new linter rule - what-if-short-circuiting

Author: mumian

articles/azure-resource-manager/bicep/bicep-config-linter.md

@@ -3,7 +3,7 @@ title: Linter settings for Bicep config
 description: Describes how to customize configuration values for the Bicep linter
 ms.topic: conceptual
 ms.custom: devx-track-bicep
-ms.date: 07/30/2024
+ms.date: 09/19/2024
 ---
 
 # Add linter settings in the Bicep config file
@@ -135,6 +135,9 @@ The following example shows the rules that are available for configuration.
         },
         "use-stable-vm-image": {
           "level": "warning"
+        },
+        "what-if-short-circuiting": {
+          "level": "warning"
         }
       }
     }

articles/azure-resource-manager/bicep/linter-rule-what-if-short-circuiting.md

@@ -0,0 +1,82 @@
+---
+title: Linter rule - what-if short circuiting
+description: Linter rule - what-if short circuiting
+ms.topic: reference
+ms.custom: devx-track-bicep
+ms.date: 09/19/2024
+---
+
+# Linter rule - what-if short circuiting
+
+This rule detects runtime values used to determine resource IDs within modules and flags potential what-if short-circuiting.
+
+> [!NOTE]
+> This rule is off by default, change the level in [bicepconfig.json](./bicep-config-linter.md) to enable it.
+
+## Linter rule code
+
+Use the following value in the [Bicep configuration file](bicep-config-linter.md) to customize rule settings:
+
+`what-if-short-circuiting`
+
+## Solution
+
+This rule checks for runtime values that are used to determine resource IDs from within modules. It lets you know if your Bicep file will cuase what-if short circuiting. In the following example, **appServiceOutputs** and **appServiceTests** would both be flagged for what-if short circuiting becasue they pass runtime values as a parameter to the module which uses that when naming the resource:
+
+This rule checks for runtime values used to determine resource IDs within modules. It alerts you if your Bicep file could cause what-if short-circuiting. In the example below, **appServiceOutputs** and **appServiceTests** would be flagged for what-if short-circuiting because they pass runtime values as parameters to the module, which uses them when naming the resource:
+
+**main.bicep**
+
+```bicep
+resource storageAccount 'Microsoft.Storage/storageAccounts@2023-05-01' = {
+  name: 'storageAccountName'
+  location: 'eastus'
+  sku: {
+    name: 'Standard_LRS'
+  }
+  kind: 'StorageV2'
+}
+
+module appServiceModule 'modules/appService.bicep' = {
+  name: 'appService2'
+  params: {
+    appServiceName: 'test'
+  }
+}
+
+module appServiceOutputs 'modules/appService.bicep' = {
+  name: 'appService3'
+  params: {
+    appServiceName: appServiceModule.outputs.outputName
+  }
+}
+
+module appServiceTest 'modules/appService.bicep' = {
+  name:'test3'
+  params: {
+    appServiceName: storageAccount.properties.accessTier
+  }
+}
+```
+
+**modules/appService.bicep**
+
+```bicep
+param appServiceName string
+
+resource appServiceApp 'Microsoft.Web/sites@2023-12-01' = {
+  name: appServiceName
+  location: 'eastus'
+  properties: {
+    httpsOnly: true
+  }
+}
+
+output outputName string = 'outputName'
+```
+
+To avoid this issue, use deployment-time constants for values that are used in determining resource IDs.
+
+## Next steps
+
+For more information about the linter, see [Use Bicep linter](./linter.md).

articles/azure-resource-manager/bicep/linter.md

@@ -3,7 +3,7 @@ title: Use Bicep linter
 description: Learn how to use Bicep linter.
 ms.topic: how-to
 ms.custom: devx-track-bicep
-ms.date: 07/30/2024
+ms.date: 09/19/2024
 ---
 
 # Use Bicep linter
@@ -55,6 +55,7 @@ The default set of linter rules is minimal and taken from [arm-ttk test cases](.
 - [use-secure-value-for-secure-inputs](./linter-rule-use-secure-value-for-secure-inputs.md)
 - [use-stable-resource-identifiers](./linter-rule-use-stable-resource-identifier.md)
 - [use-stable-vm-image](./linter-rule-use-stable-vm-image.md)
+- [what-if-short-circuiting](./linter-rule-what-if-short-circuiting.md)
 
 You can customize how the linter rules are applied. To overwrite the default settings, add a **bicepconfig.json** file and apply custom settings. For more information about applying those settings, see [Add custom settings in the Bicep config file](bicep-config-linter.md).
 

articles/azure-resource-manager/bicep/toc.yml

@@ -563,6 +563,9 @@
       - name: Use stable VM image
         displayName: linter
         href: linter-rule-use-stable-vm-image.md
+      - name: What-if short-circuiting
+        displayName: linter
+        href: linter-rule-what-if-short-circuiting.md
   - name: Deploy
     items:
     - name: What-if check