refactor: improve main module loading resolution

Instead of rewritting main files we simply add some logic in then loader -- cf:
nodejs/node#41465

A la tchusss abomination

components/.ordering

@@ -59,6 +59,5 @@ receptor
 batch
 questionnaire
 setup
-abomination
 init
 status

components/configuration-accessor/default/index.mjs

@@ -231,12 +231,6 @@ export const compileConfigurationCommand = (configuration, env) => {
       ...env,
       NODE_OPTIONS: [
         coalesce(env, "NODE_OPTIONS", ""),
-        // abomination: https://github.com/mochajs/mocha/issues/4720
-        `--require=${pathifyURL(
-          appendURLSegmentArray(directory, ["lib", "node", "abomination.js"]),
-          base,
-          true,
-        )}`,
         `--experimental-loader=${generateEscape(exec)(
           pathifyURL(
             appendURLSegmentArray(directory, [

components/configuration-accessor/default/index.test.mjs

@@ -315,7 +315,6 @@ assertDeepEqual(
     env: {
       NODE_OPTIONS: [
         "--node-key=node-value",
-        "--require=../agent/lib/node/abomination.js",
         "--experimental-loader=../agent/lib/node/recorder-process.mjs",
       ].join(" "),
       VAR1: "VAL1",
@@ -400,7 +399,6 @@ assertDeepEqual(
         env: {
           NODE_OPTIONS: [
             "",
-            "--require=../agent/lib/node/abomination.js",
             "--experimental-loader=../agent/lib/node/mocha-loader.mjs",
           ].join(" "),
         },

lib/node/loader.mjs

@@ -1,4 +1,5 @@
 const {
+  process: { stdout },
   Error,
   undefined,
   parseInt,
@@ -18,9 +19,30 @@ const parseMajorVersion = (version) => {
   }
 };
 
+let is_main = true;
+
+const message =
+  "Treating main file as commonjs, this might not always be appropriate -- cf: https://github.com/nodejs/node/issues/41465\n";
+
 export default (node_version, esm_hook_variable) => {
   const major_node_version = parseMajorVersion(node_version);
   return {
+    getFormat:
+      major_node_version >= 16
+        ? undefined
+        : (url, context, next) => {
+            if (is_main) {
+              is_main = false;
+              try {
+                return next(url, context, next);
+              } catch {
+                stdout.write(message);
+                return { format: "commonjs" };
+              }
+            } else {
+              return next(url, context, next);
+            }
+          },
     transformSource:
       major_node_version >= 16
         ? undefined
@@ -39,6 +61,13 @@ export default (node_version, esm_hook_variable) => {
       major_node_version < 16
         ? undefined
         : (url, context, next) => {
+            if (is_main) {
+              is_main = false;
+              if (context.format === undefined) {
+                stdout.write(message);
+                context.format = "commonjs";
+              }
+            }
             if (hasOwn(globalThis, esm_hook_variable)) {
               return globalThis[esm_hook_variable].load(url, context, next);
             } else {

lib/node/mocha-loader.mjs

@@ -6,7 +6,7 @@ import Mocha from "mocha";
 import Loader from "./loader.mjs";
 
 import { params, configuration } from "./configuration.mjs";
-export const { transformSource, load } = Loader(
+export const { getFormat, transformSource, load } = Loader(
   version,
   configuration.hooks.esm,
 );

lib/node/recorder-process.mjs

@@ -6,7 +6,7 @@ const {
 import Loader from "./loader.mjs";
 import { configuration, params } from "./configuration.mjs";
 
-export const { transformSource, load } = Loader(
+export const { getFormat, transformSource, load } = Loader(
   version,
   configuration.hooks.esm,
 );

lib/node/recorder-remote.mjs

@@ -6,7 +6,7 @@ const {
 import Loader from "./loader.mjs";
 import { configuration, params } from "./configuration.mjs";
 
-export const { transformSource, load } = Loader(
+export const { getFormat, transformSource, load } = Loader(
   version,
   configuration.hooks.esm,
 );