Support evaluation of FHIRPath expressions and calculation within Questionnaire

[fredhersch]

Is your feature request related to a problem? Please describe.
There is a need to be able to evaluate expressions within a Questionnaire. This is currently not supported by the data-capture library

Describe the solution you'd like
Support for FHIRPath expressions

Describe alternatives you've considered
Other options include CQL.

Additional context
@maimoonak - can you provide some example use cases for the types of expressions you are trying to evaluate

[maimoonak]

There are multiple requirements we figured out when working on Family Registration. These are broken down in branch https://github.com/google/android-fhir/blob/mssng-quest-feat and commit

EnableWhen is not working fully - FHIR Reference

EnableWhen on answerInteger (crashes when value input for integer field)
kotlin.NotImplementedError: Enable when operator GREATER_OR_EQUAL is not implemented.
Sample Questionnaire crashes here

Alternate enableExpression is also not working
An alternate is to use enableExpression which also does not work and can be seen here

Hidden is partially working

"hidden": true - still not working - see here
extension hidden - "http://hl7.org/fhir/StructureDefinition/questionnaire-hidden" is working - see here

choice-orientation = horizontal - not working

see here

Slider not working - FHIR Reference

Exmple can be seen here

readonly not working

see example here

calculated-expression and variable not working - FHIR Reference

see example where we want to take age OR birthdate as input and calculate the other from one which was input here

You can run app from branch and see different questionnaires created

@f-odhiambo @fredhersch

[jingtang10]

Thanks for this @maimoonak. I'll use this comment to track the issues you raised (I'll cross out items that have been triaged):

• EnableWhen is not working fully GREATER_OR_EQUAL tracked in Implement inequality operators (<, >, <=, >=) in the enable when statement #818
• Alternate enableExpression is also not working tracked in Support enableWhenExpression #819
• Hidden is partially working Jing: there is only an extension: http://build.fhir.org/ig/HL7/sdc/rendering.html#hidden I don't see the hidden field in the questionnaire definition. So I think the usage here is incorrect - you need to use the extension.
• choice-orientation = horizontal - not working tracked here Horizontal layout support for RadioGroup and CheckBoxGroup #586
• Slider not working - FHIR Reference Slider Widget is not working #828
• readonly not working tracked here Add readOnly itemControl support #763
• calculated-expression and variable not working - FHIR Reference tracked in Support calculatedExpression #971

[fredhersch]

@jingtang10 @maimoonak For slider not working is this issue relevant? #201

cc: @f-odhiambo

[maimoonak]

@fredhersch @jingtang10 The issue above was for adding a slider widget which apparently is present in library, however, I could not figure out if it is added to widgets adapter. There is no reference to this widget except in unit test, so I think that its implementation is not complete. Please check ticket here for details #828

The class src/main/java/com/google/android/fhir/datacapture/QuestionnaireItemAdapter.kt initialize and bind different widgets but no reference of QuestionnaireItemSliderViewHolderFactory was found in this class or anywhere else except in a unit test

[jingtang10]

thansk @maimoonak -- yeah i can see the issue.

all issues you raised have tracking issues now as listed in the comment above.

[maimoonak]

@jingtang10 here is the expression context variable protocol. http://build.fhir.org/ig/HL7/sdc/expressions.html#fhirpath-supplements

[maimoonak]

@jingtang10 I could not figure out calculated-expression and variable - FHIR Reference that this issue is tracking into roadmap here. Could you please guide which point reflects this and if this is under progress.

[jingtang10]

@maimoonak - given that all the other issues are being tracked/closed i'm goign to close this bug. For the issue with enable when expressions let's continue the discussion in #819