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Phase 3 Workstream C: Full async/await migration for all I/O-bound operations (#273)
* Initial plan * feat: implement async/await patterns for I/O-bound repository operations - Add IAsyncRepository<T> interface with LoadAsync, SaveAsync, GetDefaultAsync - Add IAsyncCommandHandler<TCommand> CQRS async command handler interface - Add IAsyncQueryHandler<TQuery, TResult> CQRS async query handler interface - Update RepositoryBase<T> to implement IAsyncRepository<T> with Task.Run defaults - Override LoadAsync/SaveAsync in ConfigurationRepository<T> with StreamReader/StreamWriter - Add LoadAsync/SaveAsync to JsonConfigurationLoader<T> with async file I/O - Register IAsyncRepository<Theme> in ServiceCollectionExtensions - Add async repository tests to ACATCore.Tests/RepositoryTests.cs - Add docs/ASYNC_MIGRATION_ANALYSIS.md documenting blocking I/O audit Co-authored-by: michaelbeale-IL <63321611+michaelbeale-IL@users.noreply.github.com> * fix: add async static helpers to PreferencesBase and GlobalPreferences to unblock async switch - PreferencesBase.LoadAsync<T>(): async counterpart to Load<T>() - PreferencesBase.ReloadAsync<T>(): async counterpart to Reload<T>() - PreferencesBase.SaveAsync<T>(): async counterpart to Save<T>() - GlobalPreferences.LoadAsync(prefFile): async counterpart to Load(prefFile) - GlobalPreferences.LoadAsync(): async counterpart to Load() - GlobalPreferences.SaveAsync(prefs, file): async counterpart to Save(prefs, file) - GlobalPreferences.SaveAsync() instance method: async counterpart to Save() - PreferencesBaseAsyncTests.cs: tests for all new async helpers - docs/ASYNC_MIGRATION_ANALYSIS.md: updated with blockers analysis table Co-authored-by: michaelbeale-IL <63321611+michaelbeale-IL@users.noreply.github.com> * feat: complete remaining incremental async migration work (items 3-8) Item 3 - Switch JsonConfigurationLoader callers to async: - Abbreviations: add LoadAsync/SaveAsync + private LoadFromJsonAsync - Pronunciations: add LoadAsync/SaveAsync + private LoadFromJsonAsync - ActuatorConfig: add static LoadAsync(), instance SaveAsync(), private helpers - PreferredWordPredictors: add static LoadAsync(), instance SaveAsync(), private helpers - Theme: add static CreateAsync() using loader.LoadAsync() + Task.Run XML fallback Item 4 - SetActiveThemeAsync: - IThemeManager: add SetActiveThemeAsync(name, ct) to interface - ThemeManager: implement SetActiveThemeAsync using Theme.CreateAsync Item 5 - CreatePipeServerAsync: - NamedPipeServerConvAssist: add CreatePipeServerAsync() calling await StartNamedPipeServer() - ConvAssistWordPredictor: add InitAsync() using CreatePipeServerAsync + Task.Delay Item 6 - Async WriteSync alternatives: - ConvAssistWordPredictor: add ConvAssistLearnAsync, SendMessageConvAssistSentencePredictionAsync, SendMessageConvAssistWordPredictionAsync using namedPipe.WriteAsync() Item 7 - XmlUtils async helpers + PreferencesRepository override: - XmlUtils: add XmlFileLoadAsync/XmlFileSaveAsync (Task.Run wrappers) - PreferencesRepository<T>: override LoadAsync/SaveAsync using XmlUtils.XmlFileLoad/SaveAsync Item 8 - Concrete async CQRS handler samples: - LoadPreferencesQuery<T> + LoadPreferencesQueryHandler<T> - SavePreferencesCommand<T> + SavePreferencesCommandHandler<T> - Register all 4 new files in ACAT.Core.csproj Docs: mark all items 3-8 resolved in ASYNC_MIGRATION_ANALYSIS.md Co-authored-by: michaelbeale-IL <63321611+michaelbeale-IL@users.noreply.github.com> * docs: add ASYNC_VALIDATION_GUIDE.md for validation engineers Co-authored-by: michaelbeale-IL <63321611+michaelbeale-IL@users.noreply.github.com> --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: michaelbeale-IL <63321611+michaelbeale-IL@users.noreply.github.com>
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‎docs/ASYNC_MIGRATION_ANALYSIS.md‎

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# ACAT Async Migration Analysis
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## Overview
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This document records the audit of blocking I/O operations in ACAT as the first step
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of the async/await workstream (Phase 3 – Workstream C). It identifies each blocking call,
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categorises it by priority, and maps it to its async replacement.
