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Implement http interceptors #27

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Dec 20, 2023
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5 changes: 5 additions & 0 deletions .changeset/kind-pans-jump.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@open-pioneer/core": minor
---

New helper function `rethrowAbortError`.
11 changes: 11 additions & 0 deletions .changeset/young-wolves-clap.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
---
"@open-pioneer/http": minor
---

New **experimental** feature: request interceptors.
Request interceptors can be registered with the `HttpService` to modify requests before they are sent to a server.
Request interceptors are called automatically by the `HttpService` when they are present as part of the normal request processing.

Example use case: adding an access token (query parameter or header) to requests for a certain resource.

Note that the request interceptor API is experimental: it may change with a new minor release as a response to feedback.
6 changes: 6 additions & 0 deletions pnpm-lock.yaml

Some generated files are not rendered by default. Learn more about how customized files appear on GitHub.

13 changes: 11 additions & 2 deletions src/packages/core/error.ts
Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,8 @@ export function getErrorChain(err: globalThis.Error): globalThis.Error[] {
/**
* Returns true if the error represents an abort error.
*/
export function isAbortError(err: unknown) {
return err && typeof err === "object" && "name" in err && err.name === "AbortError";
export function isAbortError(err: unknown): boolean {
return !!(err && typeof err === "object" && "name" in err && err.name === "AbortError");
}

/**
Expand All @@ -63,6 +63,15 @@ export function throwAbortError(): never {
throw createAbortError();
}

/**
* Throws `err` if it is an abort error. Does nothing otherwise.
*/
export function rethrowAbortError(err: unknown): void {
if (isAbortError(err)) {
throw err;
}
}

/**
* Returns an abort error (`.name` === `"AbortError"`).
*/
Expand Down
313 changes: 313 additions & 0 deletions src/packages/http/HttpServiceImpl.test.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,313 @@
// SPDX-FileCopyrightText: 2023 Open Pioneer project (https://github.com/open-pioneer)
// SPDX-License-Identifier: Apache-2.0
/**
* @vitest-environment happy-dom
*/
import { isAbortError, throwAbortError } from "@open-pioneer/core";
import { createService } from "@open-pioneer/test-utils/services";
import { afterEach, describe, expect, it, vi } from "vitest";
import { HttpServiceImpl } from "./HttpServiceImpl";
import { Interceptor } from "./api";

afterEach(() => {
vi.restoreAllMocks();
vi.useRealTimers();
});

it("should invoke fetch", async () => {
const { service, getRequestCount, getLastRequest } = await setup();
const response = await service.fetch("https://example.com/foo?bar=baz");

expect(getRequestCount()).toBe(1);
expect(getLastRequest()?.url).toMatchInlineSnapshot('"https://example.com/foo?bar=baz"');

expect(response.status).toBe(200);
expect(await response.text()).toBe("ok");
});

it("transports request errors", async () => {
const { service } = await setup({ fetchResponse: errorResponse(404) });
const response = await service.fetch("https://example.com");
expect(response.status).toBe(404);
});

it("performs requests relative to the current origin", async () => {
const { service, getLastRequest } = await setup({
location: "https://example.com/some/path"
});
await service.fetch("/foo?bar=baz");

expect(getLastRequest()?.url).toMatchInlineSnapshot('"https://example.com/foo?bar=baz"');
});

it("performs requests relative to the current location", async () => {
const { service, getLastRequest } = await setup({
location: "https://example.com/some/path/index.html"
});
await service.fetch("./foo?bar=baz");

expect(getLastRequest()?.url).toMatchInlineSnapshot(
'"https://example.com/some/path/foo?bar=baz"'
);
});

it("supports cancellation", async () => {
const abortController = new AbortController();
const { service } = await setup({
async fetchResponse(req) {
await waitForAbort(req.signal);
throwAbortError();
}
});

const promise = service.fetch("./foo?bar=baz", { signal: abortController.signal });
abortController.abort();
await expect(promise).rejects.toSatisfy(isAbortError);
});

describe("before request interceptors", () => {
it("invokes interceptors in order", async () => {
const events: string[] = [];
const interceptors: Interceptor[] = [
{
beforeRequest({ target }) {
events.push("1: " + target.href);
}
},
{
beforeRequest({ target }) {
events.push("2: " + target.href);
}
}
];
const { service } = await setup({ interceptors });
await service.fetch("https://example.com");
expect(events).toMatchInlineSnapshot(`
[
"1: https://example.com/",
"2: https://example.com/",
]
`);
});

it("supports asynchronous interceptors", async () => {
vi.useFakeTimers();

const timeout = 5000;
const interceptor: Interceptor = {
async beforeRequest(params) {
await new Promise((resolve) => {
setTimeout(resolve, timeout);
});

params.target = new URL("https://foo.bar/other-path");
}
};
const { service, getLastRequest } = await setup({ interceptors: [interceptor] });
const promise = service.fetch("https://example.com/bar");
vi.advanceTimersByTime(timeout);
await promise;
expect(getLastRequest()?.url).toMatchInlineSnapshot('"https://foo.bar/other-path"');
});

