[FEATURE REQ] Support Parameters "allowedValues" property

[JohnathonMohr]

Please describe the feature or suggestion.

Template parameters can have an array defined specifying what values are allowed for the parameter.
https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/parameters#allowed-values

Currently, if a parameter has allowed values specified, template parsing (without using a parameters file) throws an exception because a mock value is used that (very likely) will not be an allowed value.

BPA should be able to pick a value from this list and use that for the parameter value instead of making up a value on its own.

Additional context

This could also be considered a bug, but I'm filing the issue as a feature request.

[pamelafox]

I ran into an issue with @Allowed parameters and am not sure if it's a bug with template-analyzer, a bug with our Bicep, or if it's this bug.

Specifically:

We have functions.bicep with these params:

// Runtime Properties
@allowed([
  'dotnet', 'dotnetcore', 'dotnet-isolated', 'node', 'python', 'java', 'powershell', 'custom'
])
param runtimeName string
param runtimeNameAndVersion string = '${runtimeName}|${runtimeVersion}'
param runtimeVersion string

https://github.com/Azure/azure-dev/blob/2545c2f84c0858d59b8df0c3c62bb733adbd4656/templates/common/infra/bicep/core/host/functions.bicep#L16

That runtimeName parameter gets passed into appservice.bicep, which has the same params declared:

// Runtime Properties
@allowed([
  'dotnet', 'dotnetcore', 'dotnet-isolated', 'node', 'python', 'java', 'powershell', 'custom'
])
param runtimeName string
param runtimeNameAndVersion string = '${runtimeName}|${runtimeVersion}'
param runtimeVersion string

https://github.com/Azure/azure-dev/blob/2545c2f84c0858d59b8df0c3c62bb733adbd4656/templates/common/infra/bicep/core/host/appservice.bicep#L15

The bicep checker is okay with this, but template-analyzer errors (fatally) and says:

    Error: An exception occurred while analyzing template /home/runner/work/simple-flask-server-example/simple-flask-server-example/infra/core/host/functions.bicep
    Exception details:
    Microsoft.Azure.Templates.Analyzer.Core.TemplateAnalyzerException: Error while evaluating rules.
     ---> Microsoft.Azure.Templates.Analyzer.Core.TemplateAnalyzerException: Error while processing template.
     ---> Azure.Deployments.Templates.Exceptions.TemplateValidationException: The provided value '[parameters('runtimeName')]' for the template parameter 'runtimeName' at line '1' and column '577' is not valid. The parameter value is not part of the allowed value(s): 'dotnet,dotnetcore,dotnet-isolated,node,python,java,powershell,custom'.

See full run: https://github.com/pamelafox/simple-flask-server-example/actions/runs/4492526898/jobs/7902534396?pr=3

Are we required to specify a default in functions.bicep for this scenario? Or is this a template-analyzer parsing issue? (And if so, is it the one described above?)

Thanks!

[mattcorr]

Any update on this? We are getting this issue as well when we have a parameter that needs to be a specific allowed value and if a parameter file is not provided the text generated does not match.