Create a NodeResolver for that type

Oct 13, 2025 by talynt.org 98 views

Introduction

In this article, we will explore a bug in the Hot Chocolate GraphQL library where the QueryContext works on the "node" resolver but not on the "nodes" resolver. We will delve into the steps to reproduce the issue, the expected behavior, and the actual outcome. Additionally, we will discuss the relevant log output and provide additional context to understand the root cause of the problem.

Product and Version

The product used in this article is Hot Chocolate, and the version is 15.1.0-p.11.

Minimal Reproduction

The minimal reproduction link is available at https://github.com/Tommsy64/HotChocolate-NodeResolverBug/blob/main/Program.cs.

Steps to Reproduce

To reproduce the issue, follow these steps:

Create a Node type: Define a Node type in your GraphQL schema.
Create a NodeResolver for that type: Create a NodeResolver for the Node type that has a QueryContext parameter.
Attempt to resolve the node with nodes(ids: [ID!]!): Use the nodes resolver to resolve the node with a list of IDs.

Expected Behavior

The nodes resolver is expected to work with the QueryContext just like the node resolver.

Actual Outcome

However, when attempting to resolve the node with the nodes resolver, a System.InvalidOperationException is thrown with the message "No coercion operator is defined between types 'NodeResolverBugReproduction.Types.Book' and 'NodeResolverBugReproduction.Types.Author'."

Relevant Log Output

There is no relevant log output provided for this issue.

Additional Context

There appears to be a copy-paste error in the HotChocolateExecutionSelectionExtensions class, which is causing the GetOrCreateNodeExpression branch to only be called for the Node resolver and not the Nodes resolver. The if statement should be modified to include the GlobalIdNodesField flag.

if ((flags & FieldFlags.GlobalIdNodeField) == FieldFlags.GlobalIdNodeField
    || (flags & FieldFlags.GlobalIdNodesField) == FieldFlags.GlobalIdNodesField)
{
    return GetOrCreateNodeExpression<TValue>(selection);
}

Conclusion

In conclusion, the QueryContext works on the "node" resolver but not on the "nodes" resolver due to a copy-paste error in the HotChocolateExecutionSelectionExtensions class. By modifying the if statement to include the GlobalIdNodesField flag, we can resolve the issue and ensure that the nodes resolver works with the QueryContext as expected.

Fixing the Issue

To fix the issue, you can modify the HotChocolateExecutionSelectionExtensions class to include the GlobalIdNodesField flag in the if statement. This will ensure that the GetOrCreateNodeExpression branch is called for both the Node and Nodes resolvers.

public static class HotChocolateExecutionSelectionExtensions
{
    // ...

    public static Expression<TValue> GetOrCreateNodeExpression<TValue>(Selection selection)
    {
        // ...

        if ((flags & FieldFlags.GlobalIdNodeField) == FieldFlags.GlobalIdNodeField
            || (flags & FieldFlags.GlobalIdNodesField) == FieldFlags.GlobalIdNodesField)
        {
            return GetOrCreateNodeExpression<TValue>(selection);
        }

        // ...
    }
}

Q: What is the issue with the QueryContext in Hot Chocolate?

A: The issue is that the QueryContext works on the "node" resolver but not on the "nodes" resolver. This means that when you use the node resolver, the QueryContext is available, but when you use the nodes resolver, the QueryContext is not available.

Q: What is the expected behavior of the QueryContext in Hot Chocolate?

A: The expected behavior is that the QueryContext should work on both the "node" and "nodes" resolvers. This means that the QueryContext should be available when using either the node or nodes resolver.

Q: What is the actual behavior of the QueryContext in Hot Chocolate?

A: The actual behavior is that the QueryContext works on the "node" resolver but not on the "nodes" resolver. This means that when you use the node resolver, the QueryContext is available, but when you use the nodes resolver, the QueryContext is not available.

Q: What is the root cause of the issue?

A: The root cause of the issue is a copy-paste error in the HotChocolateExecutionSelectionExtensions class. This error causes the GetOrCreateNodeExpression branch to only be called for the Node resolver and not the Nodes resolver.

Q: How can I fix the issue?

A: To fix the issue, you can modify the HotChocolateExecutionSelectionExtensions class to include the GlobalIdNodesField flag in the if statement. This will ensure that the GetOrCreateNodeExpression branch is called for both the Node and Nodes resolvers.

Q: What is the modified if statement?

A: The modified if statement is:

if ((flags & FieldFlags.GlobalIdNodeField) == FieldFlags.GlobalIdNodeField
    || (flags & FieldFlags.GlobalIdNodesField) == FieldFlags.GlobalIdNodesField)
{
    return GetOrCreateNodeExpression<TValue>(selection);
}

Q: How can I apply the fix?

A: To apply the fix, you can modify the HotChocolateExecutionSelectionExtensions class to include the modified if statement. This will ensure that the GetOrCreateNodeExpression branch is called for both the Node and Nodes resolvers.

Q: What are the benefits of applying the fix?

A: The benefits of applying the fix are:

The QueryContext will work on both the "node" and "nodes" resolvers.
The issue will be resolved, and the application will function as expected.

Q: Are there any potential risks or side effects of applying the fix?

A: There are no potential risks or side effects of applying the fix. The modified if statement is a simple change that will ensure that the GetOrCreateNodeExpression branch is called for both the Node and Nodes resolvers.

Q: How can I verify that the fix has been applied successfully?

A: To verify that the fix has been applied successfully, you can test the application with the nodes resolver and ensure that the QueryContext is available.