InsertBefore argument for add()

[sminnee]

To provide some control of the order in which callbacks are called, add an "insert before" argument to add().

Questions:

• should you be able to provide multiple options for insert before, and it will insert before the first one that is found?
• if none are found, should it append to the end of the list or throw an error? If the former it provides a more open-ended way of building up an ordering...

[sminnee]

@unclecheese this came from your comments - do you have some examples of how/why you want to adjust callback ordering in graphql resolvers?

[unclecheese]

Sure. In GraphQL 4, there's another layer of abstraction, "plugins" which are ordered and can order middleware by proxy.

So you have something like:

plugins:
  somePlugin:
    before: anotherPlugin
  anotherPlugin:
    after: somethingElse
  finalPlugin:
    after: '*'

Each of those plugins gets to call ->addResolverMiddleware(), so the order of the middlewares is implicitly set by the order of the plugins. For this library, you'd be looking at just removing that second layer of abstraction.

https://github.com/silverstripe/silverstripe-graphql/blob/cedacb79929745bd1d49bf9309e68c7679c7a90e/src/Schema/Plugin/PluginConsumer.php#L150