OrionGuard.OpenApi 7.0.0

OrionGuard.OpenApi

Makes the OpenAPI document the source of truth: a source generator reads one schema out of it at compile time and emits an IValidator<T> that enforces exactly what the contract says.

dotnet add package OrionGuard
dotnet add package OrionGuard.OpenApi

Hand the document to the compiler:

<ItemGroup>
  <AdditionalFiles Include="openapi.json" />
</ItemGroup>

Then point a partial class at a schema:

using Moongazing.OrionGuard.Core;
using Moongazing.OrionGuard.DependencyInjection;
using Moongazing.OrionGuard.OpenApi;

[OpenApiValidator("openapi.json", "#/components/schemas/Customer")]
public partial class CustomerValidator : IValidator<Customer> { }

public sealed class Customer
{
    public string? Email { get; set; }
    public int Age { get; set; }
}

public static class CheckCustomer
{
    // Validate and ValidateAsync are generated; nothing else is needed.
    public static GuardResult Run(Customer customer) => new CustomerValidator().Validate(customer);
}

You get an ordinary IValidator<Customer> — usable by the ASP.NET Core endpoint filter, the MediatR behavior, or a direct call — whose rules cannot drift from the document, because they are compiled from it on every build. OrionGuard.OpenApi runs inside the compiler, adds no assembly to your output and does not flow to projects that reference yours. This is the inverse of OrionGuard.Swagger, which writes validator constraints into a document.

How the target is bound

• The target must be a partial class; a record is not picked up (OG1005 for a non-partial one). The generated partial repeats the class's accessibility.
• T comes from the IValidator<T> the class implements — implement it directly. The generator will also find T through an AbstractValidator<T> or FluentStyleValidator<T> base, but those already declare Validate and ValidateAsync, so the generated members hide them (CS0108). A class implementing neither gets OG1008 and no code.
• Schema properties bind to public, readable instance properties of T, inherited ones included, by case-insensitive name: firstName binds to FirstName. A schema property with no C# counterpart is skipped silently.
• The document name is matched against the additional files by path suffix first, so specs/openapi.json selects that file; a bare file name falls back to a file-name match, and an ambiguous name raises OG1009.

Which keywords become checks

What is emitted depends on the C# property type, not on the schema's type keyword. A keyword that does not fit the property type is skipped.

A null property skips every check but required; a null instance returns a single NULL error. Errors are keyed by the schema's property name.

The pattern and format checks go through the core package's RegexCache with a one-second match timeout, and the built-in format patterns anchor at the true end of the value (a trailing newline fails) and accept ASCII digits only. A match that times out — a backtracking pattern on hostile input — adds the PATTERN or FORMAT error rather than hanging the request thread.

Diagnostics

The generator skips the affected target, or for OG1006/OG1007 only the affected construct. Error-severity diagnostics fail the build.

What this does not do

• JSON only. A YAML document raises OG1002. Convert it, or emit JSON from your pipeline.
• No composition or polymorphism. allOf, oneOf, anyOf and discriminator raise OG1006, are skipped, and the rest of the schema is still enforced — so a validator can silently be weaker than the document reads.
• Top-level properties only. items schemas and the properties of nested objects are not validated; minItems counts a collection, it does not look inside it.
• type and nullable are read but change nothing. The C# property type decides which checks exist, so a schema saying type: string on an int property yields no string checks rather than an error.
• Same-document $ref only. A pointer into another file does not resolve (OG1004).
• It needs a recent SDK. Built against Roslyn 5.9, so the build SDK must be .NET SDK 10.0.400 or newer; an older one reports CS9057 and skips the generator, leaving Validate unimplemented and the build broken.

Targets

netstandard2.0, as Roslyn components must be; consuming projects target net8.0, net9.0 or net10.0. The JSON reader is bundled, so the package has no other dependencies.

With the rest of OrionGuard

OrionGuard (IValidator<T> and GuardResult) · OrionGuard.Swagger (validators to OpenAPI) · OrionGuard.Generators (validators from attributes) · OrionGuard.AspNetCore

Documentation

• Repository and full documentation
• Changelog

License

MIT. See LICENSE.txt.