Improve C# code quality: fix build errors, add repository pattern, extract constants

[Copilot]

Investigation revealed build failures, tight coupling to Azure Table Storage, and pervasive magic strings reducing maintainability and testability.

Changes

Fix Build Errors

• Generated missing Alias.generated.cs, Accelerators.generated.cs, TokenKind.generated.cs via code generators
• These files are .gitignored and must be generated locally via bootstrap.ps1

Extract Constants

// Before: Magic strings scattered throughout
HelpTableQuery("about_classes")
var client = TableClientFactory.Create("HelpData");

// After: Centralized constants
HelpTableQuery(Constants.AboutTopics.AboutClasses)
var client = TableClientFactory.Create(Constants.TableStorage.HelpDataTableName);

Implement Repository Pattern

public interface IHelpRepository
{
    HelpEntity? GetHelpForCommand(string commandName);
    HelpEntity? GetHelpForCommand(string commandName, string moduleName);
    List<HelpEntity> GetHelpForCommandRange(string commandName);
}

// AstVisitorExplainer now depends on interface, not TableClient
public AstVisitorExplainer(string extentText, IHelpRepository helpRepository, ILogger log, Token[]? tokens)

• TableStorageHelpRepository: Production implementation for Azure Table Storage
• InMemoryHelpRepository: Test double for unit tests without Azurite dependency
• Consolidates duplicate HelpTableQuery methods into repository

Fix Nullable Warnings

• Initialize errorMessage field to empty string (CS8618)
• Mark tokens parameter as nullable (Token[]?)
• Add nullable return types to HelpTableQuery methods
• Simplify redundant null checks

Impact

• Build: 24 errors → 0 errors
• Testability: Can now unit test without Azurite (7 new passing tests)
• Maintainability: All magic strings centralized, reduced code duplication
• Security: CodeQL scan shows 0 alerts

Original prompt

Create a branch and start a thorough investigation in this repo for code smells, inconsistencies, warnings, focussing on the c# solution. I'd like to really improve quality and maintainability of the code. Make it more testable, improve code coverage in unit tests.

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[Jawz84]

LGTM

[Copilot]

Pull request overview

This PR significantly improves C# code quality by fixing build errors, implementing the repository pattern for better testability, and extracting magic strings into constants. The changes reduce tight coupling to Azure Table Storage and enable unit testing without Azurite dependency.

Key Changes

• Fixed 24 build errors by generating missing files and adding proper nullable annotations
• Implemented repository pattern with IHelpRepository, TableStorageHelpRepository, and InMemoryHelpRepository
• Extracted magic strings into a centralized Constants class for improved maintainability
• Added frontend client abstraction (ISyntaxAnalyzerClient) with proper cancellation support
• Added 7 new passing unit tests that don't require Azurite
• Updated all Microsoft documentation URLs from docs.microsoft.com to learn.microsoft.com

Reviewed changes

Copilot reviewed 77 out of 77 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
explainpowershell.analysisservice/Constants.cs	New file centralizing magic strings for table storage, documentation links, and about topics
explainpowershell.analysisservice/Repositories/*.cs	New repository pattern implementation for help data access
explainpowershell.analysisservice/AstVisitorExplainer*.cs	Updated to use IHelpRepository and Constants instead of direct TableClient access
explainpowershell.frontend/Clients/*.cs	New client abstraction with proper error handling and cancellation support
explainpowershell.frontend/Pages/Index.razor.cs	Added Dispose pattern for proper cleanup of AI explanation cancellation tokens
explainpowershell.frontend/Tree.cs	Refactored tree generation algorithm for better performance (O(n) instead of recursive)
explainpowershell.models/*.cs	Added nullable annotations to properties to fix CS8618 warnings
explainpowershell.analysisservice.tests/helpers/*.cs	New InMemoryHelpRepository and TestHelpData for unit testing without Azurite
explainpowershell.helpcollector/HelpCollector.Functions.ps1	New file extracting help collector functions with improved HTML parsing
bootstrap.ps1	Added interactive prompt for profile updates with -UpdateProfile switch
.github/copilot-instructions.md	New file with repository-specific guidelines for Copilot

Comments suppressed due to low confidence (2)

explainpowershell.analysisservice/AstVisitorExplainer_command.cs:173

• Condition is always not null because of ... != ....
  explainpowershell.analysisservice/AstVisitorExplainer_command.cs:177
• Condition is always not null because of ... != ....
  Condition is always not null because of call to method IsNullOrEmpty.

[Copilot]

Injected property should be marked as required or have a null-forgiving operator to avoid nullable warnings. Consider adding = null!; or making it required.

[Copilot]

Field _aiExplanationCts should be marked as nullable (CancellationTokenSource?) since it can be null before assignment and is conditionally disposed with the null-conditional operator.

[Copilot]

Condition is always false because of access to field _disposed.

[Copilot]

Condition is always false because of access to field _disposed.

[Copilot]

These 'if' statements can be combined.

[Copilot]

Get-SynopsisFromUri issues an Invoke-WebRequest to whatever URL is provided in DocumentationLink, which ultimately comes from module help metadata (RelatedLinks, HelpUri, or ProjectUri). Because the add_module_help workflow allows arbitrary GitHub users to request processing of any PowerShell module, a malicious module author can point these help links at attacker-controlled or internal URLs and cause the GitHub runner to make HTTP(S) requests to arbitrary hosts (full SSRF) whenever help is collected. To mitigate this, restrict outbound requests to a strict allowlist of trusted documentation hosts (for example, only learn.microsoft.com / docs.microsoft.com) or avoid making network calls at collection time and rely solely on local help content.