fix: default to pesimistic build es2015

esroyo · Oct 18, 2024 · f722243 · f722243
1 parent 1ff5d1d
commit f722243
Show file tree

Hide file tree

Showing 3 changed files with 58 additions and 2 deletions.
diff --git a/src/create-request-handler.test.ts b/src/create-request-handler.test.ts
@@ -68,6 +68,44 @@ Deno.test('should forward the request to $UPSTREAM_ORIGIN keeping the parameters
     );
 });
 
+Deno.test('should replace the user-agent when requesting to $UPSTREAM_ORIGIN if browser is unknown', async () => {
+    const fetchMock = spy((() => fetchReturn()) as typeof globalThis.fetch);
+    const handler = createRequestHandler(
+        baseConfig,
+        undefined,
+        fetchMock,
+    );
+    const req = new Request(`${SELF_ORIGIN}foo?bundle`, {
+        headers: { 'user-agent': 'potato' },
+    });
+    await handler(req);
+    assertEquals(
+        // @ts-ignore
+        (fetchMock.calls?.[0]?.args?.[1]?.headers as Headers).get('user-agent'),
+        'HeadlessChrome/51',
+    );
+});
+
+Deno.test('should NOT replace the user-agent when requesting to $UPSTREAM_ORIGIN if browser is known', async () => {
+    const fetchMock = spy((() => fetchReturn()) as typeof globalThis.fetch);
+    const handler = createRequestHandler(
+        baseConfig,
+        undefined,
+        fetchMock,
+    );
+    const chromeUserAgent =
+        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.0.0 Safari/537.36';
+    const req = new Request(`${SELF_ORIGIN}foo?bundle`, {
+        headers: { 'user-agent': chromeUserAgent },
+    });
+    await handler(req);
+    assertEquals(
+        // @ts-ignore
+        (fetchMock.calls?.[0]?.args?.[1]?.headers as Headers).get('user-agent'),
+        chromeUserAgent,
+    );
+});
+
 Deno.test('should handle $UPSTREAM_ORIGIN with ending slash', async () => {
     const UPSTREAM_ORIGIN = 'https://esm.sh/';
     const fetchMock = spy(() => fetchReturn());

diff --git a/src/create-request-handler.ts b/src/create-request-handler.ts
@@ -5,6 +5,7 @@ import {
     cloneHeaders,
     denyHeaders,
     filterUpstreamHeaders,
+    getBuildTarget,
     isForbidden,
     isJsResponse,
     isNotFound,
@@ -14,7 +15,6 @@ import {
 } from './utils.ts';
 import { toSystemjs } from './to-systemjs.ts';
 import { type Pool } from 'generic-pool';
-import { getBuildTargetFromUA } from 'esm-compat';
 import { basename } from '@std/url';
 import type { Cache, Config, OpenTelemetry, ResponseProps } from './types.ts';
 
@@ -130,7 +130,10 @@ export function createRequestHandler(
 
         // Step: tracing
         const rootSpan = otel.trace.getActiveSpan();
-        const buildTarget = getBuildTargetFromUA(req.headers.get('user-agent'));
+        const originalUserAgent = req.headers.get('user-agent') ?? '';
+        const [buildTarget, upstreamUserAgent] = getBuildTarget(
+            originalUserAgent,
+        );
         const selfUrl = new URL(req.url);
         const basePath = BASE_PATH === '/' ? BASE_PATH : `${BASE_PATH}/`;
         if (selfUrl.pathname === BASE_PATH || selfUrl.pathname === basePath) {
@@ -257,6 +260,11 @@ export function createRequestHandler(
                 req.headers,
                 denyHeaders,
                 filterUpstreamHeaders,
+                (
+                    pair: [string, string] | null,
+                ) => (pair && pair[0] === 'user-agent'
+                    ? [pair[0], upstreamUserAgent]
+                    : pair),
             ),
             redirect: 'manual',
         });

diff --git a/src/utils.ts b/src/utils.ts
@@ -1,5 +1,6 @@
 import request from 'request';
 import { dirname, join } from '@std/url';
+import { getEsmaVersionFromUA } from 'esm-compat';
 import type { HttpZResponseModel, SourceModule } from './types.ts';
 
 export const nodeRequest = async (
@@ -204,3 +205,12 @@ export const buildSourceModule = async (
         return input;
     }
 };
+
+export const getBuildTarget = (userAgent: string): [string, string] => {
+    const esmBuildTarget = getEsmaVersionFromUA(userAgent);
+    if (esmBuildTarget === 'esnext') {
+        // this is the default for unknown browsers
+        return ['es2015', 'HeadlessChrome/51'];
+    }
+    return [esmBuildTarget, userAgent];
+};