X-FHIR-Query support for variable extension

[FikriMilano]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #2075

Description

• Allows searching FHIR resources in variable-extension by using X-FHIR-Query
• When creating X-FHIR-Query from Expression, the code prioritize the pairs from variable-extension instead of from launch-context-extension, this is to prevents a bug mentioned in this comment
• Use suspend functions for all functions that are using/depends on variable extraction, since doing a variable extraction could cause a database operation that happens because of running the X-FHIR-Query

Alternative(s) considered
N/A

Type
Feature

Screenshots (if applicable)

Checklist

• I have read and acknowledged the Code of conduct.
• I have read the Contributing page.
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).

[santosh-pingle]

I am reviewing it, thanks!

[FikriMilano]

@santosh-pingle @jingtang10
Can we first merge #2066, before we merge this PR?

I am anticipating merge conflicts from #2066, so I pulled from there and integrate it in this PR.

And I would like to ensure that @MJ1998's contribution is duly noted from #2066.

[FikriMilano]

Todo:

1. refactor, think of ways on how the suspend function will work, in the context of enable when expression, because it uses the same evaluate method. Need to do this since enable when expression can access variable #2132 was merged
2. fix merge conflict from the same other PR enable when expression can access variable #2132

[FikriMilano]

@MJ1998 @omarismail94 this is ready for review

[MJ1998]

Thanks @FikriMilano

A few requests as this is difficult to follow:-

1. Could you resolve the comments.
2. Also could you describe your solution a little more in this PR's descripiton

[FikriMilano]

hold up, let me try to use _count, and see whether it can prevent the resolver to search everything, when there are no parameter values supplied

[FikriMilano]

ok, we don't need the hasMissingParamValue.
adding the query with the _count param would prevent the resolver to search everything.

Patient?name=&_count=2

[FikriMilano]

@MJ1998 @omarismail94
I've resolved the comments and updated the PR description

[jingtang10]

@omarismail94

there is a bug in createXFhirQueryFromExpression method.

where if we try to combine both fhirPathsEvaluatedPairs and variablesEvaluatedPairs, then fold the expression to replace the string template into the right evaluated value, the resulting xFhirQuery string gives the wrong result.

that happens because of the same variable name from both fhirPathsEvaluatedPairs and variablesEvaluatedPairs, and the variable from fhirPathsEvaluatedPairs are given first priority over the one from variablesEvaluatedPairs.

the one from fhirPathsEvaluatedPairs are empty, while what we need was from variablesEvaluatedPairs.

the resulting xFhirQuery has a search parameter, but that search parameter value is empty because of this. This will cause the fhirEngine resolver to search all resources of that type mentioned in the xFhirQuery. This can be prevented by using the _count param.

Example:

fhirPathsEvaluatedPairs contains: [{a}, “”] variablesEvaluatedPairs contains: [{a}, “47626”]

Resulting xFhirQuery: Patient?_id= The expected and correct xFhirQuery: Patient?_id=47626

Prevention 1, xFhirQuery: Patient?_count =1&_id= Prevention 2, xFhirQuery: Patient?_id=NOTHING

@FikriMilano can you create an issue here?

[FikriMilano]

@omarismail94
there is a bug in createXFhirQueryFromExpression method.
where if we try to combine both fhirPathsEvaluatedPairs and variablesEvaluatedPairs, then fold the expression to replace the string template into the right evaluated value, the resulting xFhirQuery string gives the wrong result.
that happens because of the same variable name from both fhirPathsEvaluatedPairs and variablesEvaluatedPairs, and the variable from fhirPathsEvaluatedPairs are given first priority over the one from variablesEvaluatedPairs.
the one from fhirPathsEvaluatedPairs are empty, while what we need was from variablesEvaluatedPairs.
the resulting xFhirQuery has a search parameter, but that search parameter value is empty because of this. This will cause the fhirEngine resolver to search all resources of that type mentioned in the xFhirQuery. This can be prevented by using the _count param.
Example:
fhirPathsEvaluatedPairs contains: [{a}, “”] variablesEvaluatedPairs contains: [{a}, “47626”]
Resulting xFhirQuery: Patient?_id= The expected and correct xFhirQuery: Patient?_id=47626
Prevention 1, xFhirQuery: Patient?_count =1&_id= Prevention 2, xFhirQuery: Patient?_id=NOTHING

@FikriMilano can you create an issue here?

here's the ticket #2451

[FikriMilano]

@jingtang10 this PR is ready to merge