feat(set-context): create set context exchange

exchanges/context/CHANGELOG.md

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+# Changelog
+
+## v0.1.0
+
+**Initial Release**

exchanges/context/README.md

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+<h2 align="center">@urql/exchange-context</h2>
+
+<p align="center"><strong>An exchange for setting operation context in <code>urql</code></strong></p>
+
+`@urql/exchange-context` is an exchange for the [`urql`](https://github.com/FormidableLabs/urql) GraphQL client which can set the operation context both synchronously as well as asynchronously
+
+## Quick Start Guide
+
+First install `@urql/exchange-context` alongside `urql`:
+
+```sh
+yarn add @urql/exchange-context
+# or
+npm install --save @urql/exchange-context
+```
+
+You'll then need to add the `contextExchange`, that this package exposes, to your `urql` Client, the positioning of this exchange depends on whether you set an async setter or not. If you set an async context-setter it's best placed after all the synchronous exchanges (in front of the fetchExchange).
+
+```js
+import { createClient, dedupExchange, cacheExchange, fetchExchange } from 'urql';
+import { contextExchange } from '@urql/exchange-context';
+
+const client = createClient({
+  url: 'http://localhost:1234/graphql',
+  exchanges: [
+    dedupExchange,
+    cacheExchange,
+    contextExchange({
+      getContext: async (operation) => {
+        const token = await getToken();
+        return { ...operation.context, headers: { authorization: token } }
+      },
+    }),
+    fetchExchange,
+  ],
+});
+```
+
+## Maintenance Status
+
+**Active:** Formidable is actively working on this project, and we expect to continue for work for the foreseeable future. Bug reports, feature requests and pull requests are welcome.

exchanges/context/package.json

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+{
+  "name": "@urql/exchange-context",
+  "version": "0.1.0",
+  "description": "An exchange for setting (a)synchronous operation-context in urql",
+  "sideEffects": false,
+  "homepage": "https://formidable.com/open-source/urql/docs/",
+  "bugs": "https://github.com/FormidableLabs/urql/issues",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/FormidableLabs/urql.git",
+    "directory": "exchanges/context"
+  },
+  "keywords": [
+    "urql",
+    "exchange",
+    "context",
+    "formidablelabs",
+    "exchanges"
+  ],
+  "main": "dist/urql-exchange-context",
+  "module": "dist/urql-exchange-context.mjs",
+  "types": "dist/types/index.d.ts",
+  "source": "src/index.ts",
+  "exports": {
+    ".": {
+      "import": "./dist/urql-exchange-context.mjs",
+      "require": "./dist/urql-exchange-context.js",
+      "types": "./dist/types/index.d.ts",
+      "source": "./src/index.ts"
+    },
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "LICENSE",
+    "CHANGELOG.md",
+    "README.md",
+    "dist/"
+  ],
+  "scripts": {
+    "test": "jest",
+    "clean": "rimraf dist extras",
+    "check": "tsc --noEmit",
+    "lint": "eslint --ext=js,jsx,ts,tsx .",
+    "build": "rollup -c ../../scripts/rollup/config.js",
+    "prepare": "node ../../scripts/prepare/index.js",
+    "prepublishOnly": "run-s clean build"
+  },
+  "jest": {
+    "preset": "../../scripts/jest/preset"
+  },
+  "dependencies": {
+    "@urql/core": ">=2.3.6",
+    "wonka": "^6.0.0"
+  },
+  "peerDependencies": {
+    "graphql": "^0.11.0 || ^0.12.0 || ^0.13.0 || ^14.0.0 || ^15.0.0 || ^16.0.0"
+  },
+  "devDependencies": {
+    "graphql": "^16.0.0"
+  },
+  "publishConfig": {
+    "access": "public"
+  }
+}

