fix: initialize nullable values when assigning null to a child member

riok · Aug 8, 2024 · 6649fb8 · 6649fb8
1 parent 0870816
commit 6649fb8
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Showing 2 changed files with 53 additions and 4 deletions.
diff --git a/...Mapperly/Descriptors/MappingBodyBuilders/BuilderContext/MembersContainerBuilderContext.cs b/...Mapperly/Descriptors/MappingBodyBuilders/BuilderContext/MembersContainerBuilderContext.cs
@@ -32,6 +32,23 @@ public void AddNullDelegateMemberAssignmentMapping(IMemberAssignmentMapping memb
             return;
         }
 
+        // set target member to null if null assignments are allowed
+        // and the source is null
+        var setMemberToNull =
+            BuilderContext.Configuration.Mapper.AllowNullPropertyAssignment
+            && memberMapping.MemberInfo.TargetMember.Member.Type.IsNullable();
+
+        // if the member is explicitly set to null,
+        // make sure the parent members are initialized/non-null,
+        // no matter of the null conditional source-path.
+        // otherwise this initialization would only happen
+        // if the source member is not null,
+        // and the null assignment in the else case could fail if the target parent member is not initialized.
+        if (setMemberToNull)
+        {
+            AddNullMemberInitializers(Mapping, memberMapping.MemberInfo.TargetMember);
+        }
+
         var nullConditionSourcePath = new NonEmptyMemberPath(
             memberMapping.MemberInfo.SourceMember.MemberPath.RootType,
             memberMapping.MemberInfo.SourceMember.MemberPath.PathWithoutTrailingNonNullable().ToList()
@@ -41,10 +58,7 @@ public void AddNullDelegateMemberAssignmentMapping(IMemberAssignmentMapping memb
 
         // set target member to null if null assignments are allowed
         // and the source is null
-        if (
-            BuilderContext.Configuration.Mapper.AllowNullPropertyAssignment
-            && memberMapping.MemberInfo.TargetMember.Member.Type.IsNullable()
-        )
+        if (setMemberToNull)
         {
             var targetMemberSetter = memberMapping.MemberInfo.TargetMember.BuildSetter(BuilderContext);
             container.AddNullMemberAssignment(targetMemberSetter);

diff --git a/test/Riok.Mapperly.Tests/Mapping/ObjectPropertyNullableTest.cs b/test/Riok.Mapperly.Tests/Mapping/ObjectPropertyNullableTest.cs
@@ -518,6 +518,41 @@ TestSourceBuilderOptions.Default with
             );
     }
 
+    [Fact]
+    public void NullableNestedMembersShouldInitialize()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            """
+            [MapProperty("Value", "SubValue.Value")]
+            public partial B Map(A a)
+            """,
+            "class A { public C? Value { get; set; } }",
+            "class B { public D? SubValue { get; set; } }",
+            "class C { public int V { get; set; } }",
+            "class D { public E? Value { get; set; } }",
+            "class E { public int V { get; set; } }"
+        );
+
+        TestHelper
+            .GenerateMapper(source)
+            .Should()
+            .HaveMapMethodBody(
+                """
+                var target = new global::B();
+                target.SubValue ??= new global::D();
+                if (a.Value != null)
+                {
+                    target.SubValue.Value = MapToE(a.Value);
+                }
+                else
+                {
+                    target.SubValue.Value = null;
+                }
+                return target;
+                """
+            );
+    }
+
     [Fact]
     public void NullableClassToNullableClassPropertyThrowShouldSetNull()
     {