Dynamic answerExpression not working

[FikriMilano]

Describe the bug
answerExpression doesn’t support accessing context from variable expression, it only can for launch context. This makes it not possible to have dynamic answer options.

So basically, the answer options within the dropdown widget is static once the app render the questionnaire.

Component
SDC library

To Reproduce
Steps to reproduce the behavior:

1. Paste the downloaded sample Questionnaire into demo app assets folder
2. Replace the file name in the following line of code to 'dynamic-answer-expression.json'
   https://github.com/google/android-fhir/blob/master/demo/src/main/java/com/google/android/fhir/demo/EditPatientViewModel.kt#L48
3. Run demo app, and wait for sync
4. Click a patient
5. Click edit icon (top-right corner)
6. In the first dropdown, select the "NAIROBI" city
7. Open the second dropdown
8. It still shows nothing

Expected behavior
answerExpression should be able to access other context including variable expression, therefore making the answer options dynamic, every time the variable updates.

Screenshots

device-2023-06-30-181824.webm

Smartphone (please complete the following information):

• Device: [e.g. Pixel4a emulator]
• Android version: [e.g. Settings -> About phone -> Android version]
• Build number: [e.g. Settings -> About phone -> Build number]
• Version [e.g. 22]

Additional context

• Sample Questionnaire, download below:
  https://drive.google.com/file/d/1aweK2JZ-3dzG9N7M2KoPwy_80sqZF9my/view?usp=sharing
• The cqf-expression extension within the sample, serve as a prove that the variable expression DOES updates and you can see it in the second dropdown question title. But the answerExpression DOES NOT update.
• FHIR doc of answerExpression: https://build.fhir.org/ig/HL7/sdc/StructureDefinition-sdc-questionnaire-answerExpression.html
• More FHIR doc of answerExpression: https://build.fhir.org/ig/HL7/sdc/expressions.html#answerExpression
• In this case, answerExpression is retrieving a list of Patient from local db, then display it in the dropdown as answer options
• The code you probably need to look at: https://github.com/google/android-fhir/blob/master/datacapture/src/main/java/com/google/android/fhir/datacapture/QuestionnaireViewModel.kt#L585-L589

Would you like to work on the issue?
N/A

[MJ1998]

Hey @FikriMilano Could you give an example ?

[FikriMilano]

@MJ1998 thank you so much for the interest!
I added the sample questionnaire, demo video, and more details in the ticket description.

[FikriMilano]

Hi @MJ1998
Kindly let me know if you have any follow up questions

[FikriMilano]

@f-odhiambo @pld

[MJ1998]

Hi @FikriMilano
Sure. Thanks for adding a detailed description.

[FikriMilano]

@MJ1998 just to make sure, I would like to inquire whether you are currently working on this task. If not, I would be happy to pick this up, as it holds high priority for our team.

[MJ1998]

Yes @FikriMilano, I am working on this. I hope a solution by tomorrow should be good ? If its urgent then please feel free to take this up.

[FikriMilano]

That's great news! thank you @MJ1998 :D

Tomorrow is fine, please continue. It would be a shame if your 1 week of efforts is not getting merged. Looking forward for your code, thanks :D

[MJ1998]

Alright I have a crude working solution. There are 2 errors:

1. answerExpressionMap stores initial expression and does not re-evaluate
2. variables in x-fhir-query are not supported, only launchContext

Crude solution is to bypass 1 and replace variables in fhir-query expression with values evaluated.

But from the other PR's comment you tagged me, it seems its better to modify the QuestionnaireViewItem API with enabledAnswerOptionList .

[FikriMilano]

@MJ1998 thanks for the update.

Can you create a PR for the crude solution? I would like to review the code and test it on my end to determine if it can serve as a temporary solution. However, it is not necessary to merge it into the master branch. If we find it suitable, my team can pull the branch to our fork and proceed with our own release.

For the better solution, we can create a separate branch for it, as I agree with @jingtang10's suggestion. Since FHIR provides multiple methods for adding answer options to an item, do you have an estimate for how long it will take to implement the better solution?

[MJ1998]

@FikriMilano There you go!
Will fix the tests soon.

[FikriMilano]

Thanks @MJ1998 :D
I'll review it.