esm: Fix linting errors and test coverage

Remove importParents guard.
Use primordials instead.

Author: mattskel

lib/internal/modules/esm/loader.js

@@ -10,6 +10,7 @@ const {
   Promise,
   PromisePrototypeThen,
   RegExpPrototypeSymbolReplace,
+  SafeMap,
   encodeURIComponent,
   hardenRegExp,
 } = primordials;
@@ -195,7 +196,7 @@ class ModuleLoader {
 
   constructor(asyncLoaderHooks) {
     this.#setAsyncLoaderHooks(asyncLoaderHooks);
-    this.importParents = new Map();
+    this.importParents = new SafeMap();
   }
 
   /**

lib/internal/modules/esm/module_job.js

@@ -24,25 +24,28 @@ let debug = require('internal/util/debuglog').debuglog('esm', (fn) => {
 });
 
 const {
-  overrideStackTrace,
   ErrorPrepareStackTrace,
-  codes,
+  codes: {
+    ERR_REQUIRE_ASYNC_MODULE,
+  },
+  overrideStackTrace,
 } = require('internal/errors');
 
-const { ERR_REQUIRE_ASYNC_MODULE } = codes;
-
 /**
  * Builds a linear import trace by walking parent modules
  * from the module that threw during evaluation.
+ * @returns {Array<{child: string, parent: string}>|null}
  */
 function buildImportTrace(importParents, startURL) {
   const trace = [];
   let current = startURL;
-  const seen = new Set([current]);
+  const seen = new SafeSet([current]);
 
   while (true) {
     const parent = importParents.get(current);
-    if (!parent || seen.has(parent)) break;
+    if (!parent || seen.has(parent)) {
+      break;
+    }
 
     trace.push({ child: current, parent });
     seen.add(current);
@@ -54,6 +57,7 @@ function buildImportTrace(importParents, startURL) {
 
 /**
  * Formats an import trace for inclusion in an error stack.
+ * @returns {string}
  */
 function formatImportTrace(trace) {
   return trace
@@ -62,12 +66,13 @@ function formatImportTrace(trace) {
 }
 
 /**
- * Appends an ESM import trace to an error’s stack output.
+ * Appends an ESM import trace to an error's stack output.
  * Uses a per-error stack override; no global side effects.
  */
 function decorateErrorWithImportTrace(e, importParents) {
-   if (!importParents || typeof importParents.get !== 'function') return;
-  if (!e || typeof e !== 'object') return;
+  if (!e || typeof e !== 'object') {
+    return;
+  }
 
   overrideStackTrace.set(e, (error, trace) => {
     let thrownURL;
@@ -84,7 +89,9 @@ function decorateErrorWithImportTrace(e, importParents) {
 
     const importTrace = thrownURL ? buildImportTrace(importParents, thrownURL) : null;
     const stack = ErrorPrepareStackTrace(error, trace);
-    if (!importTrace) return stack;
+    if (!importTrace) {
+      return stack;
+    }
 
     return `${stack}\n\nImport trace:\n${formatImportTrace(importTrace)}`;
   });