Allow to use consts in types as service KeySelector

[Dreamescaper]

[GenerateServiceRegistrations(AssignableTo = typeof(IService), KeySelector = "Key")]
public partial static IServiceCollection AddKeyedServices(this IServiceCollection services);

public class MyService1 : IService 
{
    public const string Key = "MSR1";
}
public class MyService2 : IService 
{
    public const string Key = "MSR2";
}

[Copilot]

Pull Request Overview

This PR updates the service registration code to support using constant fields or static properties as key selectors instead of only static methods. Key changes include:

• Introducing a new KeySelectorType enum and updating code paths in AttributeModel, DependencyInjectionGenerator, and related files.
• Modifying tests and documentation to reflect the changes.
• Removing the diagnostic for a missing key selector method in favor of treating the key selector as a type member when a matching static method isn’t found.

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
ServiceScan.SourceGenerator.Tests/AddServicesTests.cs	Added a new test case to validate using constant fields as key selectors.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.ParseMethodModel.cs	Updated key selector lookup logic to support type members.
ServiceScan.SourceGenerator.Playground/Services.cs	Revised service classes to include constant Key members and updated naming values.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs	Modified registration generation to rely on the new KeySelectorType handling.
ServiceScan.SourceGenerator/Model/AttributeModel.cs	Replaced KeySelectorGeneric with KeySelectorType and updated key selector determination.
ServiceScan.SourceGenerator.Tests/DiagnosticTests.cs	Removed obsolete diagnostic test for non-existing key selector methods.
ServiceScan.SourceGenerator/GenerateAttributeSource.cs	Updated XML documentation to describe the dual key selector support.
README.md	Revised documentation to include guidance on using const fields or static properties as key selectors.
ServiceScan.SourceGenerator.Playground/ServiceCollectionExtensions.cs	Updated attribute usage to include the new KeySelector property.
ServiceScan.SourceGenerator/DiagnosticDescriptors.cs	Removed descriptor for missing key selector method.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.FindServicesToRegister.cs	Adjusted parameter usage from KeySelectorGeneric to KeySelectorType.
ServiceScan.SourceGenerator/Model/ServiceRegistrationModel.cs	Updated model to reflect the new key selector handling.

Comments suppressed due to low confidence (1)

ServiceScan.SourceGenerator/Model/AttributeModel.cs:49

• [nitpick] Consider adding a comment to explain why the code falls back to 'TypeMember' for key selectors when no matching static method is found.

keySelectorType = Model.KeySelectorType.TypeMember;

[Copilot]

[nitpick] The class name 'MyServ111111111ice3' appears to contain a typo. Consider renaming it to 'MyService3' or another appropriate name.

Suggested change

	public class MyServ111111111ice3 : IService
	public class MyService3 : IService

[Copilot]

Pull Request Overview

This PR introduces support for using constant fields and static properties as key selectors for service registrations, updating both source generation and diagnostic behaviors accordingly.

• Replace the previous KeySelector method diagnostic with a fallback to a TypeMember when the key selector method is not found.
• Update various components (attribute model, registration model, generator, and documentation) to consistently use the new KeySelectorType enum.
• Remove outdated tests and diagnostics related to the missing KeySelector method.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ServiceScan.SourceGenerator.Tests/AddServicesTests.cs	Adds a new test to verify registration when using constant fields as key selectors.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.ParseMethodModel.cs	Updates key selector handling logic to use KeySelectorType and removes the diagnostic for a missing static method.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.cs	Switches to use KeySelector and KeySelectorType in generating the service registrations.
ServiceScan.SourceGenerator/Model/AttributeModel.cs	Replaces the old boolean KeySelectorGeneric with a robust KeySelectorType enum.
ServiceScan.SourceGenerator/GenerateAttributeSource.cs	Updates the documentation to reflect the support for both method and constant/key property selectors.
ServiceScan.SourceGenerator.Tests/DiagnosticTests.cs	Removes the obsolete test for missing KeySelector method, aligning with the new behavior.
ServiceScan.SourceGenerator/DiagnosticDescriptors.cs	Removes the diagnostic descriptor for a missing KeySelector method.
ServiceScan.SourceGenerator/DependencyInjectionGenerator.FindServicesToRegister.cs and ServiceRegistrationModel.cs	Adjusts references to use KeySelectorType in place of the old KeySelectorGeneric.

Comments suppressed due to low confidence (2)

ServiceScan.SourceGenerator.Tests/DiagnosticTests.cs:202

• The removal of the 'KeySelectorMethodDoesNotExist' test reduces coverage for scenarios where a KeySelector method is missing. If the change in behavior (falling back to TypeMember) is intentional to support constants and static properties, consider adding a test to verify that an absent method correctly results in a fallback rather than a silent failure.

[Fact] public void KeySelectorMethodDoesNotExist() { ... }

ServiceScan.SourceGenerator/Model/AttributeModel.cs:40

• [nitpick] Falling back to KeySelectorType.TypeMember when a static key selector method is not found could lead to ambiguity if a user mistakenly misspells the member name. Consider adding documentation or a warning to guide users in cases where the intended member is absent.

if (keySelectorMethod != null) { ... } else { keySelectorType = Model.KeySelectorType.TypeMember; }