {
                    "system": "phone",
                    "use": "{{ %phoneGroup.where(linkId='phone-type').answer.valueString }}",
                    "value": "{{ %phoneGroup.where(linkId='phone-number').answer.valueString }}"
                },
            ]
        }
    }]
}

[ir4y]

The order is not granted, so we have to build a dependency graph and evaluate it consequentially.

[ir4y]

As an alternative approach we can use an extension, please check #4 for more details.

[ir4y]

An alternative approach that fixes issues with ordering.
In this case {% let %} directive SHALL present only once on each level

With this approach, we can simplify this mapper even more

{
   "{% let %}": [
       {"idQuestion": "patientId"}, // Example of simple string
       {"qr": "{{ QuestionnaireResponse.repeat(item) }}"},
       {"id": "%qr.where(linkId=%idQuestion).answer.valueString }}"},
   ],                    
    "resourceType": "Bundle",
    "type": "transaction",
    "entry": [{
        "request": {
            "URL": "/Patient/{{ %id }}",
            "method": "PATCH"
        },
        "resource": {
            "{% let %}": [{"phoneGroup": "{{ $qr.where(linkId='phone-group') }}"}],
            "telecom": [
                {
                    "system": "phone",
                    "use": "{{ %phoneGroup.where(linkId='phone-type').answer.valueString }}",
                    "value": "{{ %phoneGroup.where(linkId='phone-number').answer.valueString }}"
                },
            ]
        }
    }]
}

[ruscoder]

The name {% assign %} is better than {% let %} to match the liquid naming.

Examples are available as tests here

FHIRPathMappingLanguage/ts/server/src/utils/extract.spec.ts

Line 284 in 35441b4

describe('Assign usage', () => {

[ruscoder]

The assign block might be defined in any other blocks including for (#1), merge (#7), if (#2) and it overrides local context for the block.