module: simplify findPackageJSON implementation

PR-URL: #55543
Reviewed-By: Jacob Smith <jacob@frende.me>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>

lib/internal/modules/package_json_reader.js

@@ -7,7 +7,6 @@ const {
   RegExpPrototypeExec,
   StringPrototypeIndexOf,
   StringPrototypeSlice,
-  StringPrototypeStartsWith,
 } = primordials;
 const {
   fileURLToPath,
@@ -285,22 +284,14 @@ function findPackageJSON(specifier, base = 'data:') {
     validateString(specifier, 'specifier');
   }
 
-  let parentURL;
-  if (isURL(base)) {
-    parentURL = new URL(base);
-  } else {
+  let parentURL = base;
+  if (!isURL(base)) {
     validateString(base, 'base');
-    if (
-      path.isAbsolute(base) ||
-      (URLCanParse(base) && !StringPrototypeStartsWith(base, 'file:'))
-    ) {
-      parentURL = pathToFileURL(path.toNamespacedPath(base));
-    } else {
-      parentURL = URL.parse(base) || pathToFileURL(base);
-    }
+    parentURL = path.isAbsolute(base) ? pathToFileURL(base) : new URL(base);
   }
 
   if (specifier && specifier[0] !== '.' && specifier[0] !== '/' && !URLCanParse(specifier)) {
+    // If `specifier` is a bare specifier.
     const { packageJSONPath } = getPackageJSONURL(specifier, parentURL);
     return packageJSONPath;
   }