feat: Source-generated mediator with zero runtime dependencies #89
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…iddleware, OnError handling, and Module system Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
…review feedback Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
- Implemented Around middleware with proper composition - Added OnError exception handling pipelines - Enhanced with Stream pipelines (PreStream support) - Added Object overloads (optional) for dynamic dispatch - Implemented Module system for organizing handlers - Added pipeline ordering with PipelineEntry class - Enhanced Builder with IDispatcherBuilder interface - All tests passing (19 dispatcher + 114 other generator tests) - Zero PatternKit runtime dependency maintained - Comprehensive documentation updated - Addressed code review feedback Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
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[WIP] Add source-generated message dispatcher with zero PatternKit dependency
feat: Source-generated mediator with zero runtime dependencies
Jan 21, 2026
JerrettDavis
approved these changes
Jan 22, 2026
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Dependency Review✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.Scanned FilesNone |
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Code Coverage |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #89 +/- ##
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+ Coverage 85.38% 85.82% +0.44%
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Files 143 143
Lines 11890 12205 +315
Branches 1615 1623 +8
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+ Hits 10152 10475 +323
+ Misses 1329 1328 -1
+ Partials 409 402 -7
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Test Results134 tests 134 ✅ 44s ⏱️ Results for commit 3849811. ♻️ This comment has been updated with latest results. |
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🔍 PR Validation ResultsVersion: `` ✅ Validation Steps
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Pull request overview
This PR extends the source-generated dispatcher to provide a richer mediator-style pipeline (Pre/Around/Post/OnError), module-based registration, and optional object-based dispatch, while keeping generated runtime code free of PatternKit dependencies. It also adds tests and documentation to validate and explain the new capabilities, including streaming and module integration.
Changes:
- Introduces a structured pipeline system for commands (Pre, Around, Post, OnError) and Pre hooks for streams using a
PipelineEntrymodel, with ordered composition and anExecuteWithPipelinehelper. - Adds optional object-based overloads for
Send,Publish, andStream, plus a module system viaIModuleandIDispatcherBuilder, and updates the builder to support pipeline registration, stream hooks, and module wiring. - Expands generator tests and the Mediator demo README to cover around middleware, error handling, stream pipelines, object overloads, and the module system.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
test/PatternKit.Generators.Tests/DispatcherGeneratorTests.cs |
Adds end-to-end generator tests for around middleware, OnError handling, stream Pre hooks, object-based Send/Publish overloads, and the module system to validate the generated dispatcher behavior. |
src/PatternKit.Generators/Messaging/DispatcherGenerator.cs |
Extends the generator to emit pipeline infrastructure (PipelineEntry, PipelineType), enhanced command execution with ordered Pre/Around/Post/OnError hooks, optional reflection-based object overloads for commands/notifications/streams, and contracts for IModule/IDispatcherBuilder. |
src/PatternKit.Examples/MediatorComprehensiveDemo/README.md |
Updates example documentation to describe the new middleware pipeline, error handling, module system, object overloads, stream pipelines, and execution flow, with illustrative code snippets. |
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@copilot apply changes based on the comments in this thread |
…t stream test (WIP) - Added try-finally with DisposeAsync for object-based stream enumeration - Fixed README example to use AppDispatcher.Create() instead of dispatcher.Create() - Added test for object-based Stream overload (currently being debugged) - Attempting to fix reflection-based async enumeration Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
… stream test - Added try-finally with DisposeAsync for object-based stream enumeration - Fixed README example to use AppDispatcher.Create() instead of dispatcher.Create() - Added ObjectOverloads_Stream_DispatchesCorrectly test with full coverage - Used reflection on IAsyncEnumerator<T> interface for proper async enumeration - All 134 generator tests passing (20 dispatcher tests including new one) - All 1072 core tests and 437 example tests passing Co-authored-by: JerrettDavis <2610199+JerrettDavis@users.noreply.github.com>
JerrettDavis
approved these changes
Jan 22, 2026
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PR Review Feedback - All Items Addressed ✅
1. ✅ Async Enumerator Disposal (Comment #2715001127)
Issue: Object stream implementation didn't dispose async enumerator, potentially leaking resources.
Fix: Added comprehensive try-finally block with:
IAsyncDisposableinterface check and disposalDisposeAsyncinvocationStream<TRequest, TItem>semanticsCode:
2. ✅ Fixed README Example (Comment #2715001133)
Issue: Example incorrectly used
dispatcher.Create()instead ofAppDispatcher.Create().Fix: Corrected to use static factory method:
3. ✅ Object Stream Test Coverage (Comment #2715001137)
Issue: Object-based
Stream(object request)overload had no tests.Fix: Added
ObjectOverloads_Stream_DispatchesCorrectlytest that:Stream(object)overloadImplementation: Used reflection on
IAsyncEnumerator<T>interface instead of dynamic:IAsyncEnumerable<T>interface on resultGetAsyncEnumeratormethod from interfaceIAsyncEnumerator<T>interface on enumeratorMoveNextAsync()andCurrentvia reflectionTest Results
Technical Details
Why not
dynamic?dynamicfor simpler codeReflection Strategy:
IAsyncEnumerable<T>interface from handler resultGetAsyncEnumerator(CancellationToken)to get enumeratorIAsyncEnumerator<T>interface from enumeratorMoveNextAsync(), check result, getCurrentIAsyncDisposableor reflection onDisposeAsyncAll review feedback addressed and validated! 🎉
Original prompt
This section details on the original issue you should resolve
<issue_title>[Feature] Source-generated message dispatcher (commands, notifications, streams) with zero PatternKit runtime dependency + dual-mode API (class-based + fluent)</issue_title>
<issue_description>## Summary
We want a source generator that produces a standalone message dispatcher for an application:
Critical requirement
The generated output must be 100% independent of PatternKit at runtime:
.g.csfiles may notThe goal is to let teams write “transpilable” / standardized message flows with minimal manual wiring, while keeping the runtime surface small, fast, and distinct.
Goals
G1 — Generated runtime has no dependency on PatternKit
using PatternKit.*in emitted codeG2 — First-class async and streaming
ValueTask)ValueTask)IAsyncEnumerable<T>and streaming pipelines are supportedG3 — Dual-mode consumption
The generated dispatcher supports both:
Mode A: class-based, structured (framework-like)
Mode B: lightweight, fluent (minimal ceremony)
Program.csG4 — AOT-friendly, low-overhead runtime
Non-goals
Desired Public API (generated)
Core concepts
We want three categories of messages:
And a unified dispatcher surface:
Overloads and “ergonomics”
We want overloads that cover common needs and reduce ceremony, while staying distinct:
Commands
Notifications
Streams
Notes
Pipeline behavior model (commands + streams)
We want a pipeline model that can be used in both class-based and fluent modes.
Command pipeline
Proposed delegates: