Stringifying an array of objects results in an error when its value is passed to another module

[maartenkools]

Bicep version 0.4.1272

Describe the bug Stringifying a locally defined array of objects results in an error about '{' being unexpected. Providing the array through a module does work.

To Reproduce Steps to reproduce the behavior:

var myArray = [
  {
    id: '117'
    name: 'John'
  }
]

// The module takes a string parameter called 'value'
module tst 'modules/sample-module.bicep' = {
  name: 'tst'
  params: {
    value: string(myArray)
  }
}

Error is:

{'code': 'InvalidTemplate', 'message': 'Deployment template language expression evaluation failed: \'The language expression \'{"id":"117","name":"John"}\' is not valid: the string character \'{\' at position \'0\' is not expected.\'. Please see https://aka.ms/arm-template-expressions for usage details.', 'additionalInfo': [{'type': 'TemplateViolation', 'info': {'lineNumber': 0, 'linePosition': 0, 'path': ''}}]}

However, if myArray is part of the output from another module, it does work as expected. So as a workaround I have a, pretty much, empty module returning an array of objects.

Additional context I'm trying to store an array of JSON objects in an App Configuration resource with the application/json content-type.

[alex-frankel]

Tested offline and the below code should work as a workaround:

// The module takes a string parameter called 'value'
module tst 'scratch-mod.bicep' = {
  name: 'tst'
  params: {
    value: ' ${string(myArray)}'
  }
}

This is related to service-side expression evaluation bug. When you converted the array into a string, the first and last characters are [ and ], which is considered an ARM Template expression, even though that is not what you are trying to express.

cc @majastrz as FYI

[maartenkools]

Tested offline and the below code should work as a workaround:

// The module takes a string parameter called 'value'
module tst 'scratch-mod.bicep' = {
  name: 'tst'
  params: {
    value: ' ${string(myArray)}'
  }
}

This is related to service-side expression evaluation bug. When you converted the array into a string, the first and last characters are [ and ], which is considered an ARM Template expression, even though that is not what you are trying to express.

cc @majastrz as FYI

That's a better workaround than using a module to provide the array. Important to note that the space in front is important, otherwise it leads to parse errors

[Rod-Sychev]

@alex-frankel Any ETA on the fix? BTW your workaround from the 9-March-2022 does not work when used in the resource:

param secrets array
param tags object
param keyVaultName string

resource keyVault 'Microsoft.KeyVault/vaults@2023-07-01' existing = {
  name: keyVaultName
}

resource kvsecrets 'Microsoft.KeyVault/vaults/secrets@2023-07-01'  = [for secret in secrets: {
  parent: keyVault
  name: secret.name
  tags: tags
  properties: {
    value: ' ${string(secret.value)}'
    attributes: {
      enabled: true
    }
  }
}]