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fix: forward wrapped access of hidden interface members to the declaring interface #848

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fix: forward wrapped access of hidden interface members to the declaring interface #848

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372528a
fix: forward wrapped access of hidden interface members to the declar…
vbreuss Aug 25, 2026
00aff0c
fix: do not forward init-only class properties to the wrapped instance
vbreuss Aug 25, 2026
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3 changes: 3 additions & 0 deletions Docs/pages/01-create-mocks.md
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,9 @@ wrappedDispenser.Mock.Verify.Dispense(It.Is("Dark"), It.Is(5)).Once();

- Both interface and class types can be wrapped.
- All public calls are forwarded to the wrapped instance.
- Members that hide a base member with `new` are forwarded to the interface that declares them, so each
interface view of the mock reaches the matching member on the wrapped instance.
- You can still set up custom behavior that overrides the wrapped instance's behavior.
- Protected members are not forwarded to the wrapped instance; the base class implementation is used instead.
- Init-only properties are not forwarded to the wrapped instance, since it is already constructed.
- Verification works the same as with regular mocks.
40 changes: 24 additions & 16 deletions Source/Mockolate.SourceGenerators/Sources/Sources.MockClass.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1592,8 +1592,12 @@ private static void AppendMockSubject_ImplementClass_AddEvent(StringBuilder sb,
}

sb.AppendLine("\t\t{");
bool supportsWrapping = @event is { IsStatic: false, IsProtected: false, ExplicitImplementation: null, } &&
bool supportsWrapping = @event is { IsStatic: false, IsProtected: false, } &&
!explicitInterfaceImplementation;
// An event that hides a base member (`new`) is emitted as an explicit interface implementation.
// The wrapped instance must be cast to the declaring interface, otherwise the subscription
// binds to the hiding member, whose delegate type differs from the one being implemented.
string wrapsType = @event.ExplicitImplementation ?? className;
bool supportsBaseForwarding = supportsWrapping && !isClassInterface && @event.UseOverride && !@event.IsAbstract;
if (supportsWrapping)
{
Expand All @@ -1604,7 +1608,7 @@ private static void AppendMockSubject_ImplementClass_AddEvent(StringBuilder sb,
sb.Append("\t\t\t\t\t").Append(mockRegistry).Append(addCall).Append(@event.GetUniqueNameString()).Append(", value.Target, value.Method);").AppendLine();
sb.Append("\t\t\t\t}").AppendLine();
sb.Append("\t\t\t\t").Append(backingFieldAccess).Append(" += value;").AppendLine();
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(className).Append(" wraps)").AppendLine();
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType).Append(" wraps)").AppendLine();
sb.Append("\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\twraps.").Append(@event.Name).Append(" += value;").AppendLine();
sb.Append("\t\t\t\t}").AppendLine();
Expand All @@ -1624,7 +1628,7 @@ private static void AppendMockSubject_ImplementClass_AddEvent(StringBuilder sb,
sb.Append("\t\t\t\t\t").Append(mockRegistry).Append(removeCall).Append(@event.GetUniqueNameString()).Append(", value.Target, value.Method);").AppendLine();
sb.Append("\t\t\t\t}").AppendLine();
sb.Append("\t\t\t\t").Append(backingFieldAccess).Append(" -= value;").AppendLine();
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(className).Append(" wraps)").AppendLine();
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType).Append(" wraps)").AppendLine();
sb.Append("\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\twraps.").Append(@event.Name).Append(" -= value;").AppendLine();
sb.Append("\t\t\t\t}").AppendLine();
Expand Down Expand Up @@ -1669,6 +1673,10 @@ private static void AppendMockSubject_ImplementClass_AddProperty(StringBuilder s
#pragma warning restore S107
{
string mockRegistry = property.IsStatic ? "MockRegistryProvider.Value" : $"this.{mockRegistryName}";
// A property that hides a base member (`new`) is emitted as an explicit interface implementation.
// The wrapped instance must be cast to the declaring interface, otherwise the delegated access
// binds to the hiding member instead: wrong property type (CS0266).
string wrapsType = property.ExplicitImplementation ?? className;
bool useFastForProperty = useFastBuffers && !property.IsIndexer && IsFastBufferEligibleProperty(property);
bool useFastForIndexer = useFastBuffers && property.IsIndexer && IsFastBufferEligibleIndexer(property);
string indexerGetIdRef = property.IsIndexer
Expand Down Expand Up @@ -1764,7 +1772,7 @@ property.IndexerParameters is not null
{
AppendRefStructIndexerGetterBody(sb, property, mockRegistry);
}
else if (isClassInterface && !explicitInterfaceImplementation && property.ExplicitImplementation is null)
else if (isClassInterface && !explicitInterfaceImplementation)
{
if (property is { IsIndexer: true, IndexerParameters: not null, })
{
Expand All @@ -1781,7 +1789,7 @@ property.IndexerParameters is not null
property.Type, property.IndexerParameters.Value, useFastForIndexer,
useFastForIndexer ? indexerGetIdRef : null,
cachedBufferRef: indexerGetCachedBufferRef);
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is not ").Append(className)
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is not ").Append(wrapsType)
.Append(' ').Append(wrapsVarName).Append(')').AppendLine();
sb.Append("\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\treturn ").Append(setupVarName).Append(" is null")
Expand Down Expand Up @@ -1814,7 +1822,7 @@ property.IndexerParameters is not null
.AppendDefaultValueGeneratorFor(property.Type, "b.DefaultValue");
if (!property.IsStatic)
{
sb.Append(", ").Append(mockRegistry).Append(".Wraps is not ").Append(className)
sb.Append(", ").Append(mockRegistry).Append(".Wraps is not ").Append(wrapsType)
.Append(" wraps ? null : () => wraps.").Append(property.Name);
}

