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SWGQL03: GraphQL extension class static

Overview​

Rule ID: SWGQL03
Category: GraphQL
Severity: Error
Status: Enabled by default

Description​

This rule enforces that classes annotated with [ExtendObjectType] must be declared as static. The [ExtendObjectType] attribute is used to extend GraphQL types defined in HotChocolate, and these extension classes should be static to properly support the GraphQL type system.

When This Rule Triggers​

The analyzer reports a diagnostic when:

  • A class is decorated with the [ExtendObjectType] attribute
  • The class is not declared as static

Why This Matters​

HotChocolate Type Extension Pattern​

In HotChocolate, when extending an existing GraphQL object type:

  • The class must be static to represent a pure type extension
  • Instance state in extension classes can lead to unexpected behavior
  • Non-static extension classes violate HotChocolate's type system conventions

This rule ensures your GraphQL schema extensions follow HotChocolate best practices.

How to Fix​

Add the static modifier to the class declaration:

// ❌ WRONG - non-static extension class
[ExtendObjectType(typeof(User))]
public class UserExtensions
{
    [GraphQLName("fullName")]
    public string GetFullName([Parent] User user)
    {
        return $"{user.FirstName} {user.LastName}";
    }
}

// ✅ CORRECT - static extension class
[ExtendObjectType(typeof(User))]
public static class UserExtensions
{
    [GraphQLName("fullName")]
    public static string GetFullName([Parent] User user)
    {
        return $"{user.FirstName} {user.LastName}";
    }
}

Example​

using HotChocolate.Types;

// ⚠️ SWGQL03 - Non-static extension class
[ExtendObjectType(typeof(Post))]
public class PostExtensions
{
    public string GetSummary([Parent] Post post)
    {
        return post.Content.Length > 100 
            ? post.Content.Substring(0, 100) + "..." 
            : post.Content;
    }
}

// ✅ CORRECT - Static extension class
[ExtendObjectType(typeof(Post))]
public static class PostExtensions
{
    public static string GetSummary([Parent] Post post)
    {
        return post.Content.Length > 100 
            ? post.Content.Substring(0, 100) + "..." 
            : post.Content;
    }
}

Configuration​

This rule is enabled by default as an error. To change its severity:

[*.cs]
dotnet_diagnostic.SWGQL03.severity = warning

To disable it:

[*.cs]
dotnet_diagnostic.SWGQL03.severity = none

See Also​