Check outbound queries against a schema snapshot

The GraphQL client validates each query against the server's schema before it sends it. With a checked-in SDL file as the schema, the same check runs in CI and at startup without reaching the server, which matters against a Trax server outside Development: it refuses introspection unless its host admits the client.

1. Check in the schema

Save the server's schema as SDL in the client's repository, for example Schemas/players.graphql, and copy it to the output directory:

<ItemGroup>
  <None Include="Schemas/*.graphql" CopyToOutputDirectory="PreserveNewest" />
</ItemGroup>

2. Point the client at it

using Trax.Api.GraphQL.Client;
using Trax.Api.GraphQL.Client.Trax;
 
builder.Services
    .AddTraxGraphQLClient(new Uri("https://players.example.com/graphql"))
    .UseFileSchema(Path.Combine(AppContext.BaseDirectory, "Schemas", "players.graphql"))
    .UseStartupValidation(typeof(Program).Assembly);

UseStartupValidation stops the host from starting when a query no longer validates. Without the Trax.Api.GraphQL.Client.Trax package, call ValidateGraphQLClientAssembliesAsync after builder.Build() instead.

3. Check it in a test

Build a container with the same registration and validate the assembly that holds the request types. It needs no server.

using Microsoft.Extensions.DependencyInjection;
using Trax.Api.GraphQL.Client;
 
public static class OutboundQueryChecks
{
    public static async Task Every_query_validates_against_the_snapshot()
    {
        var services = new ServiceCollection();
        services
            .AddTraxGraphQLClient(new Uri("https://players.example.com/graphql"))
            .UseFileSchema(Path.Combine(AppContext.BaseDirectory, "Schemas", "players.graphql"));
 
        await using var provider = services.BuildServiceProvider();
        await provider.ValidateGraphQLClientAssembliesAsync(typeof(OutboundQueryChecks).Assembly);
    }
}

The call throws GraphQLValidationException naming the failing query, or InvalidOperationException when no request type belongs to the client. A request for a keyed client is checked with the keyed overload, ValidateGraphQLClientAssembliesAsync(key, assemblies).

4. Keep the snapshot current

The snapshot only proves the queries match the file. Refresh it whenever the server's schema changes, for example in a scheduled job that fetches the schema from a non-production server and fails on a difference, so "the queries validate" and "the snapshot is current" are two separate signals.

SDK Reference

AddTraxGraphQLClient | TraxGraphQLClientBuilder | UseStartupValidation | ValidateGraphQLClientAssembliesAsync | ISchemaProvider