Support relative request URLs (#34)

Fixes #31 

This takes an approach similar to MSW, whereby we will add the absolute
base url to a request if we're able to. See
https://developer.mozilla.org/en-US/docs/Web/API/Window/fetch#resource
for which absolute base url is used in window vs worker contexts.

Author: IanVS

package.json

@@ -13,10 +13,10 @@
     "type-check": "tsc",
     "test": "vitest run",
     "test:watch": "vitest run --watch",
-    "lint": "eslint src",
-    "lint:fix": "eslint src --fix",
-    "format": "prettier src --write",
-    "format:check": "prettier src --check",
+    "lint": "eslint src tests",
+    "lint:fix": "eslint src tests --fix",
+    "format": "prettier src tests --write",
+    "format:check": "prettier src tests --check",
     "build": "tsc -p tsconfig.build.json"
   },
   "repository": {

src/index.ts

@@ -309,6 +309,33 @@ function requestNotMatches(request: Request, urlOrPredicate: UrlOrPredicate): bo
   return !requestMatches(request, urlOrPredicate);
 }
 
+// Node 18 does not support URL.canParse()
+export function canParseURL(url: string): boolean {
+  try {
+    new URL(url);
+    return true;
+  } catch (err) {
+    return false;
+  }
+}
+
+// Node Requests cannot be relative
+function resolveInput(input: string): string {
+  if (canParseURL(input)) return input;
+
+  // Window context
+  if (typeof window.document !== 'undefined') {
+    return new URL(input, window.document.baseURI).toString();
+  }
+
+  // Worker context
+  if (typeof location !== 'undefined') {
+    return new URL(input, location.origin).toString();
+  }
+
+  return input;
+}
+
 function normalizeRequest(input: RequestInput, requestInit?: RequestInit): Request {
   if (input instanceof Request) {
     if (input.signal && input.signal.aborted) {
@@ -319,12 +346,12 @@ function normalizeRequest(input: RequestInput, requestInit?: RequestInit): Reque
     if (requestInit && requestInit.signal && requestInit.signal.aborted) {
       abort();
     }
-    return new Request(input, requestInit);
+    return new Request(resolveInput(input), requestInit);
   } else {
     if (requestInit && requestInit.signal && requestInit.signal.aborted) {
       abort();
     }
-    return new Request(input.toString(), requestInit);
+    return new Request(resolveInput(input.toString()), requestInit);
   }
 }
 

tests/api.test.ts

@@ -100,41 +100,49 @@ describe('testing mockResponse', () => {
     expect(fetch.mock.calls[0]![0]).toEqual(new URL('https://instagram.com'));
   });
 
-    it('should allow empty response bodies', async () => {
-        fetch.mockResponseOnce(null, { status: 204 });
-        fetch.mockResponseOnce(undefined, { status: 204 });
-        fetch.mockResponseOnce(() => null, { status: 204 });
-        fetch.mockResponseOnce(() => undefined, { status: 204 });
-        fetch.mockResponseOnce(() => Promise.resolve(null), { status: 204 });
-        fetch.mockResponseOnce(() => Promise.resolve(undefined), { status: 204 });
-        fetch.mockResponseOnce({ status: 204 });
-        fetch.mockResponseOnce(() => ({ status: 204 }));
-        fetch.mockResponseOnce(() => Promise.resolve({ status: 204 }));
-        fetch.mockResponseOnce(new Response(null, { status: 204 }));
-        fetch.mockResponseOnce(new Response(undefined, { status: 204 }));
-        fetch.mockResponseOnce(() => new Response(null, { status: 204 }));
-        fetch.mockResponseOnce(() => new Response(undefined, { status: 204 }));
-        fetch.mockResponseOnce(() => Promise.resolve(new Response(null, { status: 204 })));
-        fetch.mockResponseOnce(() => Promise.resolve(new Response(undefined, { status: 204 })));
-        fetch.mockResponseOnce('done');
-
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('');
-        expect(await request()).toBe('done');
-    });
+  it('should support relative request urls', async () => {
+    fetch.mockResponseOnce(JSON.stringify({ data: 'abcde' }), { status: 200 });
+
+    const response = await fetch('folder/file.json').then((res) => res.json());
+
+    expect(response).toEqual({ data: 'abcde' });
+  });
+
+  it('should allow empty response bodies', async () => {
+    fetch.mockResponseOnce(null, { status: 204 });
+    fetch.mockResponseOnce(undefined, { status: 204 });
+    fetch.mockResponseOnce(() => null, { status: 204 });
+    fetch.mockResponseOnce(() => undefined, { status: 204 });
+    fetch.mockResponseOnce(() => Promise.resolve(null), { status: 204 });
+    fetch.mockResponseOnce(() => Promise.resolve(undefined), { status: 204 });
+    fetch.mockResponseOnce({ status: 204 });
+    fetch.mockResponseOnce(() => ({ status: 204 }));
+    fetch.mockResponseOnce(() => Promise.resolve({ status: 204 }));
+    fetch.mockResponseOnce(new Response(null, { status: 204 }));
+    fetch.mockResponseOnce(new Response(undefined, { status: 204 }));
+    fetch.mockResponseOnce(() => new Response(null, { status: 204 }));
+    fetch.mockResponseOnce(() => new Response(undefined, { status: 204 }));
+    fetch.mockResponseOnce(() => Promise.resolve(new Response(null, { status: 204 })));
+    fetch.mockResponseOnce(() => Promise.resolve(new Response(undefined, { status: 204 })));
+    fetch.mockResponseOnce('done');
+
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('');
+    expect(await request()).toBe('done');
+  });
 });
 
 describe('testing mockResponses', () => {
@@ -822,15 +830,15 @@ describe('overloads', () => {
     expect(await request()).toBe('i');
   });
 });
-  
+
 it('works globally', async () => {
-    const fm = createFetchMock(vi);
-    fm.enableMocks();
+  const fm = createFetchMock(vi);
+  fm.enableMocks();
 
-    fetchMock.mockResponseOnce('foo');
-    expect(await request()).toBe('foo');
+  fetchMock.mockResponseOnce('foo');
+  expect(await request()).toBe('foo');
 
-    fm.disableMocks();
+  fm.disableMocks();
 });
 
 it('enable/disable', async () => {

tsconfig.json

@@ -3,7 +3,8 @@
     "module": "NodeNext",
     "moduleResolution": "NodeNext",
     "lib": [
-      "es2022"
+      "es2022",
+      "dom",
     ],
     "baseUrl": "./",
     "paths": {

vitest.config.ts

@@ -6,4 +6,7 @@ export default defineConfig({
       'vitest-fetch-mock': './src/index',
     },
   },
+  test: {
+    environment: 'jsdom',
+  },
 });