UnionGenerator.Analyzers.CodeFixes 0.1.0

UnionGenerator.Analyzers.CodeFixes

Roslyn code fix providers for UnionGenerator analyzers. Provides automatic code fixes and refactorings for common union-related issues detected at compile time.

🚀 Quick Start

1. Install

dotnet add package UnionGenerator.Analyzers.CodeFixes

2. That's it!

Code fixes are automatically available in your IDE. Build your project and you'll see lightbulb icons (💡) in the editor for fixable diagnostics.

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📚 Features

✅ Automatic Code Fixes

One-click fixes for analyzer warnings. Just press Ctrl+. (or Cmd+.) in your IDE.

✅ Safe Refactoring

Code fixes are validated and tested to preserve semantics.

✅ Zero Configuration

Works out-of-the-box with UnionGenerator.Analyzers. No setup required.

✅ IDE Integration

Full integration with Visual Studio, VS Code (with Roslyn extension), and Rider.

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🔧 Supported Fixes

Fix UG4010: Map Union to IActionResult

Diagnostic: Union result returned directly from controller without mapping.

Before:

public Result<User, NotFoundError> GetUser(int id)
{
    return _service.GetUser(id);
}

After (Generated):

public IActionResult GetUser(int id)
{
    return _service.GetUser(id).ToActionResult();
}

What Changed:

• Return type changed from Result<T, E> to IActionResult
• .ToActionResult() call added (maps union to HTTP response)

When Applied:

• Lightbulb appears on method declaration
• Action: "Convert to IActionResult and add ToActionResult()"
• Applied to single method or all methods in controller via batch fix

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Fix UG4011: Add Status Code to Error Type

Diagnostic: Error type used in union doesn't have explicit status code.

Before:

public class CustomError 
{ 
    public string Message { get; set; } 
}

After (Option 1 - Attribute):

[UnionStatusCode(400)]
public class CustomError 
{ 
    public string Message { get; set; } 
}

After (Option 2 - Property):

public class CustomError 
{ 
    public string Message { get; set; }
    public int StatusCode => 400;
}

What Gets Fixed:

• Adds [UnionStatusCode(400)] attribute (or configurable code)
• OR adds StatusCode property returning HTTP code
• Requires manual selection of which approach (attribute vs property)

When Applied:

• Lightbulb appears on error class declaration
• Options shown: "Add [UnionStatusCode] attribute" or "Add StatusCode property"

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Fix UG4012: Make Status Code Explicit

Diagnostic: Status code inferred by convention, but explicit is better.

Before:

public class NotFoundError { }

After:

[UnionStatusCode(404)]
public class NotFoundError { }

What Changed:

• Adds explicit [UnionStatusCode] based on naming convention
• Maps: *NotFound* → 404, *BadRequest* → 400, etc.

When Applied:

• Hidden by default (info diagnostic)
• Enable in .editorconfig if team prefers explicit code
• Lightbulb shows: "Make status code explicit"

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⚙️ Configuration

Enable Fixes in IDE

Visual Studio 2022+:

1. Tools → Options → Text Editor → C# → Code Analysis → General
2. Enable "Enable analyzers from NuGet packages"
3. Rebuild project

VS Code with Roslyn Extension:

1. Install "Roslyn Analyzers" extension
2. Reload window
3. Fixes appear automatically

JetBrains Rider:

1. Settings → Tools → Roslyn Analyzers
2. Enable "UnionGenerator.Analyzers.CodeFixes"
3. Rebuild project

Configure Severity for Batch Fix

In .editorconfig:

# Show all fixable diagnostics
[**/*.cs]
dotnet_diagnostic.UG4010.severity = suggestion
dotnet_diagnostic.UG4011.severity = suggestion
dotnet_diagnostic.UG4012.severity = suggestion

# Or disable specific fixes
dotnet_diagnostic.UG4010.severity = silent  # Don't suggest IActionResult conversion

Scope of Fixes

Single Fix: Apply to one occurrence

• Right-click diagnostic → "Quick Fix" → applies to current line

Scope Fix: Apply to current file

• In some IDEs: "Fix all in document"

Project Fix: Apply to entire project

• Visual Studio: right-click solution, "Run Code Analysis and Fix"
• CLI: dotnet fix --verbosity diag

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📋 Common Scenarios

Scenario 1: Bulk Convert Controllers to IActionResult

Problem: All your controller methods return Result<T, E> instead of IActionResult.

Solution:

1. Open .csproj and add (temporary):

   <PropertyGroup>
       <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
   

2. Build project (forces all UG4010 to appear)
3. Visual Studio → Analyze → Run Code Analysis → Fix Code
4. Remove TreatWarningsAsErrors after batch fix

Result: All controller methods now return IActionResult with .ToActionResult() calls.

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Scenario 2: Standardize Error Status Codes

Problem: Some error types have explicit [UnionStatusCode], others rely on convention.

