Being able to reference resources across modules?

[anthony-c-martin]

There's a lot of useful stuff you can do once you have a symbolic reference to a resource - property access, proper type validation, deploying extension resources, deploying child resources, and probably some other things I'm not thinking of. This is at odds with reference() and resourceId(), which give you untyped objects and strings respectively.

It's great that we have these capabilities within one file, but it feels a bit limiting that they are confined to within that file. This limits my ability to modularize my code.

For example being able to define a reusable template that deploys an extension resource:

// main.bicep

resource myParent 'My.Rp/parent@2020-01-01' = {
  ...
}

module deployExtensions './extensions.bicep' = {
  ...
  params: {
    // pass the ref to the parent
    parent: parent
  }
}

// access the ref for the extension resource
var extensionRef = deployExtensions.outputs.extension1

// extensions.bicep

// mockup for a resource reference parameter
param parent resource<'My.Rp/parent@2020-01-01'>

// access properties from parent with type safety
var myParentProp = parent.properties.foo

// deploy an extension resource
resource extension1 'My.OtherRp/extension@2020-01-01' = {
  scope: parent
  ...
}

// mockup to output the resource reference
output myExtension resource<'My.OtherRp/extension@2020-01-01'> = extension1

Just wanted to start a discussion to see if this is potentially interesting to anyone, there are any potential other use-cases that I haven't thought of, or workarounds to do something similar today!

[majastrz]

I think overall the scenario is super useful and we should support it. One big unknown in my mind right now is how we approach visibility of exported resources. Do we make that explicit or do we just expose everything? Based on feedback, I think we have users in both camps.

[ChristopherL-STCU]

I just ran up against this limitation as well. I also prefer the explicit approach.

[erapade]

After my first learning session I started to write my own first deployment and guess what… I couldn’t reference a resource in another module :-). Maybe it’s a beginner mistake to modulate to much, but this would be really good.

Concerning implicit or explicit, the answer is probably found in the question “What is the problem with implicit?” From a re-use perspective, why should a module creator need to enable this feature? So I vote for implicit

[anthony-c-martin]

FYI - we are planning to do this under #2246.

[brwilkinson]

marking as answered based on it being tracked/discussed in #2246

[aviita]

I worked around this by keeping everything (regarding front door) in one file and resorting to looping.

Though it would seem that one obvious workaround would be to use the existing keyword with getting hold of resource that has already been created in parent script. See docs for Existing resources in Bicep. I have not tested this one though yet.

param parentResourceName string 

resource parentResource 'Microsoft.Storage/storageAccounts@2019-06-01' existing = {
  name: parentResourceName 
}