esm: fix http(s) import via custom loader

lib/internal/modules/esm/loader.js

@@ -351,12 +351,21 @@ class ESMLoader {
       // The request & response have already settled, so they are in
       // fetchModule's cache, in which case, fetchModule returns
       // immediately and synchronously
-      url = fetchModule(new URL(url), { parentURL: url }).resolvedHREF;
-      // This should only occur if the module hasn't been fetched yet
-      if (typeof url !== 'string') { // [2]
-        throw new ERR_INTERNAL_ASSERTION(`Base url for module ${url} not loaded.`);
+      const module = fetchModule(new URL(url), { parentURL: url });
+
+      if (typeof module?.resolvedHREF === 'string') { // [2]
+        url = module.resolvedHREF;
+      } else { // This should only occur if the module hasn't been fetched yet
+        if (getOptionValue('--experimental-network-imports')) {
+          throw new ERR_INTERNAL_ASSERTION(
+            `Base url for module ${url} not loaded.`
+          );
+        } else {
+          url = module;
+        }
       }
     }
+
     return url;
   }
 

lib/internal/modules/esm/module_job.js

@@ -76,7 +76,11 @@ class ModuleJob {
       // these `link` callbacks depending on each other.
       const dependencyJobs = [];
       const promises = this.module.link(async (specifier, assertions) => {
-        const baseURL = this.loader.getBaseURL(url);
+        const base = await this.loader.getBaseURL(url);
+        const baseURL = typeof base === 'string' ?
+          base :
+          base.resolvedHREF;
+
         const jobPromise = this.loader.getModuleJob(specifier, baseURL, assertions);
         ArrayPrototypePush(dependencyJobs, jobPromise);
         const job = await jobPromise;