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

PR-URL: #50119 Refs: #50116 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Jacob Smith <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]>

Author: marco-ippolito

lib/internal/modules/esm/fetch_module.js

@@ -134,19 +134,32 @@ function isRedirect(statusCode){
 }
 }
 
+/**
+ * @typedef AcceptMimes possible values of Accept header when fetching a module
+ * @property{Promise<string> | string} default default Accept header value.
+ * @property{Record<string, string>} json Accept header value when fetching module with importAttributes json.
+ * @type{AcceptMimes}
+ */
+constacceptMimes={
+__proto_: null,
+default: '*/*',
+json: 'application/json,*/*;charset=utf-8;q=0.5',
+};
+
 /**
  * @param{URL} parsed
  * @returns{Promise<CacheEntry> | CacheEntry}
  */
-functionfetchWithRedirects(parsed){
+functionfetchWithRedirects(parsed,context){
 constexisting=cacheForGET.get(parsed.href);
 if(existing){
 returnexisting;
 }
 consthandler=parsed.protocol==='http:' ? HTTPGet : HTTPSGet;
 constresult=(async()=>{
+constaccept=acceptMimes[context.importAttributes?.type]??acceptMimes.default;
 constreq=handler(parsed,{
-headers: {Accept: '*/*'},
+headers: {Accept: accept},
 });
 // Note that `once` is used here to handle `error` and that it hits the
 // `finally` on network error/timeout.
@@ -162,7 +175,7 @@ function fetchWithRedirects(parsed){
 'cannot redirect to non-network location',
 );
 }
-constentry=awaitfetchWithRedirects(location);
+constentry=awaitfetchWithRedirects(location,context);
 cacheForGET.set(parsed.href,entry);
 returnentry;
 }
@@ -262,7 +275,8 @@ async function isLocalAddress(hostname){
  * @param{ESModuleContext} context
  * @returns{ReturnType<typeof fetchWithRedirects>}
  */
-functionfetchModule(parsed,{ parentURL }){
+functionfetchModule(parsed,context){
+const{ parentURL }=context;
 const{ href }=parsed;
 constexisting=cacheForGET.get(href);
 if(existing){
@@ -277,10 +291,10 @@ function fetchModule(parsed,{parentURL }){
 'http can only be used to load local resources (use https instead).',
 );
 }
-returnfetchWithRedirects(parsed);
+returnfetchWithRedirects(parsed,context);
 });
 }
-returnfetchWithRedirects(parsed);
+returnfetchWithRedirects(parsed,context);
 }
 
 module.exports={

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

@@ -68,6 +68,11 @@ for (const{protocol, createServer } of [
 constserver=createServer(function(_req,res){
 consturl=newURL(_req.url,host);
 constredirect=url.searchParams.get('redirect');
+
+if(url.pathname==='json'){
+common.mustCall(()=>assert.strictEqual(_req.header.content,'application/json,*/*;charset=utf-8;q=0.5'));
+}
+
 if(url.pathname==='/not-found'){
 res.writeHead(404);
 res.end();
@@ -204,6 +209,13 @@ for (const{protocol, createServer } of [
 {code: 'ERR_MODULE_NOT_FOUND'},
 );
 
+constjsonUrl=newURL(url.href+'json');
+jsonUrl.searchParams.set('mime','application/json');
+jsonUrl.searchParams.set('body','{"x": 1}');
+constjson=awaitimport(jsonUrl.href,{with: {type: 'json'}});
+assert.deepStrictEqual(Object.keys(json),['default']);
+assert.strictEqual(json.default.x,1);
+
 server.close();
 }
 }