Linter rule - use explicit values for module location parameters

This rule finds module parameters that are used for resource locations and may inadvertently default to an unexpected value.

Linter rule code

Use the following value in the Bicep configuration file to customize rule settings:

explicit-values-for-loc-params

Solution

When you consume a module, any location-related parameters that have a default value should be assigned an explicit value. Location-related parameters include parameters that have a default value referencing resourceGroup().location or deployment().location and also any parameter that is referenced from a resource's location property.

A parameter that defaults to a resource group's or deployment's location is convenient when a bicep file is used as a main deployment template. However, when such a default value is used in a module, it may cause unexpected behavior if the main template's resources aren't located in the same region as the resource group.

Examples

The following example fails this test. Module m1's parameter location isn't assigned an explicit value, so it defaults to resourceGroup().location, as specified in module1.bicep. But using the resource group location may not be the intended behavior, since other resources in main.bicep might be created in a different location than the resource group's location.

main.bicep:

param location string = 'eastus'

module m1 'module1.bicep' = {
 name: 'm1'
}

resource storageaccount 'Microsoft.Storage/storageAccounts@2024-03-01' = {
  name: 'storageaccount'
  location: location
  kind: 'StorageV2'
  sku: {
    name: 'Standard_LRS'
  }
}

module1.bicep:

param location string = resourceGroup().location

resource stg 'Microsoft.Storage/storageAccounts@2024-03-01' = {
  name: 'stg'
  location: location
  kind: 'StorageV2'
  sku: {
    name: 'Premium_LRS'
  }
}

You can fix the failure by explicitly passing in a value for the module's location property:

main.bicep:

param location string = 'eastus'

module m1 'module1.bicep' = {
  name: 'm1'
  params: {
   location: location // An explicit value will override the default value specified in module1.bicep
  }
}

resource storageaccount 'Microsoft.Storage/storageAccounts@2024-03-01' = {
  name: 'storageaccount'
  location: location
  kind: 'StorageV2'
  sku: {
    name: 'Standard_LRS'
  }
}

Next steps

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