riok · latonz · Oct 3, 2025 · Oct 3, 2025
diff --git a/src/Riok.Mapperly/Descriptors/InlineExpressionMappingBuilderContext.cs b/src/Riok.Mapperly/Descriptors/InlineExpressionMappingBuilderContext.cs
@@ -91,7 +91,7 @@ conversionType is not MappingConversionType.EnumToString and not MappingConversi
 
     public INewInstanceMapping? FindNewInstanceMapping(IMethodSymbol method)
     {
-        INewInstanceMapping? mapping = InlinedMappings.FindNewInstanceUserMapping(method, out var isInlined);
+        var mapping = InlinedMappings.FindNewInstanceMapping(method, out var isInlined);
         if (mapping == null)
             return null;
 

diff --git a/src/Riok.Mapperly/Descriptors/InlinedExpressionMappingCollection.cs b/src/Riok.Mapperly/Descriptors/InlinedExpressionMappingCollection.cs
@@ -44,7 +44,7 @@ public class InlinedExpressionMappingCollection
         return _delegate.FindNewInstanceMapping(mappingKey);
     }
 
-    public INewInstanceUserMapping? FindNewInstanceUserMapping(IMethodSymbol method, out bool isInlined)
+    public INewInstanceMapping? FindNewInstanceMapping(IMethodSymbol method, out bool isInlined)
     {
         var mapping = _delegate.FindNewInstanceUserMapping(method);
         if (mapping == null)
@@ -56,7 +56,7 @@ public class InlinedExpressionMappingCollection
         if (_inlinedMappings.TryGetValue(new TypeMappingKey(mapping), out var inlinedMapping))
         {
             isInlined = true;
-            return inlinedMapping as INewInstanceUserMapping;
+            return inlinedMapping;
         }
 
         isInlined = false;

diff --git a/test/Riok.Mapperly.Tests/Mapping/QueryableProjectionUserImplementedTest.cs b/test/Riok.Mapperly.Tests/Mapping/QueryableProjectionUserImplementedTest.cs
@@ -292,4 +292,109 @@ public Task UserImplementedAttributedNullableValueTypeToNullableMemberTypeMismat
 
