Create rule S6952: Redundant explicit dependencies between resources …

…should be removed

rules/S6952/azureresourcemanager/metadata.json

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+{
+  "title": "Redundant explicit dependencies between resources should be removed",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-6952",
+  "sqKey": "S6952",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "HIGH",
+      "RELIABILITY": "MEDIUM",
+      "SECURITY": "LOW"
+    },
+    "attribute": "CONVENTIONAL"
+  }
+}

rules/S6952/azureresourcemanager/rule.adoc

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+In Azure Resource Manager (ARM) templates, dependencies between resources can be defined in two ways: implicitly or explicitly. We recommend not adding explicit dependencies when they are already defined implicitly to avoid redundancy and make the template more straightforward to read.
+
+== Why is this an issue?
+In Azure Resource Manager (ARM) templates, dependencies between resources can be defined in two ways: implicitly or explicitly. An implicit dependency is set when you use the `reference` function and pass in the resource name. An explicit dependency is defined when you add a `dependsOn` element. However, a code smell arises when these dependencies are used simultaneously for the same resources. This redundancy is unnecessary and can lead to confusion. Therefore, to maintain clarity and efficiency in your code, it is best to omit explicit dependencies when they are already defined implicitly.
+
+== How to fix it in ARM templates
+
+If a resource references another with a `reference` function, remove the `dependsOn` element if it points to the same resource.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,json,diff-id=1,diff-type=noncompliant]
+----
+{
+  "apiVersion": "2019-04-01",
+  "type": "Microsoft.Network/networkInterfaces",
+  "name": "exampleNic",
+  "location": "[resourceGroup().location]",
+  "dependsOn": [
+    "[resourceId('Microsoft.Network/virtualNetworks', 'exampleVNet')]"
+  ],
+  "properties": {
+    "ipConfigurations": [
+      {
+        "name": "ipconfig1",
+        "properties": {
+          "subnet": {
+            "id": "[reference('Microsoft.Network/virtualNetworks/exampleVNet/subnets/exampleSubnet').id]"
+          }
+        }
+      }
+    ]
+  }
+}
+----
+
+==== Compliant solution
+
+[source,json,diff-id=1,diff-type=compliant]
+----
+{
+  "apiVersion": "2019-04-01",
+  "type": "Microsoft.Network/networkInterfaces",
+  "name": "exampleNic",
+  "location": "[resourceGroup().location]",
+  "properties": {
+    "ipConfigurations": [
+      {
+        "name": "ipconfig1",
+        "properties": {
+          "subnet": {
+            "id": "[reference('Microsoft.Network/virtualNetworks/exampleVNet/subnets/exampleSubnet').id]"
+          }
+        }
+      }
+    ]
+  }
+}
+----
+
+== How to fix it in Bicep
+If a resource references another resource by a symbolic name or with a `reference` function, remove the `dependsOn` element if it points to the same resource. Note: Bicep provides the reference function, but in most cases, the symbolic name should be preferred over it.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,bicep,diff-id=2,diff-type=noncompliant]
+----
+resource exampleVNet 'Microsoft.Network/virtualNetworks@2020-06-01' existing = {
+  name: 'exampleVNet'
+}
+
+resource exampleSubnet 'Microsoft.Network/virtualNetworks/subnets@2020-06-01' existing = {
+  parent: exampleVNet
+  name: 'exampleSubnet'
+}
+
+resource exampleNic 'Microsoft.Network/networkInterfaces@2020-06-01' = {
+  name: 'exampleNic'
+  location: resourceGroup().location
+  dependsOn: [
+    exampleSubnet
+  ]
+  properties: {
+    ipConfigurations: [
+      {
+        name: 'ipconfig1'
+        properties: {
+          subnet: {
+            id: exampleSubnet.id
+          }
+        }
+      }
+    ]
+  }
+}
+----
+
+==== Compilant solution
+
+[source,bicep,diff-id=2,diff-type=compliant]
+----
+resource exampleVNet 'Microsoft.Network/virtualNetworks@2020-06-01' existing = {
+  name: 'exampleVNet'
+}
+
+resource exampleSubnet 'Microsoft.Network/virtualNetworks/subnets@2020-06-01' existing = {
+  parent: exampleVNet
+  name: 'exampleSubnet'
+}
+
+resource exampleNic 'Microsoft.Network/networkInterfaces@2020-06-01' = {
+  name: 'exampleNic'
+  location: resourceGroup().location
+  properties: {
+    ipConfigurations: [
+      {
+        name: 'ipconfig1'
+        properties: {
+          subnet: {
+            id: exampleSubnet.id
+          }
+        }
+      }
+    ]
+  }
+}
+----
+
+== Resources
+=== Documentation
+* https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/best-practices#resource-dependencies/[Azure Resource Manager templates best practices]
+* https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/resource-dependency#reference-and-list-functions[Azure Resource Manager - reference and list functions]
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+=== Message
+Remove this explicit dependency as it is already defined implicitly.
+
+Secondary location message: Implicit dependency is created via the "reference" function.
+
+=== Highlighting
+Highlight the redundant `dependsOn` element.
+
+endif::env-github,rspecator-view[]

rules/S6952/metadata.json

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+{
+}