ASP003 don't use nullable type when not optional. Close #35.

Author: JohanLarsson

AspNetCoreAnalyzers.Tests/ASP003ParameterTypeTests/CodeFix.cs

@@ -43,13 +43,13 @@ namespace ValidCode
     [ApiController]
     public class OrdersController : Controller
     {
-        [HttpGet(""api/orders/{id:int}"")]
+        [HttpGet(""api/orders/{id}"")]
         public IActionResult GetId(↓byte id)
         {
             return this.Ok(id);
         }
     }
-}".AssertReplace("\"api/orders/{id:int}\"", template);
+}".AssertReplace("\"api/orders/{id}\"", template);
 
             var fixedCode = @"
 namespace ValidCode
@@ -59,15 +59,55 @@ namespace ValidCode
     [ApiController]
     public class OrdersController : Controller
     {
-        [HttpGet(""api/orders/{id:int}"")]
+        [HttpGet(""api/orders/{id}"")]
         public IActionResult GetId(byte id)
         {
             return this.Ok(id);
         }
     }
-}".AssertReplace("\"api/orders/{id:int}\"", template)
+}".AssertReplace("\"api/orders/{id}\"", template)
   .AssertReplace("byte id", parameter);
             AnalyzerAssert.CodeFix(Analyzer, Fix, ExpectedDiagnostic, code, fixedCode);
         }
+
+        [TestCase("int?")]
+        [TestCase("Nullable<int>")]
+        public void WhenOptional(string parameter)
+        {
+            var code = @"
+namespace ValidCode
+{
+    using System;
+    using Microsoft.AspNetCore.Mvc;
+
+    [ApiController]
+    public class OrdersController : Controller
+    {
+        [HttpGet(""api/orders/{id}"")]
+        public IActionResult GetId(↓int? id)
+        {
+            return this.Ok(id);
+        }
+    }
+}".AssertReplace("int?", parameter);
+
+            var fixedCode = @"
+namespace ValidCode
+{
+    using System;
+    using Microsoft.AspNetCore.Mvc;
+
+    [ApiController]
+    public class OrdersController : Controller
+    {
+        [HttpGet(""api/orders/{id}"")]
+        public IActionResult GetId(int id)
+        {
+            return this.Ok(id);
+        }
+    }
+}";
+            AnalyzerAssert.CodeFix(Analyzer, Fix, ExpectedDiagnostic, code, fixedCode);
+        }
     }
 }

AspNetCoreAnalyzers/Analyzers/AttributeAnalyzer.cs

@@ -196,6 +196,15 @@ private static bool HasWrongType(ParameterPair pair, out string correctType)
                         return correctType != null;
                     }
                 }
+
+                if (!constraints.TryFirst(x => x.Span.Equals("?", StringComparison.Ordinal), out _) &&
+                    parameter.Type.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T &&
+                    parameter.Type is INamedTypeSymbol namedType &&
+                    namedType.TypeArguments.TrySingle(out var typeArg))
+                {
+                    correctType = typeArg.ToString();
+                    return true;
+                }
             }
 
             correctType = null;