module: fix check for package.json at volume root

This patch converts the "read package scope" algorithm's while loop
into a do-while loop enabling items at the filesystem root dir to
be considered within the scope of a sibling package.json also at the
filesystem root dir.

Fixes: #33438

Co-authored-by: Guy Bedford <[email protected]>

PR-URL: #34595
Reviewed-By: Jan Krems <[email protected]>
Reviewed-By: Mary Marchini <[email protected]>

Author: Derek Lewis

doc/api/esm.md

@@ -1864,11 +1864,11 @@ _conditions_)
 
 > 1. Let _scopeURL_ be _url_.
 > 1. While _scopeURL_ is not the file system root,
+>    1. Set _scopeURL_ to the parent URL of _scopeURL_.
 >    1. If _scopeURL_ ends in a _"node_modules"_ path segment, return **null**.
 >    1. Let _pjson_ be the result of **READ_PACKAGE_JSON**(_scopeURL_).
 >    1. If _pjson_ is not **null**, then
 >       1. Return _pjson_.
->    1. Set _scopeURL_ to the parent URL of _scopeURL_.
 > 1. Return **null**.
 
 **READ_PACKAGE_JSON**(_packageURL_)

lib/internal/modules/cjs/loader.js

@@ -45,6 +45,9 @@ const {
   RegExpPrototypeTest,
   SafeMap,
   String,
+  StringPrototypeEndsWith,
+  StringPrototypeIndexOf,
+  StringPrototypeLastIndexOf,
   StringPrototypeMatch,
   StringPrototypeSlice,
   StringPrototypeStartsWith,
@@ -62,6 +65,7 @@ const assert = require('internal/assert');
 const fs = require('fs');
 const internalFS = require('internal/fs/utils');
 const path = require('path');
+const { sep } = path;
 const { emitWarningSync } = require('internal/process/warning');
 const { internalModuleStat } = internalBinding('fs');
 const packageJsonReader = require('internal/modules/package_json_reader');
@@ -282,20 +286,19 @@ function readPackage(requestPath) {
 }
 
 function readPackageScope(checkPath) {
-  const rootSeparatorIndex = checkPath.indexOf(path.sep);
+  const rootSeparatorIndex = StringPrototypeIndexOf(checkPath, sep);
   let separatorIndex;
-  while (
-    (separatorIndex = checkPath.lastIndexOf(path.sep)) > rootSeparatorIndex
-  ) {
-    checkPath = checkPath.slice(0, separatorIndex);
-    if (checkPath.endsWith(path.sep + 'node_modules'))
+  do {
+    separatorIndex = StringPrototypeLastIndexOf(checkPath, sep);
+    checkPath = StringPrototypeSlice(checkPath, 0, separatorIndex);
+    if (StringPrototypeEndsWith(checkPath, sep + 'node_modules'))
       return false;
-    const pjson = readPackage(checkPath);
+    const pjson = readPackage(checkPath + sep);
     if (pjson) return {
+      data: pjson,
       path: checkPath,
-      data: pjson
     };
-  }
+  } while (separatorIndex > rootSeparatorIndex);
   return false;
 }