module: add application/json in accept header when fetching json module

Author: marco-ippolito

lib/internal/modules/esm/fetch_module.js

@@ -145,8 +145,9 @@ function fetchWithRedirects(parsed) {
   }
   const handler = parsed.protocol === 'http:' ? HTTPGet : HTTPSGet;
   const result = (async () => {
+    const extension = parsed.pathname.split('.').pop();
     const req = handler(parsed, {
-      headers: { Accept: '*/*' },
+      headers: { Accept: extension === 'json' ? 'application/json,*/*;' : '*/*;' },
     });
     // Note that `once` is used here to handle `error` and that it hits the
     // `finally` on network error/timeout.

test/es-module/test-http-imports.mjs

@@ -67,6 +67,11 @@ for (const { protocol, createServer } of [
     // ?body sets the body, string
     const server = createServer(function(_req, res) {
       const url = new URL(_req.url, host);
+
+      if (url.pathname.includes('json')) {
+        assert.strictEqual(_req.headers.accept, 'application/json,*/*;');
+      }
+
       const redirect = url.searchParams.get('redirect');
       if (url.pathname === '/not-found') {
         res.writeHead(404);
@@ -203,6 +208,8 @@ for (const { protocol, createServer } of [
       import(notFound.href),
       { code: 'ERR_MODULE_NOT_FOUND' },
     );
+    // Import file with json extension
+    await import(url.href + 'empty.json');
 
     server.close();
   }