Support nullable parameters

src/Jab.FunctionalTests.Common/ConstructorSelectionTests.cs

@@ -59,6 +59,7 @@ public void PassesOptionalParametersWhenAvailable()
             Assert.NotNull(service.Parameter1);
             Assert.Null(service.Parameter2);
             Assert.NotNull(service.Parameter3);
+            Assert.False(typeof(IServiceProvider<IService2>).IsAssignableFrom(typeof(PassesOptionalParametersWhenAvailableContainer)));
         }
 
         [ServiceProvider]
@@ -83,5 +84,21 @@ public void IgnoresNonReferenceTypedParameters()
         [Transient(typeof(IService3), typeof(ServiceImplementation))]
         [Transient(typeof(IService), typeof(ServiceImplementationWithParameter<IService1, int, IService3>))]
         internal partial class IgnoresNonReferenceTypedParametersContainer { }
+
+        [Fact]
+        public void IgnoresNullableOptionalParametersWhenNotAvailable()
+        {
+            IgnoresNullableOptionalParametersWhenNotAvailableContainer c = new();
+            var service = Assert.IsType<ServiceImplementationWithNullableOptional>(c.GetService<IService>());
+            Assert.NotNull(service.Parameter1);
+            Assert.Null(service.Parameter2);
+            Assert.Empty(service.Parameter3!);
+            Assert.False(typeof(IServiceProvider<IService2>).IsAssignableFrom(typeof(IgnoresNullableOptionalParametersWhenNotAvailableContainer)));
+        }
+
+        [ServiceProvider]
+        [Transient(typeof(IService1), typeof(ServiceImplementation))]
+        [Transient(typeof(IService), typeof(ServiceImplementationWithNullableOptional))]
+        internal partial class IgnoresNullableOptionalParametersWhenNotAvailableContainer { }
     }
 }

src/Jab.FunctionalTests.Common/Mocks/ServiceImplementationWithNullableOptional.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+
+namespace JabTests;
+
+#nullable enable
+
+internal class ServiceImplementationWithNullableOptional : IService
+{
+    public IService1 Parameter1 { get; }
+    public IService2? Parameter2 { get; }
+    public IEnumerable<IService3>? Parameter3 { get; }
+
+    public ServiceImplementationWithNullableOptional(
+        IService1 parameter1,
+        IService2? parameter2 = null,
+        IEnumerable<IService3>? parameter3 = null)
+    {
+        Parameter1 = parameter1;
+        Parameter2 = parameter2;
+        Parameter3 = parameter3;
+    }
+}

src/Jab.Tests/DiagnosticsTest.cs

@@ -1,4 +1,5 @@
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Testing;
 using Xunit;
 using Verify = JabTests.GeneratorAnalyzerVerifier<Jab.ContainerGenerator>;
@@ -279,5 +280,45 @@ await Verify.VerifyAnalyzerAsync(testCode,
                     .WithLocation(1)
                     .WithArguments("IService"));
         }
+
+        [Fact]
+        public async Task ProducesJAB0013WhenNullableNonOptionalDependencyNotFound()
+        {
+            string testCode = $@"
+#nullable enable
+interface IDependency {{ }}
+class Service {{ public Service(IDependency? dep) {{}} }}
+[ServiceProvider]
+[{{|#1:Transient(typeof(Service))|}}]
+public partial class Container {{}}
+";
+            await Verify.VerifyAnalyzerAsync(testCode,
+                DiagnosticResult
+                    .CompilerError("JAB0013")
+                    .WithSeverity(DiagnosticSeverity.Error)
+                    .WithLocation(1)
+                    .WithArguments("IDependency?", "Service"));
+        }
+
+        [Fact]
+        public async Task ProducesJAB0014WhenNullableNonOptionalDependencyFound()
+        {
+            string testCode = $@"
+#nullable enable
+interface IDependency {{ }}
+class Dependency : IDependency {{ }}
+class Service {{ public Service(IDependency? dep) {{}} }}
+[ServiceProvider]
+[{{|#1:Transient(typeof(Service))|}}]
+[{{|#2:Transient(typeof(IDependency), typeof(Dependency))|}}]
+public partial class Container {{}}
+";
+            await Verify.VerifyAnalyzerAsync(testCode,
+                DiagnosticResult
+                    .CompilerError("JAB0014")
+                    .WithSeverity(DiagnosticSeverity.Warning)
+                    .WithLocation(1)
+                    .WithArguments("IDependency?", "Service"));
+        }
     }
 }

