fix: correctly annotate nullable generics in disabled nullable contex…

…ts (#1020)

src/Riok.Mapperly/Helpers/NullableSymbolExtensions.cs

@@ -1,3 +1,4 @@
+using System.Collections.Immutable;
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis;
 
@@ -38,7 +39,7 @@ internal static bool TryUpgradeNullable(this ITypeSymbol symbol, [NotNullWhen(tr
             return false;
         }
 
-        upgradedSymbol = symbol.WithNullableAnnotation(NullableAnnotation.Annotated);
+        upgradedSymbol = symbol.WithDeepNullableAnnotation(NullableAnnotation.Annotated);
         return true;
     }
 
@@ -112,4 +113,24 @@ internal static bool IsNullable(this ITypeParameterSymbol typeParameter, Nullabl
 
     internal static bool IsNullable(this NullableAnnotation nullable) =>
         nullable is NullableAnnotation.Annotated or NullableAnnotation.None;
+
+    /// <summary>
+    /// Returns a new type symbol with the provided nullable annotation.
+    /// Also sets the nullable annotation on all type arguments of the <see cref="symbol"/>.
+    /// </summary>
+    /// <param name="symbol">The symbol to work on.</param>
+    /// <param name="annotation">The <see cref="NullableAnnotation"/> to set.</param>
+    /// <returns>The new symbol with the given nullable annotation.</returns>
+    private static ITypeSymbol WithDeepNullableAnnotation(this ITypeSymbol symbol, NullableAnnotation annotation)
+    {
+        if (symbol is INamedTypeSymbol { TypeArguments.Length: > 0 } namedSymbol)
+        {
+            symbol = namedSymbol.ConstructedFrom.Construct(
+                namedSymbol.TypeArguments,
+                Enumerable.Repeat(annotation, namedSymbol.TypeArguments.Length).ToImmutableArray()
+            );
+        }
+
+        return symbol.WithNullableAnnotation(annotation);
+    }
 }

test/Riok.Mapperly.Tests/Mapping/EnumerableTest.cs

@@ -550,6 +550,14 @@ public Task ArrayToReadOnlyCollectionShouldUpgradeNullability()
         return TestHelper.VerifyGenerator(source, TestHelperOptions.DisabledNullable);
     }
 
+    [Fact]
+    public Task ShouldUpgradeNullabilityOfGenericInDisabledNullableContext()
+    {
+        var source = TestSourceBuilder.Mapping("IList<A>", "IList<B>", "record A(int V);", "record B(int V);");
+
+        return TestHelper.VerifyGenerator(source, TestHelperOptions.DisabledNullable);
+    }
+
     [Fact]
     public Task ArrayToCollectionShouldUpgradeNullability()
     {

test/Riok.Mapperly.Tests/_snapshots/EnumerableTest.ShouldUpgradeNullabilityOfGenericInDisabledNullableContext#Mapper.g.verified.cs

@@ -0,0 +1,25 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public partial class Mapper
+{
+    private partial global::System.Collections.Generic.IList<global::B?>? Map(global::System.Collections.Generic.IList<global::A?>? source)
+    {
+        if (source == null)
+            return default;
+        var target = new global::System.Collections.Generic.List<global::B?>(source.Count);
+        foreach (var item in source)
+        {
+            target.Add(MapToB(item));
+        }
+        return target;
+    }
+
+    private global::B? MapToB(global::A? source)
+    {
+        if (source == null)
+            return default;
+        var target = new global::B(source.V);
+        return target;
+    }
+}