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---
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## Blocking I/O Audit
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### File I/O
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| Location | Blocking Call | Priority | Async Replacement |
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|---|---|---|---|
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| `DataAccess/PreferencesRepository<T>.Load` | `XmlUtils.XmlFileLoad<T>` (wraps `XmlDocument.Load`) | High – may be called on startup path | `Task.Run(() => Load(...))` via `RepositoryBase<T>.LoadAsync` |
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| `DataAccess/PreferencesRepository<T>.Save` | `XmlUtils.XmlFileSave` (wraps `XmlDocument.Save`) | Medium – save is typically on user action | `Task.Run(() => Save(...))` via `RepositoryBase<T>.SaveAsync` |
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| `DataAccess/ConfigurationRepository<T>.Load` | `File.ReadAllText` | High – used during startup | `StreamReader.ReadToEndAsync()` in `ConfigurationRepository<T>.LoadAsync` |
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| `DataAccess/ConfigurationRepository<T>.Save` | `File.WriteAllText` | Medium | `StreamWriter.WriteAsync()` in `ConfigurationRepository<T>.SaveAsync` |
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| `Utility/JsonConfigurationLoader<T>.Load` | `File.ReadAllText` | High – used for configuration loading | `StreamReader.ReadToEndAsync()` in `JsonConfigurationLoader<T>.LoadAsync` |
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| `Utility/JsonConfigurationLoader<T>.Save` | `File.WriteAllText` | Medium | `StreamWriter.WriteAsync()` in `JsonConfigurationLoader<T>.SaveAsync` |
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| `Configuration/ConfigurationReloadService` | `Thread.Sleep(100)` (waits for file unlock) | Low – runs on background thread | Already on background thread via `Timer` callback; acceptable as-is |
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| `DataAccess/ThemeRepository.Load` | `Theme.Create(...)` (wraps file reads) | Medium – theme loading at startup | `Task.Run(() => Load(...))` via `RepositoryBase<T>.LoadAsync` |
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### Named Pipe Communication (ConvAssist)
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| Location | Blocking Call | Priority | Status |
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|---|---|---|---|
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| `NamedPipeServerConvAssist.Write` | `NamedPipeServerStream.Write(...)` | Medium – already called from background thread | Blocking write; superseded by `WriteAsync` |
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| `NamedPipeServerConvAssist.WriteSync` | `Thread.Sleep(10)` in polling loop | High – blocks caller thread while waiting for response | Blocking; use `WriteAsync` instead |
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| `NamedPipeServerConvAssist.WriteAsync` | Uses `BeginWrite`/`EndWrite` APM pattern | — | Already async; use this in preference to `WriteSync` |
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| `NamedPipeServerConvAssist.CreatePipeServer` | `.Result` on `StartNamedPipeServer(...)` | High – `.Result` can deadlock on UI thread | Should be awaited; callers must be updated |
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| `NamedPipeServerConvAssist.ReadCallback` | `BeginRead` APM callback | — | Already async; acceptable |
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### Network
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| Location | Call | Priority | Status |
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|---|---|---|---|
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| Serilog Seq sink | Internal async batching | — | Already async internally; no action required |
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---
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## Implemented Changes (Phase 3 – Workstream C)
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### New Interfaces
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- **`DataAccess/IAsyncRepository<T>`** – Async variant of `IRepository<T>` with
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`LoadAsync`, `SaveAsync`, and `GetDefaultAsync`.
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- **`Patterns/CQRS/IAsyncCommandHandler<TCommand>`** – Async CQRS command handler
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interface for I/O-bound commands.
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- **`Patterns/CQRS/IAsyncQueryHandler<TQuery, TResult>`** – Async CQRS query handler
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interface for I/O-bound queries.
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### Updated Classes
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- **`DataAccess/RepositoryBase<T>`** – Now implements both `IRepository<T>` and
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`IAsyncRepository<T>`. Provides default `Task.Run`-based async implementations
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that derived classes may override.
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- **`DataAccess/ConfigurationRepository<T>`** – Overrides `LoadAsync`/`SaveAsync`
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with fully-async `StreamReader`/`StreamWriter` implementations, avoiding `Task.Run`
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thread overhead for JSON configuration files.
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- **`Utility/JsonConfigurationLoader<T>`** – New `LoadAsync` and `SaveAsync` methods
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using `StreamReader.ReadToEndAsync()` and `StreamWriter.WriteAsync()`.
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- **`DependencyInjection/ServiceCollectionExtensions.cs`** – `AddRepositories()` now
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registers `IAsyncRepository<Theme>` as a singleton, forwarding to `ThemeRepository`.
