Prevent CS0121 (ambiguous method calls) resulting from config binding source gen

[layomia]

From @andrewlock in #44493 (comment):

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One potential issue I can foresee with the design of the generated code (because I've run into a similar issue with my own generators) is around internal classes and InternalsVisibleTo.

The fact that the generated code is always a fixed type (GeneratedConfigurationBinder) in the global namespace, means that something like this will no longer compile:

Project 1:

[assembly:InternalsVisible2(Project2)]
var config = new ConfigurationBuilder().Build();
var settings = new SomeOptions();
section.Bind(settings);

Project 2: (has a <ProjectReference> to Project1)

var config = new ConfigurationBuilder().Build();
var settings = new MoreOptions();
section.Bind(settings); // 👈 error

Gives

[CS0121] The call is ambiguous between the following methods or properties: 'GeneratedConfigurationBinder.Configure<T>(Microsoft.Extensions.DependencyInjection.IServiceCollection, Microsoft.Extensions.Configuration.IConfiguration)' and 'GeneratedConfigurationBinder.Configure<T>(Microsoft.Extensions.DependencyInjection.IServiceCollection, Microsoft.Extensions.Configuration.IConfiguration)'

You might consider it an edge case, but it was one of the first issues I ran into when building my first source generator.

Note: I've just seen that preview 4 bits are going onto NuGet, so apologies if this is no longer relevant! :D (Edit: looks like the preview 3 package is broken for me)

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Issue Details

---

From @andrewlock in #44493 (comment):

---

One potential issue I can foresee with the design of the generated code (because I've run into a similar issue with my own generators) is around internal classes and InternalsVisibleTo.

The fact that the generated code is always a fixed type (GeneratedConfigurationBinder) in the global namespace, means that something like this will no longer compile:

Project 1:

[assembly:InternalsVisible2(Project2)]
var config = new ConfigurationBuilder().Build();
var settings = new SomeOptions();
section.Bind(settings);

Project 2: (has a <ProjectReference> to Project1)

var config = new ConfigurationBuilder().Build();
var settings = new MoreOptions();
section.Bind(settings); // 👈 error

Gives

[CS0121] The call is ambiguous between the following methods or properties: 'GeneratedConfigurationBinder.Configure<T>(Microsoft.Extensions.DependencyInjection.IServiceCollection, Microsoft.Extensions.Configuration.IConfiguration)' and 'GeneratedConfigurationBinder.Configure<T>(Microsoft.Extensions.DependencyInjection.IServiceCollection, Microsoft.Extensions.Configuration.IConfiguration)'

You might consider it an edge case, but it was one of the first issues I ran into when building my first source generator.

Note: I've just seen that preview 4 bits are going onto NuGet, so apologies if this is no longer relevant! :D (Edit: looks like the preview 3 package is broken for me)

Author:	layomia
Assignees:	layomia
Labels:	bug, area-Extensions-Configuration, source-generator
Milestone:	8.0.0

[layomia]

FYI @davidfowl @eerhardt @ericstj re: #44493 (comment).

[davidfowl]

@andrewlock do you also have Configure<T> calls in that assembly?

[layomia]

@tarekgh @eerhardt @ericstj, does it seem reasonable to generate random names to avoid the clashes? Thinking we can make this change when we adopt the Roslyn interceptors feature.

Right now this name clash issue doesn't seem crucial for 8.0, pending feedback from @andrewlock.

[davidfowl]

@tarekgh @eerhardt @ericstj, does it seem reasonable to generate random names to avoid the clashes? Thinking we can make this change when we adopt the Roslyn interceptors feature.

This will fix it.

[tarekgh]

I have done similar things in the options source gen if you want to take a look at #89148

[layomia]

I have done similar things in the options source gen if you want to take a look at #89148

There was discussion in #90340 (comment) about the right approach to avoid name clashes. This needs to be addressed for the options generator, and I'd have to validate interception behavior in the config generator.

[layomia]

We're sticking with the interceptors approach for RC-1, where this problem does not arise. Options generator changes are being tracked in #90990.