New linter rule - use safe access

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: 05/06/2024
+ms.date: 07/19/2024
 ---
 
 # Add linter settings in the Bicep config file
@@ -121,6 +121,9 @@ The following example shows the rules that are available for configuration.
         "use-resource-symbol-reference": {
           "level": "warning"
         },
+        "use-safe-access": {
+          "level": "warning"
+        },
         "use-secure-value-for-secure-inputs": {
           "level": "error"
         },

articles/azure-resource-manager/bicep/linter-rule-use-safe-access.md

@@ -0,0 +1,107 @@
+---
+title: Linter rule - Use the safe access (.?) operator
+description: Use the safe access (.?) operator instead of checking object contents with the 'contains' function.
+ms.topic: conceptual
+ms.custom: devx-track-bicep
+ms.date: 07/19/2024
+---
+
+# Linter rule - use the safe access operator
+
+This rule looks for the use of the [`contains()`](./bicep-functions-object.md#contains) function for checking property existence before access and provides a simpler automatic replacement. It serves to recommend and introduce users to a simplified equivalent syntax without introducing any functional code changes. For more information, see [Safe dereference operator](./operator-safe-dereference.md).
+
+The specific patterns it's looking for are:
+
+- Ternary operator to check for property access:
+
+    ```bicep
+    contains(<object>, '<property>') ? <object>.<property> : <default-value>
+    ```
+
+    The following replacement is suggested:
+
+    ```bicep
+    <object>.?<property> ?? <default-value>
+    ```
+
+- Ternary operator to check for variable-named property access:
+
+    ```bicep
+    contains(<object>, <property-name>) ? foo[<property-name>] : <default-value>
+    ```
+
+    The following replacement is suggested:
+
+    ```bicep
+    <object>[?<property-name>] ?? <default-value>
+    ```
+
+## Linter rule code
+
+To customize rule settings, use the following value in the [Bicep configuration file](./bicep-config-linter.md):
+
+`use-safe-access`
+
+## Solution
+
+Accept the editor code action to automatically perform the refactor.
+
+## Examples
+
+### Named Property Access
+
+The following example triggers the rule:
+
+```bicep
+param foo object
+var test = contains(foo, 'bar') ? foo.bar : 'baz'
+```
+
+Accepting the code action results in the following Bicep:
+
+```bicep
+param foo object
+var test = foo.?bar ?? 'baz'
+```
+
+### Variable Property Access
+
+The following example triggers the rule:
+
+```bicep
+param foo object
+param target string
+var test = contains(foo, target) ? foo[target] : 'baz'
+```
+
+Accepting the code action results in the following Bicep:
+
+```bicep
+param foo object
+param target string
+var test = foo[?target] ?? 'baz'
+```
+
+### Non-issues
+
+The following examples don't trigger the rule:
+
+Difference between the property being checked and accessed:
+
+```bicep
+param foo object
+var test = contains(foo, 'bar') ? foo.baz : 'baz'
+```
+
+Difference between the variable property being checked and accessed:
+
+```bicep
+param foo object
+param target string
+param notTarget string
+var test = contains(foo, target) ? bar[notTarget] : 'baz'
+```
+
+## 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: 05/06/2024
+ms.date: 07/19/2024
 ---
 
 # Use Bicep linter
@@ -50,6 +50,7 @@ The default set of linter rules is minimal and taken from [arm-ttk test cases](.
 - [use-recent-api-versions](./linter-rule-use-recent-api-versions.md)
 - [use-resource-id-functions](./linter-rule-use-resource-id-functions.md)
 - [use-resource-symbol-reference](./linter-rule-use-resource-symbol-reference.md)
+- [use-safe-access](./linter-rule-use-safe-access.md)
 - [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)

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

@@ -549,6 +549,9 @@
       - name: Use resource symbol reference
         displayName: linter
         href: linter-rule-use-resource-symbol-reference.md
+      - name: Use safe access
+        displayName: linter
+        href: linter-rule-use-safe-access.md
       - name: Use secure value for secure inputs
         displayName: linter
         href: linter-rule-use-secure-value-for-secure-inputs.md