fix: Multiple bug fixes and enhancements to source generator

[glennawatson]

This PR addresses four major bugs and adds comprehensive test coverage for the Splat.DI.SourceGenerator. All changes maintain compatibility with the incremental generator pipeline and follow AOT-first design principles.

Fixes #282 - Analyzer false positives on non-Splat Register methods
Problem: ConstructorAnalyzer triggered SPLATDI001 warnings on ALL classes with multiple constructors, including non-Splat code like DialogManager.Register<TView, TContext>().

Root Cause: Used RegisterSymbolAction(SymbolKind.NamedType) which analyzed every class/struct in the compilation, regardless of whether it was used with Splat DI.

Solution: Changed to RegisterOperationAction(OperationKind.Invocation) to only analyze types actually registered via SplatRegistrations.Register/RegisterLazySingleton. Added IsSplatRegistrationsMethod() helper to filter invocations.

Impact: Eliminates false positives while maintaining detection of real Splat DI issues.

Tests: 5 new tests added, 114 analyzer tests passing.

Fixes #120 - Missing dependencies silently return null
Problem: Generated code used resolver.GetService(typeof(T)) which returns null when dependencies are missing, causing runtime NullReferenceException instead of clear error messages.

Solution:

• Switched to generic GetService() API (no cast needed, better for AOT)
• Added null-coalescing operator with descriptive InvalidOperationException
• Error messages include dependency type name and contract (if applicable)

Generated Code Change:
Before: (IFoo)resolver.GetService(typeof(IFoo))
After: resolver.GetService() ?? throw new InvalidOperationException("Dependency 'IFoo' not registered...")

Impact: Early failure detection at registration time with clear error messages. All 342 snapshot tests updated.

Tests: All existing tests updated and verified.

Fixes #72 - IEnumerable dependency injection support
Problem: Constructor parameters of type IEnumerable were treated like regular dependencies, calling GetService(typeof(IEnumerable)) which returns null. Should call GetServices() to retrieve all registered implementations.

Solution:

• Extended ConstructorParameter model with IsCollection and CollectionItemType fields
• Added IEnumerable detection in ExtractConstructorParameters (similar to Lazy)
• Generate GetServices() calls for collection parameters (returns IEnumerable, never null)

Generated Code:
resolver.GetServices() for IEnumerable parameters resolver.GetServices("contract") when using contracts

Impact: Enables injection of multiple implementations, enables common DI patterns.

Tests: 9 new tests added covering contracts and scenarios.

Validates and closes #137 - Generic type registration support
Status: Already working correctly via ToDisplayString(FullyQualifiedFormat). Added comprehensive test coverage to prevent regressions.

Tests Added:

• Single type parameter: Register<IAppUpdateService, AppUpdateService>()
• Multiple type parameters: Register<ICache, Cache<string, int>>()
• Nested generics: Register<IRepository, Repository<List>>()

Impact: 27 new tests (3 scenarios × 3 contracts × 3 frameworks) confirm generic types work correctly with fully-qualified names.

Additional Improvements

• All generated code now uses generic APIs (GetService, Register, GetServices) instead of Type-based APIs for better AOT compatibility and performance
• Test infrastructure updated to include SplatRegistrations class in test compilations
• All tests follow TUnit framework patterns with proper async/await usage

Breaking Changes

1. Generated GetService calls now throw exceptions if dependencies are missing
2. ConstructorParameter record has 2 new fields (IsCollection, CollectionItemType) - internal API
3. Generated code uses generic GetService() and GetServices() instead of typeof() variants

Test Results

• Total: 633 tests (36 new tests added)
• Failed: 0
• Succeeded: 633
• New coverage: 5 analyzer + 4 IEnumerable + 27 generic type tests

All changes follow ReactiveUI contribution guidelines with proper formatting, XML documentation, and no LINQ in hot paths.

[codecov]

Codecov Report

❌ Patch coverage is 91.57895% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.03%. Comparing base (269560b) to head (6abed78).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ncyInjection.Analyzer/Analyzers/AnalyzerHelpers.cs	87.87%	1 Missing and 7 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #287      +/-   ##
==========================================
+ Coverage   87.85%   94.03%   +6.18%     
==========================================
  Files          14       17       +3     
  Lines         815      838      +23     
  Branches      145      145              
==========================================
+ Hits          716      788      +72     
+ Misses         58       19      -39     
+ Partials       41       31      -10     

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[Copilot]

Pull request overview

This PR implements multiple critical bug fixes and feature enhancements for the Splat.DI.SourceGenerator, addressing analyzer false positives, missing dependency handling, and IEnumerable injection support.

Changes:

• Switches from reflection-based typeof() API to generic GetService<T>() for better AOT compatibility
• Adds null-coalescing with descriptive InvalidOperationException for missing dependencies
• Implements IEnumerable<T> parameter detection using GetServices<T>()
• Adds comprehensive test coverage (36 new tests across 4 bug fixes)
• Updates ConstructorParameter model with IsCollection and CollectionItemType fields

Reviewed changes

Copilot reviewed 263 out of 263 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
Models/ConstructorParameter.cs	Extended record with IsCollection and CollectionItemType fields for IEnumerable support
Generator.cs	Refactored dependency resolution to use generic APIs, added null checks with exceptions, implemented IEnumerable detection
Constants.cs	Fixed indentation of attribute class definitions (formatting only)
RegisterTests.cs	Added 4 new test methods for IEnumerable, generic types, and property injection scenarios
RegisterLazySingletonTests.cs	Added 2 new test methods for lazy singleton with IEnumerable and contracts
Models/*Tests.cs	Updated unit tests to match new ConstructorParameter constructor signature
*.verified.cs (342 files)	Updated snapshot tests reflecting new generic API usage and error handling

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.