fix: do not resolve existing one sideded loose nullable property mapp…

…ings (#1090)

src/Riok.Mapperly/Descriptors/MappingBuilderContext.cs

@@ -139,9 +139,7 @@ bool clearDerivedTypes
     /// Finds or builds a mapping (<seealso cref="FindOrBuildMapping(Riok.Mapperly.Descriptors.TypeMappingKey,Riok.Mapperly.Descriptors.MappingBuildingOptions,Location)"/>).
     /// Before a new mapping is built existing mappings are tried to be found by the following priorities:
     /// 1. exact match
-    /// 2. ignoring the nullability of the source (needs to be handled by the caller of this method)
-    /// 3. ignoring the nullability of the target (needs to be handled by the caller of this method)
-    /// 4. ignoring the nullability of the source and the target (needs to be handled by the caller of this method)
+    /// 2. ignoring the nullability of the source and the target (needs to be handled by the caller of this method)
     /// If no mapping can be found a new mapping is built with the source and the target as non-nullables.
     /// </summary>
     /// <param name="key">The mapping key.</param>
@@ -154,10 +152,7 @@ bool clearDerivedTypes
         Location? diagnosticLocation = null
     )
     {
-        return FindMapping(key)
-            ?? FindMapping(key.NonNullableSource())
-            ?? FindMapping(key.NonNullableTarget())
-            ?? FindOrBuildMapping(key.NonNullable(), options, diagnosticLocation);
+        return FindMapping(key) ?? FindOrBuildMapping(key.NonNullable(), options, diagnosticLocation);
     }
 
     /// <summary>

src/Riok.Mapperly/Descriptors/TypeMappingKey.cs

@@ -24,10 +24,6 @@ public TypeMappingKey(ITypeMapping mapping, TypeMappingConfiguration? config = n
 
     public TypeMappingConfiguration Configuration { get; } = config ?? TypeMappingConfiguration.Default;
 
-    public TypeMappingKey NonNullableSource() => new(Source.NonNullable(), Target, Configuration);
-
-    public TypeMappingKey NonNullableTarget() => new(Source, Target.NonNullable(), Configuration);
-
     public TypeMappingKey NonNullable() => new(Source.NonNullable(), Target.NonNullable(), Configuration);
 
     private bool Equals(TypeMappingKey other) =>

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

@@ -730,4 +730,22 @@ public void NullableDirectiveEnabledTargetWithSameNullableRefTypeAsPropertyAndIn
                 """
             );
     }
+
+    [Fact]
+    public Task NullableToNullablePropertyWithAnotherNullableToNonNullableMappingShouldDirectAssign()
+    {
+        // see https://github.com/riok/mapperly/issues/1089
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            """
+            public static partial ADest? Map(A? source);
+            public static partial BDest MapToDestinationB(B source);
+            """,
+            "public record A(int? Prop);",
+            "public record B(List<int?> Prop);",
+            "public record ADest(int? Prop);",
+            "public record BDest(List<int> Prop);"
+        );
+
+        return TestHelper.VerifyGenerator(source);
+    }
 }

test/Riok.Mapperly.Tests/_snapshots/ObjectPropertyNullableTest.NullableToNullablePropertyWithAnotherNullableToNonNullableMappingShouldDirectAssign#Mapper.g.verified.cs

@@ -0,0 +1,32 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public partial class Mapper
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public static partial global::ADest? Map(global::A? source)
+    {
+        if (source == null)
+            return default;
+        var target = new global::ADest(source.Prop);
+        return target;
+    }
+
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public static partial global::BDest MapToDestinationB(global::B source)
+    {
+        var target = new global::BDest(MapToList(source.Prop));
+        return target;
+    }
+
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    private static global::System.Collections.Generic.List<int> MapToList(global::System.Collections.Generic.IReadOnlyCollection<int?> source)
+    {
+        var target = new global::System.Collections.Generic.List<int>(source.Count);
+        foreach (var item in source)
+        {
+            target.Add(item == null ? throw new System.ArgumentNullException(nameof(item)) : item.Value);
+        }
+        return target;
+    }
+}