Ardalis.Specification Integration for FunctionalDDD

[xavierjohn]

What

Adds FunctionalDdd.ArdalisSpecification - a lightweight integration package that bridges Ardalis.Specification with FunctionalDDD's Railway Oriented Programming patterns.

Why

• Ardalis.Specification is the most popular specification pattern library for .NET (~2M+ downloads)
• It returns null or throws on not found - no Result<T> integration
• FunctionalDDD users need seamless ROP chains with specifications
• Building our own specification library would duplicate existing, mature functionality

Key Features

Extension Method	Returns	Description
FirstOrNotFoundAsync	Result<T>	First match or NotFoundError
SingleOrNotFoundAsync	Result<T>	Single match, NotFoundError if none, ConflictError if multiple

Usage with Value Objects

// Specifications accept value objects, not primitives
public sealed class ProductBySkuSpec : SingleResultSpecification<Product>
{
    public ProductBySkuSpec(Sku sku) =>  // ← Accepts Sku from PrimitiveValueObjects
        Query.Where(p => p.Sku == sku);
}

// Fluent ROP pipeline
var result = await _repository
    .SingleOrNotFoundAsync(new ProductBySkuSpec(sku))
    .EnsureAsync(p => p.IsActive, Error.Validation("Product inactive"))
    .MapAsync(p => new ProductDto(p));

Works with PrimitiveValueObjects Library

// Value objects from FunctionalDdd.PrimitiveValueObjects
public partial class ProductId : RequiredGuid<ProductId>;
public partial class Sku : RequiredString<Sku>;
public partial class ProductName : RequiredString<ProductName>;

// Money from the library
var product = new Product(
    ProductId.Create(Guid.NewGuid()),
    Sku.Create("LAPTOP-001"),
    ProductName.Create("Gaming Laptop"),
    Money.Usd(1299.99m)  // ← Uses library's Money type
);

Files Added

ArdalisSpecification/
├── src/
│   ├── ArdalisSpecification.csproj
│   ├── RepositoryResultExtensions.cs
│   └── ReadRepositoryResultExtensions.cs
├── tests/
│   └── (27 passing tests)
└── README.md

Examples/SpecificationExample/
├── Domain/
│   ├── Product.cs
│   └── ValueObjects.cs          # Uses RequiredGuid, RequiredString
├── Specifications/
│   └── ProductSpecifications.cs # Type-safe specs with value objects
├── Data/
│   └── ProductDbContext.cs      # EF Core with value object converters
└── Program.cs                   # Comprehensive demo

Benefits

Benefit	Description
Type Safety	Specifications accept Sku, not string - compiler prevents errors
Validation First	Invalid input fails at TryCreate, never reaches database
ROP Integration	Seamless chaining with Ensure, Bind, Map, Tap
Minimal Footprint	Just 2 extension classes wrapping mature Ardalis library
No Duplication	Leverages existing ecosystem instead of reinventing

[github-actions]

Test Results

2 583 tests  +27   2 583 ✅ +27   22s ⏱️ -1s
    9 suites + 1       0 💤 ± 0 
    9 files   + 1       0 ❌ ± 0 

Results for commit 64aaf05. ± Comparison against base commit da56ee0.

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.36%. Comparing base (da56ee0) to head (64aaf05).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...pecification/src/ReadRepositoryResultExtensions.cs	93.33%	1 Missing ⚠️
...lisSpecification/src/RepositoryResultExtensions.cs	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #270      +/-   ##
==========================================
+ Coverage   90.33%   90.36%   +0.03%     
==========================================
  Files          99      101       +2     
  Lines        2586     2616      +30     
  Branches      538      544       +6     
==========================================
+ Hits         2336     2364      +28     
- Misses        149      151       +2     
  Partials      101      101              

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