Require nullable parameter type when route parameter is optional. Close #32

Author: JohanLarsson

AspNetCoreAnalyzers.Tests/ASP003ParameterSymbolTypeTests/CodeFix.cs

@@ -1,4 +1,4 @@
-namespace AspNetCoreAnalyzers.Tests.ASP003ParameterTypeTests
+namespace AspNetCoreAnalyzers.Tests.ASP003ParameterSymbolTypeTests
 {
     using Gu.Roslyn.Asserts;
     using Microsoft.CodeAnalysis.CodeFixes;
@@ -72,7 +72,7 @@ public IActionResult GetId(byte id)
 
         [TestCase("int?")]
         [TestCase("Nullable<int>")]
-        public void WhenNullableAndNotOptional(string parameter)
+        public void RemoveNullableWhenNotOptional(string parameter)
         {
             var code = @"
 namespace ValidCode
@@ -106,6 +106,45 @@ public IActionResult GetId(int id)
             return this.Ok(id);
         }
     }
+}";
+            AnalyzerAssert.CodeFix(Analyzer, Fix, ExpectedDiagnostic, code, fixedCode);
+        }
+
+        [Test]
+        public void MakeNullableToMatchOptional()
+        {
+            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);
+        }
+    }
+}";
+
+            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.Tests/ASP003ParameterSymbolTypeTests/ValidCode.cs

@@ -1,4 +1,4 @@
-namespace AspNetCoreAnalyzers.Tests.ASP003ParameterTypeTests
+namespace AspNetCoreAnalyzers.Tests.ASP003ParameterSymbolTypeTests
 {
     using Gu.Roslyn.Asserts;
     using Microsoft.CodeAnalysis.Diagnostics;

AspNetCoreAnalyzers/Analyzers/AttributeAnalyzer.cs

@@ -209,6 +209,16 @@ templateParameter.Constraints is ImmutableArray<RouteConstraint> constraints &&
                         correctConstraint = GetCorrectConstraintType(constraint);
                         return correctType != null;
                     }
+
+                    if (constraint.Span.Equals("?", StringComparison.Ordinal) &&
+                        parameterSymbol.Type.IsValueType &&
+                        parameterSymbol.Type.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T)
+                    {
+                        correctType = parameterSymbol.Type.ToDisplayString(SymbolDisplayFormat.MinimallyQualifiedFormat) + "?";
+                        constraintLocation = constraint.Span.GetLocation();
+                        correctConstraint = string.Empty;
+                        return true;
+                    }
                 }
 
                 if (!constraints.TryFirst(x => x.Span.Equals("?", StringComparison.Ordinal), out _) &&