Custom validation rules

Readers apply the default validation rule set and return validation errors and warnings in the AsyncApiDiagnostic. Add a ValidationRule<T> to AsyncApiReaderSettings.RuleSet to check a model element during reading. T must implement IAsyncApiElement.

using System;
using ByteBard.AsyncAPI.Models;
using ByteBard.AsyncAPI.Readers;
using ByteBard.AsyncAPI.Validations;

var settings = new AsyncApiReaderSettings();
settings.RuleSet.Add(new ValidationRule<AsyncApiLicense>((context, license) =>
{
    context.Enter("name");
    try
    {
        if (license != null && license.Name != "MIT")
        {
            context.CreateError("LicenseName", "License name must be MIT.");
        }
    }
    finally
    {
        context.Exit();
    }
}));

CreateError and CreateWarning attach the current validation path to the diagnostic. When checking a nested field, use the context's path navigation methods (such as Enter/Exit) around the check so the reported pointer identifies that field. Always balance path entry and exit, including conditional paths. The RuleSet defaults to the built-in rules; adding a rule extends that set. Use ValidationRuleSet.GetEmptyRuleSet() only if you deliberately want to replace the default rules with none and supply your own.

After reading, inspect diagnostics.Errors and diagnostics.Warnings. Rules validate the typed in-memory model, so they do not replace parsing or schema-format handling. For extension-name validation, see extensions.

For example, apply the rule above to this YAML document:

asyncapi: 2.6.0
info:
  title: test
  version: 1.0.0
  license:
    name: apache
  contact:
    name: API Support
    url: https://www.example.com/support
    email: support@example.com

Read the input with the configured reader and inspect the validation result:

var input = """
asyncapi: 2.6.0
info:
  title: test
  version: 1.0.0
  license:
    name: apache
  contact:
    name: API Support
    url: https://www.example.com/support
    email: support@example.com
""";
var document = new AsyncApiStringReader(settings).Read(input, out var diagnostics);
foreach (var error in diagnostics.Errors)
{
    Console.WriteLine($"{error.Pointer}: {error.Message}");
}

The custom rule adds an error at #/info/license/name with the message License name must be MIT. (the reader may also report unrelated default-rule diagnostics). Entering the name path before calling CreateError is what makes the pointer identify the field rather than only the containing license object.