Problem

The test Dibix.Tests.TestConfigurationLoaderTests.Load_Lazy_AccessNotInitializedProperty_ThrowsDuringPropertyAccess sporadically fails on Linux Azure Pipeline agents with the following error:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. 
---> System.MethodAccessException: Attempt by method 'Dibix.Tests.TestConfiguration..ctor(Dibix.Testing.ConfigurationInitializationToken)' 
to access method 'Dibix.Tests.NestedTestConfiguration..ctor(Dibix.Testing.ConfigurationInitializationToken)' failed.

Root Cause

In src/Dibix.Testing/Configuration/ConfigurationProxyBuilder.cs at line 54, dynamically generated proxy types are created with TypeAttributes.NotPublic:

TypeBuilder typeBuilder = moduleBuilder.DefineType(type.FullName, attr: TypeAttributes.NotPublic | TypeAttributes.Sealed, parent: type);

When configuration classes have nested complex properties (e.g., TestConfiguration containing NestedTestConfiguration), both proxy types are marked as non-public. When the outer proxy's constructor tries to instantiate the inner proxy constructor, the CLR enforces accessibility rules and fails because a non-public type cannot access another non-public type's constructor in different scopes.

This manifests sporadically on Linux due to timing/JIT compilation differences in how the CLR handles visibility rules for dynamically generated assemblies.

Solution

Change the generated proxy types from NotPublic to Public within the dynamic assembly. In the context of a dynamic assembly created with AssemblyBuilderAccess.Run, marking types as Public makes them accessible to each other within that dynamic assembly context, while still being contained and not exposed outside.

File to modify: src/Dibix.Testing/Configuration/ConfigurationProxyBuilder.cs

Line 54 - Change from:

TypeBuilder typeBuilder = moduleBuilder.DefineType(type.FullName, attr: TypeAttributes.NotPublic | TypeAttributes.Sealed, parent: type);

To:

TypeBuilder typeBuilder = moduleBuilder.DefineType(type.FullName, attr: TypeAttributes.Public | TypeAttributes.Sealed, parent: type);

Expected Outcome

After this change, dynamically generated proxy types will be able to instantiate each other without visibility issues, resolving the sporadic MethodAccessException on Linux Azure Pipeline agents.

References

• Error occurs in: src/Dibix.Testing/Configuration/ConfigurationProxyBuilder.cs line 27
• Stack trace shows the issue originates from nested proxy construction at line 161-162 where DefineComplexProperty emits IL to create nested proxy instances

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: This happens sporadically on linux Azure pipelines agents

Test method Dibix.Tests.TestConfigurationLoaderTests.Load_Lazy_AccessNotInitializedProperty_ThrowsDuringPropertyAccess threw exception:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.MethodAccessException: Attempt by method 'Dibix.Tests.TestConfiguration..ctor(Dibix.Testing.ConfigurationInitializationToken)' to access method 'Dibix.Tests.NestedTestConfiguration..ctor(Dibix.Testing.ConfigurationInitializationToken)' failed.

at Dibix.Tests.TestConfiguration..ctor(ConfigurationInitializationToken)
at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Constructor(Object obj, IntPtr* args)
at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span1 copyOfArgs, BindingFlags invokeAttr) --- End of inner exception stack trace --- at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span1 copyOfArgs, BindingFlags invokeAttr)
at System.Reflection.MethodBaseInvoker.InvokeWithOneArg(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
at Dibix.Testing.ConfigurationProxyBuilder.BuildProxyIfNeeded[T](ConfigurationInitializationToken initializationToken) in /home/vsts/work/1/s/src/Dibix.Testing/Configuration/ConfigurationProxyBuilder.cs:line 27
at Dibix.Testing.TestConfigurationLoader.BindConfigurationInstanceWithLazyValidation[T](IConfiguration configuration, TestContext testContext, Action1 initializationAction) in /home/vsts/work/1/s/src/Dibix.Testing/Configuration/TestConfigurationLoader.cs:line 46 at Dibix.Testing.TestConfigurationLoader.BindConfigurationInstance[T](IConfiguration configuration, TestContext testContext, TestConfigurationValidationBehavior validationBehavior, Action1 initializationAction) in /home/vsts/work/1/s/src/Dibix.Testing/Configuration...