Conditionally include a property

[mickybar]

I have a case where I want to conditionally omit a property for a resource.

I'd like to have that property set to false in certain conditions, but the property does not accept it. If it's present it needs to be true. If I want to set it to false, it has to be omitted altogether.

I am aware we can conditionally set a value for a property, but that does not apply in this case.

Is there a way to do this in bicep (or ARM)?

[alex-frankel]

Have you tried setting the value to null when the condition is false? This typically gets handled by the resource as if the property was not declared.

[mickybar]

Hi Alex,
brilliant, I didn't think about it. It worked

[JustinGrote]

@mickybar a lot of the tricks in ARM still work here, for instance using json('null') for complex object properties, or just '' for strings.

See my fortigate templte for a lot of example of conditional properties and settings/"knobs"
https://github.com/justingrote/fortigateazureha

[majastrz]

JSON now supports the null() function that should be used instead of json('null'). In bicep, the equivalent is the null keyword.

[JustinGrote]

I've tried it but have still had issues when supplying partial objects to configs like virtualmachines, and had to resort to json('null'), especially with conditionals.

EDIT: here's an example where only json('null') works. I forgot to show it here but null() isn't even a recognized bicep expression

Capture.mp4

[majastrz]

This is a bug in the type system. (null returns a value of type null and json('...') returns a value of any type, which is assignable to all types.) Can you open an issue for it and include the mp4?

The workaround that should work is any(null) in Bicep until we fix it.

[mickybar]

Thanks everyone for the suggestions. In my case I just needed a boolean value and using null in bicep made the trick