src/Jab/CodeWriter.cs

@@ -170,7 +170,7 @@ private void AppendType(INamedTypeSymbol namedTypeSymbol)
     {
         if (!_typeNameCache.TryGetValue(namedTypeSymbol, out var name))
         {
-            name = _typeNameCache[namedTypeSymbol] = namedTypeSymbol.ToDisplayString();
+            name = _typeNameCache[namedTypeSymbol] = namedTypeSymbol.ToDisplayString(NullableFlowState.NotNull);
         }
 
         AppendRaw(name);

src/Jab/ContainerGenerator.cs

@@ -589,6 +589,8 @@ public override void Initialize(AnalysisContext context)
         DiagnosticDescriptors.NoServiceTypeRegistered,
         DiagnosticDescriptors.ImplementationTypeAndFactoryNotAllowed,
         DiagnosticDescriptors.FactoryMemberMustBeAMethodOrHaveDelegateType,
+        DiagnosticDescriptors.NullableServiceNotRegistered,
+        DiagnosticDescriptors.NullableServiceRegistered,
     }.ToImmutableArray();
 
     private static string ReadAttributesFile()

src/Jab/DiagnosticDescriptors.cs

@@ -50,4 +50,12 @@ internal static class DiagnosticDescriptors
         "The factory member has to be a method or have a delegate type",
         "The factory member '{0}' has to be a method of have a delegate type, for service '{1}'", "Usage", DiagnosticSeverity.Error, true);
 
+    public static readonly DiagnosticDescriptor NullableServiceNotRegistered = new("JAB0013",
+        "Not registered nullable dependency without a default value",
+        "The nullable service '{0}' requested to construct '{1}' is not registered. Add a default value to make the service reference optional", "Usage", DiagnosticSeverity.Error, true);
+
+    public static readonly DiagnosticDescriptor NullableServiceRegistered = new("JAB0014",
+        "Nullable dependency without a default value",
+        "'{0}' parameter to construct '{1}' will never be null when constructing using a service provider. Add a default value to make the service reference optional", "Usage", DiagnosticSeverity.Warning, true);
+
 }

src/Jab/ServiceProviderBuilder.cs

@@ -690,9 +690,11 @@ private ServiceCallSite CreateConstructorCallSite(
             }
             else
             {
+                bool isNullable = parameterSymbol.Type.NullableAnnotation == NullableAnnotation.Annotated;
                 if (parameterCallSite == null)
                 {
-                    var diagnostic = Diagnostic.Create(DiagnosticDescriptors.ServiceRequiredToConstructNotRegistered,
+                    var diagnostic = Diagnostic.Create(
+                        isNullable ? DiagnosticDescriptors.NullableServiceNotRegistered : DiagnosticDescriptors.ServiceRequiredToConstructNotRegistered,
                         registrationLocation,
                         parameterSymbol.Type.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat),
                         implementationType.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat));
@@ -702,6 +704,17 @@ private ServiceCallSite CreateConstructorCallSite(
                 }
                 else
                 {
+                    if (isNullable)
+                    {
+                        var diagnostic = Diagnostic.Create(
+                                DiagnosticDescriptors.NullableServiceRegistered,
+                                registrationLocation,
+                                parameterSymbol.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat),
+                                implementationType.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat));
+
+                        _context.ReportDiagnostic(diagnostic);
+                    }
+
                     callSites.Add(parameterCallSite);
                 }
             }