Solution:

1. In .editorconfig, enable UG4012:

   dotnet_diagnostic.UG4012.severity = suggestion
   

2. Build project
3. Apply fix "Make status code explicit" to all types
4. All errors now have explicit attributes

Result: Clear, consistent error status codes across codebase.

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Scenario 3: Add Missing Status Codes to New Errors

Problem: You create a new error type but forget to add status code.

Solution:

1. Build project (UG4011 warning appears)
2. Click lightbulb (💡) in editor
3. Choose "Add [UnionStatusCode] attribute"
4. Editor prompts for HTTP code
5. Code is inserted automatically

Result: Error type is immediately production-ready.

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🔍 How Code Fixes Work

Detection Phase

Code fix provider listens for these diagnostics:

• UG4010 - Union not mapped to IActionResult
• UG4011 - Error lacks status code
• UG4012 - Convention override recommended

Analysis Phase

For each diagnostic, the code fix:

1. Parses the syntax tree
2. Finds the target method/class
3. Analyzes current code structure
4. Determines appropriate fix

Generation Phase

Code is generated and inserted:

• Preserves original formatting and style
• Maintains indentation
• Respects existing attributes/properties
• Updates using statements if needed

Validation Phase

Generated code is validated:

• Syntax is valid C#
• No naming conflicts
• Type references are correct
• Compilation succeeds

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🛠️ Advanced Usage

Programmatic Code Fixing

If you want to apply fixes programmatically (e.g., in a build step):

// Using Roslyn CodeFixProvider API
var workspace = MSBuildWorkspace.Create();
var project = await workspace.OpenProjectAsync("MyProject.csproj");

foreach (var document in project.Documents)
{
    var semanticModel = await document.GetSemanticModelAsync();
    var diagnostics = await document.GetDiagnosticsAsync();
    
    foreach (var diagnostic in diagnostics)
    {
        if (diagnostic.Id == "UG4010")
        {
            // Apply fix programmatically
            // Details: See Roslyn SDK docs
        }
    }
}

Note: This requires the Roslyn SDK and is beyond typical usage.

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📊 Fix Application Workflow

Build Project
    ↓
Analyzer detects issue (UG4010, UG4011, UG4012)
    ↓
Code fix provider registers fix
    ↓
IDE shows lightbulb (💡)
    ↓
Developer clicks "Quick Fix" or "Apply Fix"
    ↓
Code is generated and inserted
    ↓
Project recompiles
    ↓
✅ Issue resolved

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🎯 Best Practices

✅ DO

• Apply fixes as soon as diagnostics appear (don't let them pile up)
• Review generated code before committing (should be clean and idiomatic)
• Use batch fixes for large-scale refactoring (but review carefully)
• Keep analyzers enabled in CI/CD (prevents regression)
• Document why a fix was declined (if you suppress a diagnostic)

❌ DON'T

• Apply all fixes without reviewing (they're usually correct, but review first)
• Ignore batches of diagnostics and then try to apply all at once
• Use fixes as a substitute for proper error handling design (fix the root cause)
• Suppress diagnostics without documenting why
• Disable code analysis in production builds

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🔗 Related Packages

• UnionGenerator.Analyzers: Diagnostic rules (UG4010, UG4011, UG4012)
• UnionGenerator.AspNetCore: Provides the .ToActionResult() extension that fixes depend on

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🚨 Troubleshooting

Lightbulb Not Appearing

Problem: No fix lightbulb shows up for diagnostics

Solution:

1. Ensure UnionGenerator.Analyzers.CodeFixes NuGet package is installed
2. Rebuild project: dotnet clean && dotnet build
3. Reload IDE window (Visual Studio: File → Recent Projects → Reopen)
4. Check IDE settings: Code analyzers must be enabled

Fix Not Working as Expected

Problem: Applied fix produces incorrect code

Solution:

1. Undo the fix (Ctrl+Z)
2. Check C# language version (11+ recommended)
3. Verify .editorconfig isn't overriding fix behavior
4. Report issue with minimal reproduction case

Status Code Not Suggested

Problem: Fix for UG4011 doesn't suggest the right status code

Solution:

1. UG4011 fix defaults to 400 (Bad Request)
2. Manually change to correct code if different
3. Or use naming convention (NotFound → 404) and apply UG4012 fix instead

Batch Fix Partial Application

Problem: Batch fix applies to some files but not others

Solution:

1. May be due to syntax errors in some files
2. Fix syntax errors first: dotnet build
3. Re-run batch fix operation
4. Check build output for details

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📄 License

MIT License - Part of UnionGenerator project

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✨ Summary

Feature	Benefit
One-Click Fixes	Faster refactoring
Batch Operations	Bulk modernization
IDE Integrated	Works in all major editors
Safe Refactoring	Preserves semantics
Zero Config	Works out-of-box

Quick action: Install the package and press Ctrl+. on any analyzer warning to see available fixes! 🚀