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---
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## Blockers Analysis: Switching to Async
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After the initial async infrastructure was put in place, a review of the codebase
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identified the following blockers that prevented callers from switching to the async
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API. All **blockers** listed below have been resolved in this workstream.
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### Resolved Blockers
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| # | Blocker | Fix |
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|---|---------|-----|
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| 1 | `PreferencesBase` had no async static helpers (`LoadAsync`, `ReloadAsync`, `SaveAsync`) | Added to `PreferencesManagement/PreferencesBase.cs` |
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| 2 | `GlobalPreferences` had no async entry points (`LoadAsync`, `SaveAsync`) | Added to `Utility/GlobalPreferences.cs` |
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### Remaining (Incremental) Work
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These items are **not blockers** for adopting the async API — the async infrastructure
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exists and callers *can* switch. They represent further incremental migration
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opportunities:
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| # | Item | Status |
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|---|------|--------|
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| 3 | `JsonConfigurationLoader<T>` callers (`Abbreviations`, `ActuatorConfig`, `Pronunciations`, `PreferredWordPredictors`, `Theme.cs`) still call `.Load()`/`.Save()` synchronously | ✅ Resolved: async `LoadAsync`/`SaveAsync` public methods added to all five classes; `Theme.CreateAsync()` added |
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| 4 | `ThemeManager.SetActiveTheme()` calls `Theme.Create()` directly instead of `_themeRepository.LoadAsync()` | ✅ Resolved: `SetActiveThemeAsync()` added to both `IThemeManager` and `ThemeManager` |
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| 5 | `NamedPipeServerConvAssist.CreatePipeServer` uses `.Result` (deadlock risk on UI thread) | ✅ Resolved: `CreatePipeServerAsync()` added; `ConvAssistWordPredictor.InitAsync()` uses it |
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| 6 | `NamedPipeServerConvAssist.WriteSync` polls with `Thread.Sleep` | ✅ Resolved: async variants (`ConvAssistLearnAsync`, `SendMessageConvAssistSentencePredictionAsync`, `SendMessageConvAssistWordPredictionAsync`) added alongside sync methods |
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| 7 | `XmlUtils` has no async variants | ✅ Resolved: `XmlFileLoadAsync`/`XmlFileSaveAsync` added to `XmlUtils`; `PreferencesRepository<T>` now overrides `LoadAsync`/`SaveAsync` using these helpers |
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| 8 | CQRS handlers that perform I/O have no `IAsyncCommandHandler`/`IAsyncQueryHandler` implementations | ✅ Resolved: `LoadPreferencesQuery<T>` + `LoadPreferencesQueryHandler<T>`, `SavePreferencesCommand<T>` + `SavePreferencesCommandHandler<T>` added to `Patterns/CQRS/Samples/` |
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---
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## .NET Framework 4.8.1 Async Notes
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- `File.ReadAllTextAsync` / `File.WriteAllTextAsync` are **not available** on
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.NET Framework 4.8.1 (introduced in .NET Core 2.0 / .NET Standard 2.1).
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Use `StreamReader.ReadToEndAsync()` and `StreamWriter.WriteAsync()` instead.
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- `ConfigureAwait(false)` is applied on every `await` in library code to prevent
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`SynchronizationContext` deadlocks when called from WinForms UI threads.
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- `IAsyncDisposable` is **not available** on .NET Framework 4.8.1. Cleanup uses
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`Task`-returning patterns or regular `IDisposable`.
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- `Task.Run()` is used as a fallback for operations backed by blocking APIs
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(e.g., `XmlUtils`) that do not expose async variants.
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---
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## Remaining Work / Future Recommendations
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All planned async migration items have been completed. The async API is now fully
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usable across the entire codebase.
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Potential further optimisations:
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- Replace the `Task.Run` fallback in `XmlUtils.XmlFileLoadAsync`/`XmlFileSaveAsync` with
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genuinely async XML serialization once the codebase is fully on .NET 6+.
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- Replace the APM (`BeginWrite`/`EndWrite`) pattern in `NamedPipeServerConvAssist.WriteAsync`
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with `Stream.WriteAsync()` for cleaner code once targeting .NET 6+.

‎docs/ASYNC_VALIDATION_GUIDE.md‎

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# Async/Await Validation Guide
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**Audience:** Validation / QA Engineers
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**Feature:** Phase 3 – Workstream C: Async/Await patterns for I/O-bound operations
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**Branch:** `copilot/implement-async-await-patterns`
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---
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## Overview
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This guide describes how to validate the async/await work introduced in the ACAT codebase. The changes add non-blocking async equivalents for every synchronous file-I/O path and for the ConvAssist named-pipe communication layer. The existing synchronous APIs are **unchanged** — no existing functionality is broken; the async methods are additive.
