fix: allow same-name members with different casings (#1350)

src/Riok.Mapperly/Descriptors/MappingBodyBuilders/BuilderContext/MembersMappingStateBuilder.cs

@@ -30,7 +30,9 @@ public static MembersMappingState Build(MappingBuilderContext ctx)
         unmappedSourceMemberNames.ExceptWith(ignoredSourceMemberNames);
         targetMembers.RemoveRange(ignoredTargetMemberNames);
 
-        var targetMemberCaseMapping = targetMembers.Keys.ToDictionary(x => x, x => x, StringComparer.OrdinalIgnoreCase);
+        var targetMemberCaseMapping = targetMembers
+            .Keys.GroupBy(x => x, StringComparer.OrdinalIgnoreCase)
+            .ToDictionary(x => x.Key, x => x.First(), StringComparer.OrdinalIgnoreCase);
         var unmappedTargetMemberNames = targetMembers.Keys.ToHashSet();
         return new MembersMappingState(
             unmappedSourceMemberNames,

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

@@ -435,6 +435,35 @@ public void UnmappedReadOnlyTargetPropertyShouldNotDiagnostic()
             );
     }
 
+    [Fact]
+    public Task PropertiesWithCaseInsensitiveEqualNamesShouldWork()
+    {
+        var source = TestSourceBuilder.Mapping(
+            "A",
+            "B",
+            "class A { public int Value { get; set; } }",
+            "class B { public int value { get; set; } public int Value { get; set; } }"
+        );
+
+        return TestHelper.VerifyGenerator(source);
+    }
+
+    [Fact]
+    public Task PropertyConfigurationShouldPreferExactCasing()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            """
+            [MapProperty("Value", "value")]
+            [MapProperty("value", "Value")]
+            public partial B Map(A source);
+            """,
+            "class A { public int value { get; set; } public int Value { get; set; } }",
+            "class B { public int value { get; set; } public int Value { get; set; } }"
+        );
+
+        return TestHelper.VerifyGenerator(source);
+    }
+
     [Fact]
     public void ShouldIgnoreStaticProperty()
     {

test/Riok.Mapperly.Tests/_snapshots/ObjectPropertyTest.PropertiesWithCaseInsensitiveEqualNamesShouldWork#Mapper.g.verified.cs

@@ -0,0 +1,13 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public partial class Mapper
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    private partial global::B Map(global::A source)
+    {
+        var target = new global::B();
+        target.Value = source.Value;
+        return target;
+    }
+}

test/Riok.Mapperly.Tests/_snapshots/ObjectPropertyTest.PropertiesWithCaseInsensitiveEqualNamesShouldWork.verified.txt

@@ -0,0 +1,14 @@
+{
+  Diagnostics: [
+    {
+      Id: RMG012,
+      Title: Source member was not found for target member,
+      Severity: Info,
+      WarningLevel: 1,
+      Location: : (11,4)-(11,36),
+      MessageFormat: The member {0} on the mapping target type {1} was not found on the mapping source type {2},
+      Message: The member value on the mapping target type B was not found on the mapping source type A,
+      Category: Mapper
+    }
+  ]
+}

test/Riok.Mapperly.Tests/_snapshots/ObjectPropertyTest.PropertyConfigurationShouldPreferExactCasing#Mapper.g.verified.cs

@@ -0,0 +1,14 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public partial class Mapper
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public partial global::B Map(global::A source)
+    {
+        var target = new global::B();
+        target.value = source.Value;
+        target.Value = source.value;
+        return target;
+    }
+}