Table of Contents

Trellis Analyzers

The Trellis analyzers help you write safer, more functional code by detecting common mistakes and suggesting best practices for Railway Oriented Programming.

Installation

dotnet add package Trellis.Analyzers

The analyzer package is automatically included when you install any Trellis package.

Analyzer Rules

Error Handling (TRLS001-TRLS006)

ID Title Severity Has Code Fix
TRLS001 Result return value is not handled Warning ❌
TRLS002 Use Bind instead of Map when lambda returns Result Info ✅
TRLS003 Unsafe access to Result.Value Warning ✅
TRLS004 Unsafe access to Result.Error Warning ✅
TRLS005 Consider using MatchError for error type discrimination Info ❌
TRLS006 Unsafe access to Maybe.Value Warning ✅

Value Objects (TRLS007)

ID Title Severity Has Code Fix
TRLS007 Use Create instead of TryCreate().Value Warning ✅

Type Safety (TRLS008-TRLS011)

ID Title Severity Has Code Fix
TRLS008 Result is double-wrapped Warning ❌
TRLS009 Incorrect async Result usage (blocking) Warning ❌
TRLS010 Use specific error type instead of base Error class Info ❌
TRLS011 Maybe is double-wrapped Warning ❌

Code Quality (TRLS012-TRLS018)

ID Title Severity Has Code Fix
TRLS012 Consider using Result.Combine Info ❌
TRLS013 Consider using GetValueOrDefault or Match Info ✅
TRLS014 Use async method variant for async lambda Warning ✅
TRLS015 Don't throw exceptions in Result chains Warning ❌
TRLS016 Error message should not be empty Warning ❌
TRLS017 Don't compare Result or Maybe to null Warning ❌
TRLS018 Unsafe access to Value in LINQ expression Warning ❌
TRLS019 Combine chain exceeds maximum supported tuple size Error ❌

Severity Levels

  • Error: Code that will not work correctly and must be fixed
  • Warning: Potential runtime errors or correctness issues that should be fixed
  • Info: Suggestions for more idiomatic or maintainable code

Code Fixes

Several analyzers provide automatic code fixes (✅ in the table above):

  • TRLS002: Automatically replaces Map with Bind
  • TRLS003: Wraps unsafe result.Value access in if (result.IsSuccess) guard
  • TRLS004: Wraps unsafe result.Error access in if (result.IsFailure) guard
  • TRLS006: Wraps unsafe maybe.Value access in if (maybe.HasValue) guard
  • TRLS007: Replaces TryCreate().Value with Create()
  • TRLS013: Replaces ternary with GetValueOrDefault() or Match()
  • TRLS014: Replaces sync method with async variant (e.g., Map → MapAsync)

Configuration

Disabling Specific Rules

You can disable specific rules in your .editorconfig:

# Disable TRLS003 for test projects
[**Tests/**/*.cs]
dotnet_diagnostic.TRLS003.severity = none

# Change TRLS007 to suggestion only
dotnet_diagnostic.TRLS007.severity = suggestion

Suppressing Warnings

Use #pragma directives for local suppression:

#pragma warning disable TRLS003
var customer = result.Value; // Intentionally unsafe in test
#pragma warning restore TRLS003

Or use [SuppressMessage] attribute:

[SuppressMessage("Trellis", "TRLS003:Unsafe access to Result.Value",
    Justification = "Test code - validating success scenario")]
public void TestMethod()
{
    var customer = result.Value;
}

Common Patterns

API Controller Pattern

[ApiController]
[Route("api/[controller]")]
public class CustomersController : ControllerBase
{
    [HttpPost]
    public async Task<IActionResult> CreateCustomer(CreateCustomerDto dto)
    {
        return await Result.Combine(
                EmailAddress.TryCreate(dto.Email),
                Name.TryCreate(dto.Name))
            .BindAsync((email, name) => 
                customerService.CreateAsync(email, name))
            .MapAsync(customer => customer.ToDto())
            .MatchAsync(
                onSuccess: dto => Ok(dto),
                onFailure: error => error.ToHttpResult());
    }
}

This pattern avoids all analyzer warnings!

Feedback

Found a false positive or have suggestions? Open an issue on GitHub.

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