Create rule S6961: API Controllers should derive from ControllerBase instead of Controller (#3846)

rules/S6961/csharp/metadata.json

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+{
+  "title": "API Controllers should derive from ControllerBase instead of Controller",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "asp.net",
+    "performance"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-6961",
+  "sqKey": "S6961",
+  "scope": "Main",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "targeted",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "MEDIUM"
+    },
+    "attribute": "COMPLETE"
+  }
+}

rules/S6961/csharp/rule.adoc

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+In https://learn.microsoft.com/en-us/aspnet/core[ASP.NET Core], controllers usually inherit either from https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.controllerbase[`ControllerBase`] or https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.controller[`Controller`]. If a controller does not use any View-specific functionality, it is recommended to inherit from `ControllerBase`.
+
+== Why is this an issue?
+
+The `ControllerBase` class contains all the necessary functionality to handle https://en.wikipedia.org/wiki/Web_API[API] requests and responses. The `Controller` class inherits from `ControllerBase` and adds support for https://learn.microsoft.com/en-us/aspnet/core/mvc/views/overview[Views], https://learn.microsoft.com/en-us/aspnet/core/mvc/views/partial[PartialViews] and https://learn.microsoft.com/en-us/aspnet/core/mvc/views/view-components[ViewComponents].
+
+Inheriting from `Controller` when not using any View-specific functionality exposes unnecessary methods and can lead to confusion about the intention of the class.
+
+Furthermore, inheriting from `Controller` may come with a performance cost. Even though the controller might only deal with API operations, the support for Views might introduce some overhead from the MVC framework during the https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware[request processing pipeline].
+
+An issue is raised when:
+
+* The class is marked with the https://learn.microsoft.com/en-us/aspnet/core/web-api#apicontroller-attribute[`++[ApiController]++`] attribute.
+* The class inherits _directly_ from `Controller`.
+* No View-specific functionality is used in the class.
+
+=== Exceptions
+
+* If a class is marked with the https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.noncontrollerattribute[`++[NonController]++`] attribute.
+* If a class does not have https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/public[public] accessibility.
+
+
+== How to fix it
+
+Change the base type of the controller from `Controller` to `ControllerBase`.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,csharp,diff-id=1,diff-type=noncompliant]
+----
+[ApiController]
+public class MyController : Controller // Noncompliant: Inherit from ControllerBase instead of Controller.
+//                          ^^^^^^^^^^
+{
+    // ..
+}
+----
+
+==== Compliant solution
+
+[source,csharp,diff-id=1,diff-type=compliant]
+----
+[ApiController]
+public class MyController : ControllerBase
+{
+    // ..
+}
+----
+
+== Resources
+
+=== Documentation
+
+* Wikipedia - https://en.wikipedia.org/wiki/Web_API[Web API]
+* Microsoft Learn - https://learn.microsoft.com/en-us/aspnet/core[ASP.NET Core]
+* Microsoft Learn - https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.controller[Controller Class]
+* Microsoft Learn - https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.controllerbase[ControllerBase Class]
+* Microsoft Learn - https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.apicontrollerattribute[ApiControllerAttribute Class]
+* Microsoft Learn - https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.noncontrollerattribute[NonControllerAttribute Class]
+* Microsoft Learn - https://learn.microsoft.com/en-us/aspnet/core/mvc/views/overview[Views in ASP.NET Core MVC]
+* Microsoft Learn - https://learn.microsoft.com/en-us/aspnet/core/mvc/views/partial[Partial Views in ASP.NET Core MVC]
+* Microsoft Learn - https://learn.microsoft.com/en-us/aspnet/core/mvc/views/view-components[View Components in ASP.NET Core MVC]
+* Microsoft Learn - https://learn.microsoft.com/en-us/aspnet/core/fundamentals/middleware[ASP.NET Core Middleware]
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+=== Message
+
+* Inherit from ControllerBase instead of Controller.
+
+=== Highlighting
+
+The `Controller` base type of the class declaration.
+
+'''
+== Comments And Links
+(visible only on this page)
+
+endif::env-github,rspecator-view[]

rules/S6961/metadata.json

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+{
+}