it("allows interceptors to add query parameters", async () => {
const interceptor: Interceptor = {
beforeRequest(params) {
params.target.searchParams.append("token", "foo");
}
};
const { service, getLastRequest } = await setup({ interceptors: [interceptor] });
await service.fetch("https://example.com/bar");
expect(getLastRequest()?.url).toMatchInlineSnapshot('"https://example.com/bar?token=foo"');
});

it("allows interceptors to replace the target URL", async () => {
const interceptor: Interceptor = {
beforeRequest(params) {
params.target = new URL("https://foo.bar/other-path");
}
};
const { service, getLastRequest } = await setup({ interceptors: [interceptor] });
await service.fetch("https://example.com/bar");
expect(getLastRequest()?.url).toMatchInlineSnapshot('"https://foo.bar/other-path"');
});

it("allows interceptors to add custom http headers", async () => {
const interceptor: Interceptor = {
beforeRequest(params) {
params.options.headers.set("X-CUSTOM-TOKEN", "1234");
}
};
const { service, getLastRequest } = await setup({ interceptors: [interceptor] });
await service.fetch("https://example.com/bar");

const lastRequest = getLastRequest();
expect(lastRequest?.headers.get("X-CUSTOM-TOKEN")).toBe("1234");
});

it("allows interceptors to modify various request options", async () => {
const interceptor: Interceptor = {
beforeRequest(params) {
params.options.credentials = "include";
params.options.method = "PUT";
}
};
const { service, getLastRequest } = await setup({ interceptors: [interceptor] });
await service.fetch("https://example.com/");

const lastRequest = getLastRequest();
expect(lastRequest?.credentials).toBe("include");
expect(lastRequest?.method).toBe("PUT");
});

it("supports per-request context properties", async () => {
const symbol = Symbol("some_symbol");
const props: Record<string | symbol, unknown> = {};
const { service } = await setup({
interceptors: [
{
beforeRequest({ context }) {
props["symbol_prop"] = context[symbol];
props["string_prop"] = context["foo"];
}
}
]
});

await service.fetch("https://example.com", {
context: {
[symbol]: "SYMBOL",
foo: "STRING"
}
});

expect(props).toMatchInlineSnapshot(`
{
"string_prop": "STRING",
"symbol_prop": "SYMBOL",
}
`);
});

it("allows mutation of context from inside interceptors", async () => {
const values: unknown[] = [];
const interceptor: Interceptor = {
beforeRequest({ context }) {
const existing = context.value;
values.push(existing);

context.value = typeof existing === "number" ? existing + 1 : 0;
}
};
const { service } = await setup({
interceptors: [interceptor, interceptor, interceptor, interceptor]
});
await service.fetch("https://example.com");
expect(values).toMatchInlineSnapshot(`
[
undefined,
0,
1,
2,
]
`);
});

it("allows interceptors to spawn another request", async () => {
let calls = 0;
const interceptor: Interceptor = {
async beforeRequest({ context }) {
++calls;

if (context.skipRecurse) {
return;
}

await service.fetch("https://example.com/second", {
context: {
skipRecurse: true
}
});
}
};

const { service, getRequests } = await setup({ interceptors: [interceptor] });
await service.fetch("https://example.com/first");

expect(calls).toBe(2);
expect(getRequests().map((r) => r.url)).toMatchInlineSnapshot(`
[
"https://example.com/second",
"https://example.com/first",
]
`);
});
});

async function setup(options?: {
fetchResponse?: Response | ((req: Request) => Response | Promise<Response>);
location?: string;
interceptors?: Interceptor[];
}) {
const requests: Request[] = [];
const fetchImpl = vi.fn().mockImplementation(async (req: Request) => {
requests.push(req);

const response = options?.fetchResponse;
if (!response) {
return okResponse();
}
return typeof response === "function" ? await response(req) : response;
});

// eslint-disable-next-line @typescript-eslint/no-explicit-any
vi.spyOn(window, "fetch" as any, "get").mockReturnValue(fetchImpl as any);
vi.spyOn(window.location, "href", "get").mockReturnValue(
options?.location ?? "https://example.com:3000/"
);

const service = await createService(HttpServiceImpl, {
references: {
interceptors: options?.interceptors ?? []
}
});
return {
service,
getRequests() {
return requests;
},
getRequestCount() {
return requests.length;
},
getLastRequest() {
return requests[requests.length - 1];
}
};
}

function waitForAbort(signal: AbortSignal): Promise<void> {
return new Promise((resolve) => {
if (signal.aborted) {
return resolve();
}

const handler = () => {
signal.removeEventListener("abort", handler);
resolve();
};
signal.addEventListener("abort", handler);
});
}

function okResponse() {
return new Response("ok", {
status: 200,
statusText: "OK"
});
}

function errorResponse(code = 404) {
return new Response("error´", {
status: code
});
}
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