Mulitple binding (as attributes) sometimes fail to be properly resolved in a single dependency graph

[W-Sebastian]

Describe the bug
I changed the BindAttributeScenarios.cs from UsageTests to the following:

namespace Pure.DI.UsageTests.Basics.BindAttributeScenario;

using Xunit;

// {
//# using Pure.DI;
// }

public class Scenario
{
    [Fact]
    public void Run()
    {
        // This hint indicates to not generate methods such as Resolve
        // Resolve = Off
// {
        DI.Setup(nameof(Composition))
            .Bind().As(Lifetime.Singleton).To<Facade>()
            .Bind().To<Service>()

            // Composition root
            .Root<IService>("Root");

        var composition = new Composition();
        var service = composition.Root;
        service.DoSomething();
// }
        composition.SaveClassDiagram();
    }
}

// {


interface IAnotherDependency
{
    public void DoSomethingElse();
}

public class AnotherDependency : IAnotherDependency
{
    public void DoSomethingElse()
    {
    }
}

interface IDependency
{
    public void DoSomething();
}

class Dependency : IDependency
{
    public void DoSomething()
    {
    }
}

class Facade
{
    [Bind]
    public IDependency Dependency { get; } = new Dependency();
    
    [Bind]
    public IAnotherDependency SecondDependency { get; } = new AnotherDependency();
}

interface IService
{
    public void DoSomething();
}

class Service(IDependency dep, IAnotherDependency anotherDep) : IService
{
    public void DoSomething() => dep.DoSomething();
}

This results in:

4>BindAttributeScenario.cs(86,27): Error DIE000 : Unable to resolve "Pure.DI.UsageTests.Basics.BindAttributeScenario.IDependency" in Service(Pure.DI.UsageTests.Basics.BindAttributeScenario.IDependency dep<--Pure.DI.UsageTests.Basics.BindAttributeScenario.IDependency), Pure.DI.UsageTests.Basics.BindAttributeScenario.IAnotherDependency anotherDep<--Pure.DI.UsageTests.Basics.BindAttributeScenario.IAnotherDependency)).
4>BindAttributeScenario.cs(86,51): Error CS9113 : Parameter 'anotherDep' is unread.
4>BindAttributeScenario.cs(30,25): Error CS0103 : The name 'Composition' does not exist in the current context
4>BindAttributeScenario.cs(37,31): Error CS0246 : The type or namespace name 'Composition' could not be found (are you missing a using directive or an assembly reference?)

The two bindings provided by the Facade fail to provide anymore.

To Reproduce
Update the BindAttributeScenario to the provided code. Additionally introduce a new unit test in BindAttributeTests that is similar with the provided code and observe the failure.

Expected behavior
Both dependencies should be binded and provided when needed.

Additional context
There is an (ugly) workaround where instead of using Bind attribute we just expose them manually in the factory.
I am also trying to debug the issue but not being familiar with the code base might take a while. If I have any findings I will add them here.

[W-Sebastian]

Changed the title because the issue can also be reproduced with this minimal example, thus removing most of the other variables:

using System;
using Pure.DI;

namespace Sample
{
    internal interface ISecondDependency { }
                           
    internal interface IDependency { }
                           
    internal class Dependency : IDependency, ISecondDependency { }
                           
    internal class BaseComposition
    {
        [Bind]
        public IDependency Dep1 => new Dependency();
                           
        [Bind]
        public ISecondDependency Dep2 => new Dependency();
    }
                           
    static class Setup
    {
        private static void SetupComposition()
        {
            DI.Setup("Composition")
                .Bind().To<BaseComposition>()
                .Root<IDependency>("Service1")
                .Root<ISecondDependency>("Service2");
        }
    }
                           
    public class Program
    {
        public static void Main()
        {
            var composition = new Composition();
        }
    }

[W-Sebastian]

So I had a bit of time today and did some debugging. Here is the root cause however I do not have a fix:

1. All bindings are provided in the same IProcessingNode; this is abstracted under an IEnumerator<IProcessingNode> as a variant;
2. CreateVariants create different versions for each provided Binding so there is a version containing first binding, then a version containing second binding and so on;
3. Each variant is now resolved against a graph;
   a. in the first run no binding is resolved (the variant provides just the main binding);
   b. in the second run, just the first binding is resolved (second one is not provided);
   c. in the third run, just the second binding is resolved (first one is not provided);
4. Code exits with error because the last graph does not contain the first interface resolved.

On short, only the last defined dependency can ever be resolved. This can be tested by binding a third dependency and noticing how now neither of the two gets resolved (because the last run contains the third dependency only).

My intuition is telling me that the variant mechanism was built for something else and the binding attributes should not be part of it however I do not understand why a variant is needed in the first place but it is clear that with the current approach there is no "set" of dependencies to satisfy the graph.

[NikolayPianikov]

@W-Sebastian Thanks for such a thorough investigation.
The problem was that when creating variants, they were grouped by bindingId. But previously, for specific bindings, this bindingId was always 0. There was a bug in the BindingBuilder.Build method.

Fixed in 2.2.14

[NikolayPianikov]

@W-Sebastian thank you!