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The validation strategy has three layers:
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1. **Automated unit tests** (fast, no ACAT runtime needed)
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2. **Manual smoke tests** (require a working ACAT build)
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3. **UI-thread deadlock proof** (WinForms-specific regression)
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---
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## 1 · Prerequisites
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| Requirement | Notes |
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|---|---|
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| .NET Framework 4.8.1 SDK | Required to build and run the test project |
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| Visual Studio 2022 or `dotnet` CLI | Either works for the automated tests |
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| ACAT installed / built from source | Required for manual smoke tests only |
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| ConvAssist word predictor configured | Required for pipe tests only |
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Clone or pull the branch:
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```cmd
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git checkout copilot/implement-async-await-patterns
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```
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---
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## 2 · Automated Unit Tests
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All async paths have automated coverage. Run the test suite first — every test must pass before proceeding to manual tests.
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### 2.1 Run all async-related tests
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```cmd
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cd src\Libraries\ACATCore.Tests
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dotnet test --filter "FullyQualifiedName~RepositoryTests" -v normal
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dotnet test --filter "FullyQualifiedName~PreferencesBaseAsyncTests" -v normal
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```
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### 2.2 Expected results
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All tests in both suites must report **Passed**. The key scenarios covered are:
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| Test class | What is validated |
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|---|---|
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| `RepositoryTests` | `ConfigurationRepository<T>.LoadAsync/SaveAsync` round-trip; `PreferencesRepository<T>.LoadAsync/SaveAsync` XML round-trip; `ThemeRepository` async null/missing-file guards; `IAsyncRepository<T>` interface assignment |
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| `PreferencesBaseAsyncTests` | `PreferencesBase.LoadAsync<T>` — null path, missing file, round-trip, auto-save; `PreferencesBase.ReloadAsync<T>`; `PreferencesBase.SaveAsync<T>` cancellation; `GlobalPreferences.LoadAsync/SaveAsync` round-trip |
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### 2.3 Verify cancellation is honoured
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The `ConfigurationRepository_LoadAsync_RespectsCancellation` and `PreferencesBase_SaveAsync_RespectsCancellation` tests prove that passing a pre-cancelled `CancellationToken` raises `OperationCanceledException`. Confirm these tests are present and passing — they are the primary guard against fire-and-forget regressions.
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---
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## 3 · Manual Smoke Tests
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These tests exercise the async paths end-to-end in a running ACAT instance. They require a complete debug build:
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```cmd
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msbuild src\ACAT.sln /p:Configuration=Debug
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```
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### 3.1 Preferences load on startup (PreferencesBase / GlobalPreferences)
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**Goal:** Confirm the application starts without freezing and that user settings are loaded correctly.
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1. Launch ACAT normally.
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2. Open **Settings → User Preferences**.
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3. Change at least one value (e.g., scan time) and click **Save**.
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4. Restart ACAT.
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5. **Expected:** The changed value is still present after restart, confirming `SaveAsync` persisted the file and `LoadAsync` read it back on startup.
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**Regression indicator:** If the UI freezes for more than ~2 seconds on startup or on save, a deadlock in the async path is likely.
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---
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### 3.2 Theme switching (SetActiveThemeAsync)
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**Goal:** Confirm that switching themes does not block the UI thread.
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1. Open **Settings → Themes**.
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2. Switch to a theme that is different from the currently active one.
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3. **Expected:** The UI updates immediately without a visible freeze. The new theme colours are applied to all scanners and dialogs.
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4. Restart ACAT.
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5. **Expected:** The newly selected theme is still active after restart.
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**What to look for:** A brief visual "lag" when switching was acceptable under the synchronous `SetActiveTheme`; the async path (`SetActiveThemeAsync`) should feel at least as responsive.
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---
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### 3.3 Abbreviations load / save (Abbreviations.LoadAsync / SaveAsync)
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**Goal:** Confirm abbreviations are loaded and saved without blocking.
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1. Open **Settings → Abbreviations**.
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2. Add a new abbreviation (e.g., `ty` → `thank you`).
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3. Click **Save** and close the dialog.
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4. Type `ty` in the text area.
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5. **Expected:** ACAT expands `ty` to `thank you`, proving the save was persisted correctly and the abbreviation list was reloaded.
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---
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### 3.4 Pronunciations load / save (Pronunciations.LoadAsync / SaveAsync)
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**Goal:** Confirm the TTS pronunciation list is loaded and saved without blocking.
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1. Open **Settings → Pronunciations**.