Expand All @@ -1828,7 +1836,7 @@ property.IndexerParameters is not null
.AppendDefaultValueGeneratorFor(property.Type, $"{mockRegistry}.Behavior.DefaultValue");
if (!property.IsStatic)
{
sb.Append(", ").Append(mockRegistry).Append(".Wraps is not ").Append(className)
sb.Append(", ").Append(mockRegistry).Append(".Wraps is not ").Append(wrapsType)
.Append(" wraps ? null : () => wraps.").Append(property.Name);
}
else
Expand Down Expand Up @@ -1865,7 +1873,7 @@ property.IndexerParameters is not null
sb.Append("\t\t\t\t\t").AppendTypeOrWrapper(property.Type).Append(' ')
.Append(baseResultVarName).Append(" = this.")
.Append(mockRegistryName)
.Append(".Wraps is ").Append(className).Append(' ').Append(wrapsVarName).Append(" ? ")
.Append(".Wraps is ").Append(wrapsType).Append(' ').Append(wrapsVarName).Append(" ? ")
.Append(wrapsVarName).Append('[')
.Append(FormatIndexerParametersAsNames(property.IndexerParameters.Value))
.Append("] : base[")
Expand Down Expand Up @@ -1905,7 +1913,7 @@ property.IndexerParameters is not null
.AppendDefaultValueGeneratorFor(property.Type, "b.DefaultValue");
if (property is { IsStatic: false, } && property.Getter?.IsProtected != true)
{
sb.Append(", ").Append(mockRegistry).Append(".Wraps is ").Append(className)
sb.Append(", ").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType)
.Append(" wraps ? () => wraps.").Append(property.Name).Append(" : () => base.")
.Append(property.Name);
}
Expand All @@ -1924,7 +1932,7 @@ property.IndexerParameters is not null
.AppendDefaultValueGeneratorFor(property.Type, $"{mockRegistry}.Behavior.DefaultValue");
if (property is { IsStatic: false, } && property.Getter?.IsProtected != true)
{
sb.Append(", ").Append(mockRegistry).Append(".Wraps is ").Append(className)
sb.Append(", ").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType)
.Append(" wraps ? () => wraps.").Append(property.Name).Append(" : () => base.")
.Append(property.Name);
}
Expand Down Expand Up @@ -2001,7 +2009,7 @@ property.IndexerParameters is not null
{
AppendRefStructIndexerSetterBody(sb, property, mockRegistry);
}
else if (isClassInterface && !explicitInterfaceImplementation && property.ExplicitImplementation is null)
else if (isClassInterface && !explicitInterfaceImplementation)
{
if (property is { IsIndexer: true, IndexerParameters: not null, })
{
Expand All @@ -2022,7 +2030,7 @@ property.IndexerParameters is not null
.Append(signatureIndex).Append(");")
.AppendLine();

sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(className)
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType)
.Append(' ').Append(wrapsVarName).Append(')').AppendLine();
sb.Append("\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\t").Append(wrapsVarName).Append('[')
Expand Down Expand Up @@ -2050,7 +2058,7 @@ property.IndexerParameters is not null

if (!property.IsStatic && !property.Setter.IsInitOnly)
{
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(className)
sb.Append("\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType)
.Append(" wraps)").AppendLine();
sb.Append("\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\twraps.").Append(property.Name).Append(" = value;").AppendLine();
Expand Down Expand Up @@ -2080,7 +2088,7 @@ property.IndexerParameters is not null
sb.Append("\t\t\t\t{").AppendLine();
if (property.Setter?.IsProtected != true)
{
sb.Append("\t\t\t\t\tif (this.").Append(mockRegistryName).Append(".Wraps is ").Append(className)
sb.Append("\t\t\t\t\tif (this.").Append(mockRegistryName).Append(".Wraps is ").Append(wrapsType)
.Append(' ').Append(wrapsVarName).Append(')').AppendLine();
sb.Append("\t\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\t\t").Append(wrapsVarName).Append('[')
Expand Down Expand Up @@ -2136,9 +2144,9 @@ property.IndexerParameters is not null
}

sb.Append("\t\t\t\t{").AppendLine();
if (property is { IsStatic: false, } && property.Setter?.IsProtected != true)
if (property is { IsStatic: false, Setter: { IsProtected: false, IsInitOnly: false, }, })
{
sb.Append("\t\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(className)
sb.Append("\t\t\t\t\tif (").Append(mockRegistry).Append(".Wraps is ").Append(wrapsType)
.Append(" wraps)").AppendLine();
sb.Append("\t\t\t\t\t{").AppendLine();
sb.Append("\t\t\t\t\t\twraps.").Append(property.Name).Append(" = value;").AppendLine();
Expand Down
37 changes: 37 additions & 0 deletions Tests/Mockolate.ExampleTests/ExampleTests.cs
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Expand Up @@ -267,4 +267,41 @@ public async Task WithOut_ShouldSupportOutParameter(bool returnValue)
await That(result).IsEqualTo(returnValue);
sut.Mock.Verify.TryDelete(It.Is(id), It.IsOut<User?>()).Once();
}

[Fact]
public async Task Wrapping_HiddenMember_ShouldForwardToDeclaringInterface()
{
User alice = new(Guid.NewGuid(), "Alice");
User bob = new(Guid.NewGuid(), "Bob");
MyUserCache realCache = new();
IUserCache sut = IUserCache.CreateMock().Wrapping(realCache);

sut.Users = [alice,];
((IReadOnlyUserCache)sut).Users = [bob,];

// Each interface sees its own member on the wrapped instance.
await That(sut.Users).IsEqualTo([alice,]);
await That(((IReadOnlyUserCache)sut).Users).IsEqualTo([bob,]);
Comment on lines +279 to +284
await That(realCache.CacheUsers).IsEqualTo([alice,]);
await That(realCache.ReadOnlyUsers).IsEqualTo([bob,]);
}

private sealed class MyUserCache : IUserCache
{
public IList<User> CacheUsers { get; private set; } = [];

public IEnumerable<User> ReadOnlyUsers { get; private set; } = [];

public IList<User> Users
{
get => CacheUsers;
set => CacheUsers = value;
}

IEnumerable<User> IReadOnlyUserCache.Users
{
get => ReadOnlyUsers;
set => ReadOnlyUsers = value;
}
}
}
13 changes: 13 additions & 0 deletions Tests/Mockolate.ExampleTests/TestData/IUserCache.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
using System.Collections.Generic;

namespace Mockolate.ExampleTests.TestData;

public interface IReadOnlyUserCache
{
IEnumerable<User> Users { get; set; }
}

public interface IUserCache : IReadOnlyUserCache
{
new IList<User> Users { get; set; }
}
Comment on lines +5 to +13
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