exchanges/context/src/context.test.ts

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+import { pipe, map, makeSubject, publish, tap } from 'wonka';
+
+import {
+  gql,
+  createClient,
+  Operation,
+  OperationResult,
+  ExchangeIO,
+} from '@urql/core';
+
+import { contextExchange } from './context';
+
+const queryOne = gql`
+  {
+    author {
+      id
+      name
+    }
+  }
+`;
+
+const queryOneData = {
+  __typename: 'Query',
+  author: {
+    __typename: 'Author',
+    id: '123',
+    name: 'Author',
+  },
+};
+
+const dispatchDebug = jest.fn();
+let client, op, ops$, next;
+beforeEach(() => {
+  client = createClient({ url: 'http://0.0.0.0' });
+  op = client.createRequestOperation('query', {
+    key: 1,
+    query: queryOne,
+  });
+
+  ({ source: ops$, next } = makeSubject<Operation>());
+});
+
+it(`calls getContext`, () => {
+  const response = jest.fn(
+    (forwardOp: Operation): OperationResult => {
+      return {
+        operation: forwardOp,
+        data: queryOneData,
+      };
+    }
+  );
+
+  const result = jest.fn();
+  const forward: ExchangeIO = ops$ => {
+    return pipe(ops$, map(response));
+  };
+
+  const headers = { hello: 'world' };
+  pipe(
+    contextExchange({
+      getContext: op => ({ ...op.context, headers }),
+    })({
+      forward,
+      client,
+      dispatchDebug,
+    })(ops$),
+    tap(result),
+    publish
+  );
+
+  next(op);
+
+  expect(response).toHaveBeenCalledTimes(1);
+  expect(response.mock.calls[0][0].context.headers).toEqual(headers);
+  expect(result).toHaveBeenCalledTimes(1);
+});
+
+it(`calls getContext async`, done => {
+  const response = jest.fn(
+    (forwardOp: Operation): OperationResult => {
+      return {
+        operation: forwardOp,
+        data: queryOneData,
+      };
+    }
+  );
+
+  const result = jest.fn();
+  const forward: ExchangeIO = ops$ => {
+    return pipe(ops$, map(response));
+  };
+
+  const headers = { hello: 'world' };
+  pipe(
+    contextExchange({
+      getContext: async op => {
+        await Promise.resolve();
+        return { ...op.context, headers };
+      },
+    })({
+      forward,
+      client,
+      dispatchDebug,
+    })(ops$),
+    tap(result),
+    publish
+  );
+
+  next(op);
+
+  setTimeout(() => {
+    expect(response).toHaveBeenCalledTimes(1);
+    expect(response.mock.calls[0][0].context.headers).toEqual(headers);
+    expect(result).toHaveBeenCalledTimes(1);
+    done();
+  }, 10);
+});

exchanges/context/src/context.ts

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+import {
+  Exchange,
+  makeOperation,
+  Operation,
+  OperationContext,
+} from '@urql/core';
+import { fromPromise, fromValue, mergeMap, pipe } from 'wonka';
+
+export interface ContextExchangeArgs {
+  getContext: (
+    operation: Operation
+  ) => OperationContext | Promise<OperationContext>;
+}
+
+export const contextExchange = ({
+  getContext,
+}: ContextExchangeArgs): Exchange => ({ forward }) => {
+  return ops$ => {
+    return pipe(
+      ops$,
+      mergeMap(operation => {
+        const result = getContext(operation);
+        const isPromise = 'then' in result;
+        if (isPromise) {
+          return fromPromise(
+            result.then((ctx: OperationContext) =>
+              makeOperation(operation.kind, operation, ctx)
+            )
+          );
+        } else {
+          return fromValue(
+            makeOperation(operation.kind, operation, result as OperationContext)
+          );
+        }
+      }),
+      forward
+    );
+  };
+};

exchanges/context/src/index.ts

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+export { contextExchange, ContextExchangeArgs } from './context';

exchanges/context/tsconfig.json

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+{
+  "extends": "../../tsconfig.json",
+  "include": ["src"],
+  "compilerOptions": {
+    "baseUrl": "./",
+    "paths": {
+      "urql": ["../../node_modules/urql/src"],
+      "*-urql": ["../../node_modules/*-urql/src"],
+      "@urql/core/*": ["../../node_modules/@urql/core/src/*"],
+      "@urql/*": ["../../node_modules/@urql/*/src"]
+    }
+  }
+}