`useOnResolve` incorrectly calls `onResolve` multiple times

[magJ]

Summary

If you have:

• more than one plugin that uses useOnResolve
• & onSchemaChange is triggered more than once

then field.resolve will be wrapped multiple times and onResolve will be triggered multiple times.

Detail

The number of redundant calls will be proportional to the number of useOnResolve plugins, and the number of times onSchemaChange is called.

This happens because the hasWrappedResolve symbol is private to a single plugin instance.

Reproduction

Consider the following scenario:

• An envelop instance is created with two plugins that use useOnResolve, Plugin A and Plugin B
• onSchemaChange fires the first time
• Plugin A wraps the original field.resolve
• Plugin B wraps Plugin A's wrapper.

So far, so good, each plugin will still behave as expected(onResolve is still only called once for each plugin when a resolver is invoked), however:

• The schema is changed, and onSchemaChange is fired a second time.
• Plugin A wraps Plugin B's wrapper of Plugin A's first wrapper
• Plugin B wraps Plugin A's second wrapper of Plugin B's wrapper of Plugin A's first wrapper.

Now when a resolver is called onResolve ends up getting called twice per plugin.

Suggested solution

• A new symbol should be addedSymbol('parentResolver'), this symbol must be a singleton, not private to a single plugin instance.
• When wrapping field.resolve, field[parentResolver] should be set to the original resolver.
• When checking if the plugin has hasWrappedResolveSymbol set, the parentResolver should be recursively checked to ensure that the resolver has not already been wrapped.

_{Side-note, the parentResolver symbol should probably be publicly exported, so that other code that may also be wrapping resolvers, can use it.}

[EmrysMyrddin]

Thank you for your very detailed report!

I'm not sure to understand how we can end up with wrapped resolvers inside the schema on the second onSchemaChange call ? If the schema change, its resolvers should not be wrapped isn't it ?