         return TestHelper.VerifyGenerator(source);
     }
+
+    [Fact]
+    public Task UserImplementedTwoNestedProjectionsShouldReuseInlinedMapping()
+    {
+        // https://github.com/riok/mapperly/issues/1965
+        var source = TestSourceBuilder.CSharp(
+            """
+            using System;
+            using System.Collections.Generic;
+            using Riok.Mapperly.Abstractions;
+            using System.Linq;
+
+            [Mapper]
+            public static partial class Mapper
+            {
+                public static partial IQueryable<VendorResponse> ProjectToDto(this IQueryable<Vendor> query);
+                public static partial IQueryable<ScopeResponse> ProjectToDto(this IQueryable<Scope> q);
+
+                [MapPropertyFromSource(nameof(CountryListResponse.Name), Use = nameof(GetCountryLocalizedName))]
+                public static partial CountryListResponse ToCountryListDto(this Country q);
+
+                private static IReadOnlyCollection<CountryListResponse> MapScopeCountries(ICollection<ScopeCountry> countries)
+                {
+                    return countries.Select(c => ToCountryListDto(c.Country)).ToList();
+                }
+
+                private static IReadOnlyCollection<CountryListResponse> MapVendorCountries(ICollection<VendorCountry> models)
+                {
+                    return models.Select(x => ToCountryListDto(x.Country)).ToList();
+                }
+
+                private static string GetCountryLocalizedName(Country x)
+                {
+                    return x.LocalizedNames.FirstOrDefault()!.Name ?? x.Name;
+                }
+            }
+
+            public class Vendor
+            {
+                public string VendorName { get; set; } = null!;
+                public ICollection<VendorCountry> Countries { get; set; } = [];
+            }
+
+            public class VendorCountry
+            {
+                public Guid VendorId { get; set; }
+                public Vendor Vendor { get; set; } = null!;
+                public Guid CountryId { get; set; }
+                public Country Country { get; set; } = null!;
+            }
+
+            public class Scope
+            {
+                public Guid Id { get; set; }
+                public ICollection<ScopeCountry> Countries { get; set; } = [];
+            }
+
+            public class ScopeCountry
+            {
+                public Guid ScopeId { get; set; }
+                public Scope Scope { get; set; } = null!;
+                public Guid CountryId { get; set; }
+                public Country Country { get; set; } = null!;
+            }
+
+            public class Country
+            {
+                public string Code { get; set; } = null!;
+                public string Name { get; set; } = null!;
+                public ICollection<LocalizedName> LocalizedNames { get; set; } = [];
+            }
+
+            public class LocalizedName
+            {
+                public string LanguageCode { get; set; } = null!;
+                public string Name { get; set; } = null!;
+            }
+
+            public class CountryListResponse
+            {
+                public required string Code { get; set; }
+                public required string Name { get; set; }
+            }
+
+            public class CountryListResponse2
+            {
+                public required string Code { get; set; }
+                public required string Name { get; set; }
+            }
+
+            public class VendorResponse
+            {
+                public required string VendorName { get; set; }
+                public IReadOnlyCollection<CountryListResponse> Countries { get; set; } = [];
+            }
+
+            public class ScopeResponse
+            {
+                public required Guid Id { get; set; }
+                public IReadOnlyCollection<CountryListResponse> Countries { get; set; } = [];
+            }
+            """
+        );
+        return TestHelper.VerifyGenerator(source);
+    }
 }
diff --git a/...tedTest.UserImplementedTwoNestedProjectionsShouldReuseInlinedMapping#Mapper.g.verified.cs b/...tedTest.UserImplementedTwoNestedProjectionsShouldReuseInlinedMapping#Mapper.g.verified.cs
@@ -0,0 +1,54 @@
+//HintName: Mapper.g.cs
+// <auto-generated />
+#nullable enable
+public static partial class Mapper
+{
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public static partial global::System.Linq.IQueryable<global::VendorResponse> ProjectToDto(this global::System.Linq.IQueryable<global::Vendor> query)
+    {
+#nullable disable
+        return global::System.Linq.Queryable.Select(
+            query,
+            x => new global::VendorResponse()
+            {
+                VendorName = x.VendorName,
+                Countries = global::System.Linq.Enumerable.ToList(global::System.Linq.Enumerable.Select(x.Countries, x => new global::CountryListResponse()
+                {
+                    Code = x.Country.Code,
+                    Name = global::System.Linq.Enumerable.FirstOrDefault(x.Country.LocalizedNames)!.Name ?? x.Country.Name,
+                })),
+            }
+        );
+#nullable enable
+    }
+
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public static partial global::System.Linq.IQueryable<global::ScopeResponse> ProjectToDto(this global::System.Linq.IQueryable<global::Scope> q)
+    {
+#nullable disable
+        return global::System.Linq.Queryable.Select(
+            q,
+            x => new global::ScopeResponse()
+            {
+                Id = x.Id,
+                Countries = global::System.Linq.Enumerable.ToList(global::System.Linq.Enumerable.Select(x.Countries, c => new global::CountryListResponse()
+                {
+                    Code = c.Country.Code,
+                    Name = global::System.Linq.Enumerable.FirstOrDefault(c.Country.LocalizedNames)!.Name ?? c.Country.Name,
+                })),
+            }
+        );
+#nullable enable
+    }
+
+    [global::System.CodeDom.Compiler.GeneratedCode("Riok.Mapperly", "0.0.1.0")]
+    public static partial global::CountryListResponse ToCountryListDto(this global::Country q)
+    {
+        var target = new global::CountryListResponse()
+        {
+            Code = q.Code,
+            Name = GetCountryLocalizedName(q),
+        };
+        return target;
+    }
+}
diff --git a/...plementedTest.UserImplementedTwoProjectionsShouldReuseInlinedMapping#Mapper.g.verified.cs b/...plementedTest.UserImplementedTwoProjectionsShouldReuseInlinedMapping#Mapper.g.verified.cs
diff --git a/...onUserImplementedTest.UserImplementedTwoProjectionsShouldReuseInlinedMapping.verified.txt b/...onUserImplementedTest.UserImplementedTwoProjectionsShouldReuseInlinedMapping.verified.txt
diff --git a/test/Riok.Mapperly.Tests/_snapshots/UseMapperTest.UseMapper.verified.txt b/test/Riok.Mapperly.Tests/_snapshots/UseMapperTest.UseMapper.verified.txt