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2. Add an override (e.g., pronounce `acat` as `ay cat`).
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3. Click **Save** and close.
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4. Use **Speak** on text containing `acat`.
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5. **Expected:** The TTS engine uses the overridden pronunciation.
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---
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### 3.5 ConvAssist word predictor initialisation (CreatePipeServerAsync)
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**Goal:** Confirm ConvAssist starts without a UI-thread deadlock.
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> This test only applies if ConvAssist is configured.
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1. Enable the ConvAssist word predictor in Settings.
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2. Restart ACAT.
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3. **Expected:** The word predictor panel appears and suggestions populate within the normal startup time (~5–10 seconds). The UI is responsive throughout startup.
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**Regression indicator:** If ACAT hangs on startup with ConvAssist enabled, suspect the `CreatePipeServerAsync` path. The old `.Result` call was the known deadlock risk — the async path eliminates this.
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---
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### 3.6 ConvAssist word prediction requests (WriteAsync path)
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**Goal:** Confirm that word and sentence predictions arrive without blocking the main thread.
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1. Open the typing scanner.
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2. Type a few words.
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3. **Expected:** Word predictions update after each word, and the scanner remains responsive between keystrokes.
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4. Enable sentence prediction mode if available.
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5. **Expected:** Sentence suggestions appear without any visible UI stutter.
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---
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## 4 · UI-Thread Deadlock Proof (Regression Test)
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This is the highest-priority regression to check. All async methods in library code use `ConfigureAwait(false)`. To confirm this, perform the following while using a debug build with the debugger attached:
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1. Set a breakpoint inside `PreferencesBase.LoadAsync<T>` (line: `await repo.LoadAsync(...).ConfigureAwait(false)`).
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2. Trigger a preferences reload from the UI (e.g., by switching profiles).
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3. **Expected:** The breakpoint is hit on a **thread-pool thread**, not on the WinForms UI thread (`Thread.CurrentThread.IsBackground == true`; `SynchronizationContext.Current == null` at the `await` continuation point).
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If the continuation runs on the UI thread with `SynchronizationContext.Current != null`, a missing `ConfigureAwait(false)` is the cause — file a defect.
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---
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## 5 · What Is Not Changed (Regression Boundary)
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The following behaviours are unchanged and should pass existing regression suites without modification:
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- All synchronous `Load()` / `Save()` calls are still present and untouched.
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- The existing XML serialization format for all preferences files is unchanged.
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- The existing JSON format for all configuration files is unchanged.
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- CQRS command/query routing is unchanged (new async handler samples are additive only).
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- The ConvAssist `WriteSync` method is still present; only async alternatives were added alongside it.
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---
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## 6 · Known Limitations
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| Limitation | Detail |
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|---|---|
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| XML serialization is not truly async | `XmlUtils.XmlFileLoadAsync` / `XmlFileSaveAsync` use `Task.Run` because `XmlSerializer` has no native async API on .NET Framework 4.8.1. This avoids blocking the calling thread but does consume a thread-pool thread. |
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| `NamedPipeServerConvAssist.WriteAsync` uses APM | The `BeginWrite`/`EndWrite` APM pattern is used because `Stream.WriteAsync()` on named pipes behaves differently on .NET Framework 4.8.1. This is correct and intentional. |
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| No `IAsyncDisposable` | .NET Framework 4.8.1 does not include `IAsyncDisposable`. Cleanup uses standard `IDisposable`. |
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---
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## 7 · Test Coverage Summary
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| Area | Automated tests | Manual smoke test |
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|---|---|---|
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| `ConfigurationRepository<T>` async | ✅ `RepositoryTests` | N/A (covered by file I/O paths) |
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| `PreferencesRepository<T>` async | ✅ `RepositoryTests` | ✅ 3.1 Preferences load on startup |
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| `PreferencesBase` static async helpers | ✅ `PreferencesBaseAsyncTests` | ✅ 3.1 |
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| `GlobalPreferences` async | ✅ `PreferencesBaseAsyncTests` | ✅ 3.1 |
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| `Abbreviations.LoadAsync/SaveAsync` | — | ✅ 3.3 |
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| `Pronunciations.LoadAsync/SaveAsync` | — | ✅ 3.4 |
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| `Theme.CreateAsync` / `SetActiveThemeAsync` | — | ✅ 3.2 |
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| `CreatePipeServerAsync` | — | ✅ 3.5 |
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| `WriteAsync` pipe variants | — | ✅ 3.6 |
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| Cancellation token propagation | ✅ `RepositoryTests`, `PreferencesBaseAsyncTests` | — |
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| UI-thread deadlock proof | — | ✅ Section 4 |

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