Built-in function to sort an array

[stan-sz]

Is your feature request related to a problem? Please describe.
Declarative deployments require consistent inputs for idempotency. I have a bicep template where a part of a blob name is computed using uniqueString(array). I'd like to ensure within the template that the array is always sorted to yield the same results for the same inputs.

Describe the solution you'd like
Given that ARM functions already have a defined compare functions, add a sort( function that would sort an array. Somewhat related to #2082

[majastrz]

We could be sorting arrays of objects with some properties or arrays of primitive types like strings or ints. How do you envision selecting the "key" for sorting the elements of the array?

[stan-sz]

I think the scope would be to write a meta sorting algorithm using the existing greater( or less( functions. It would be up to these functions to handle (or not) objects - the documentation and examples are missing this part. The selection whether to do ascending/descending order sorting could be a bool parameter of the sort function.
This also reminds me of #1427 to be able to iterate over dictionary keys in general.

[bmoore-msft]

@stan-sz - can you expand on the scenario a bit? JSON arrays are not sorted so the platform won't treat this consistently...

Also, as I understand your scenario, I'd just use a different / deterministic seed for the array.

[stan-sz]

Here's the detailed scenario: the Microsoft.ContainerRegistry/registries/pipelineRuns is used to transfer OCI artifacts (e.g. docker images, helm charts) from one container registry to another. One of the inputs is an array of to-be-transferred artifacts the other param is the name of the blob where the images will be exported to. uniqueString(array) is very handy to compute a unique blob name for the set of artifacts to be transferred.

The 'receiving' side of this pipeline needs to set the same blob name to trigger the import pipeline to get the images from the blob into the target container registry. Again, uniqueString(array) is handy in this case, as it returns the same unique string.

Currently a pre-deployment script is used to prepare the ARM parameters file based on user input (if the user wants to transfer a subset of images) to ensure the array is sorted. The user selects the images based on apps (each app consists of one or more images) and thus the array is the union of all images from selected apps.
With the sorting ability in Bicep, the whole logic of selecting a subset of images could be moved into the template and the user would interact only with the ARM deployment by passing the list of apps to transfer (the template would get as an input also the app->images mapping to do the image selection).