Changes to Variables introduces type unsafety/churn

[srittau]

Description

Please consider the following code, which worked fine with graphql-request 5.1.0:

import { Variables, request } from "graphql-request";

interface Vars {
    bar: string;
}

void request<unknown, Vars>("...", "...", {
    bar: "baz",
});

If unknown variables are used, typescript would fail to compile:

// ...

void request<unknown, Vars>("...", "...", {
    bar: "baz",
    wrong: 123, // <-- compile error
});

With graphql-request 5.2.0, Vars needs to extend from Variables, otherwise typescript complains that "Index signature for type 'string' is missing in type 'Vars'". But extending from Variables (and therefore introducing an index signature) means that unknown variables are not flagged anymore:

import { Variables, request } from "graphql-request";

interface Vars extends Variables {
  bar: string;
}

void request<unknown, Vars>("...", "...", {
  bar: "baz",
  wrong: 123, // <-- not flagged
});

I wasn't unable to identify the exact change that caused it, unfortunately.

[srittau]

And just to leave this here: The workaround/fix is to change

interface Vars {
    bar: string;
}

to

type Vars = {
    bar: string;
}

The problem is that interface Vars is extensible, so typescript doesn't believe it's compatible to Record<...>, while type Vars is not.

[jasonkuhrt]

Thanks @srittau for the issue. Adding a test case and fix for this is on my radar.

[jasonkuhrt]

I haver a PR close to solving this, thanks again.