fix: the ASCII whitespaces are preserved so can not be escaped

.cspell.json

@@ -50,6 +50,7 @@
     "**/fonts/**",
     "node_modules",
     "coverage",
-    "*.log"
+    "*.log",
+    "test/outputs"
   ]
 }

src/utils.js

@@ -259,8 +259,10 @@ function normalizePath(file) {
   return path.sep === "\\" ? file.replace(/\\/g, "/") : file;
 }
 
+const reversedCharMapper = {};
+
 // eslint-disable-next-line no-control-regex
-const filenameReservedRegex = /[<>:"/\\|?*]/g;
+const filenameReservedRegex = /([<>:"/\\|?*\s])/g;
 // eslint-disable-next-line no-control-regex
 const reControlChars = /[\u0000-\u001f\u0080-\u009f]/g;
 
@@ -270,7 +272,21 @@ function escapeLocalIdent(localident) {
     localident
       // For `[hash]` placeholder
       .replace(/^((-?[0-9])|--)/, "_$1")
-      .replace(filenameReservedRegex, "-")
+      .replace(filenameReservedRegex, (_, $1) => {
+        // normalize Windows path `\` as unix `/` for constancy
+        const char = $1 === "\\" ? "/" : $1;
+
+        if (reversedCharMapper[char]) {
+          return reversedCharMapper[char];
+        }
+
+        const hex = char.charCodeAt(0).toString(16).toUpperCase();
+        const escaped = `\\C${hex}`;
+
+        reversedCharMapper[char] = escaped;
+
+        return escaped;
+      })
       .replace(reControlChars, "-")
       .replace(/\./g, "-"),
   );

test/__snapshots__/import-option.test.js.snap

@@ -1,4 +1,4 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
 
 exports[`"import" option should jeep order of imports with 'webpackIgnore': errors 1`] = `[]`;