Update Context Types

[samchungy]

Checklist:

• If this PR contains changes to the library itself (not necessary for e.g. docs updates), please include a changeset (see CONTRIBUTING.md)
• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests

The tl;dr

• The context type on all operations must now extend OperationContext (Record<string, any>) and defaults to Partial<DefaultContext>
• The ApolloClient constructor context field now requires a non partial DefaultContext.

In Depth

I was trying to work with @phryneas comment here: apollographql/apollo-client-nextjs#103 (comment)

by setting a defaultContext type:

eg.

declare module '@apollo/client' {
  export interface DefaultContext {
    appContext: {
      foo: string
    }
    triggerBehaviour?: boolean
  }
}

However, this had cascading effects to the other operations such as useQuery where suddenly the operation inputs were expecting appContext to be in the context which is incorrect as we should only require a partial of the default context to allow for overwriting

So I decided to go and fix the query type but realised the mutation type allows the Context to be set:

apollo-client/src/core/watchQueryOptions.ts

Line 252 in 6496b25

context?: TContext;

So in the name of consistency I went to try and add generics for the Query types and many changes later here we are.

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Latest commit: 4fe7305

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[samchungy]

I created a new type called OperationContext to represent Record<string, any>. I wanted to call it Context but

apollo-client/src/react/types/types.ts

Line 43 in 6496b25

export type { DefaultContext as Context } from "../../core/index.js";

that name is already taken

[samchungy]

Update the types here to reflect that users only need to pass in a partial of the context.

apollo-client/src/link/utils/createOperation.ts

Lines 8 to 15 in 4ebebf0

	const setContext: Operation["setContext"] = (next) => {
	if (typeof next === "function") {
	context = { ...context, ...next(context) };
	} else {
	context = { ...context, ...next };
	}
	};
	const getContext: Operation["getContext"] = () => ({ ...context });

But I also thought that users might want to strictly type what they want to return here so I've given the flexibility to pass in TContext.

[samchungy]

I'm not particularly sure what the defaulting is for here but I decided to leave it in to avoid any breaking change and am choosing to cast here instead.

[samchungy]

Not sure why the tests are failing as there are no code changes in this PR

[samchungy]

Should this be required? If we're typing DefaultContext, I would expect this to be filled on client creation?

apollo-client/src/core/ApolloClient.ts

Line 119 in 6496b25

defaultContext?: Partial<DefaultContext>;

If they need it to be optional they could declare it themselves while extending it

[phryneas]

Hi Sam,
I just wanted to leave quick feedback: we're all just back from conferences and will likely need a few days to catch up on everything. The PR is very welcome, but I'll need to free up some headspace to look at it thoroughly :)

[samchungy]

Hi Sam, I just wanted to leave quick feedback: we're all just back from conferences and will likely need a few days to catch up on everything. The PR is very welcome, but I'll need to free up some headspace to look at it thoroughly :)

No problems, we're all busy people! Fully understand, thanks for the reply

[samchungy]

I think this makes sense, if you are expecting something to always be in here, you would declare it as Required on the default context?

Unless we're intentionally making this Partial so you could type things like headers: Record<string, string> as Apollo seems to always inject these