fix: separator issue for Windows

packages/pigment-css-vite-plugin/src/index.ts

@@ -9,6 +9,11 @@ import {
 } from '@pigment-css/react/utils';
 import { transformAsync } from '@babel/core';
 import baseWywPluginPlugin, { type VitePluginOptions } from './vite-plugin';
+import {
+  VIRTUAL_CSS_FILE,
+  VIRTUAL_THEME_FILE,
+  resolvePigmentPath,
+} from './utils/resolvePigmentPath';
 
 export interface PigmentOptions extends Omit<VitePluginOptions, 'themeArgs'> {
   /**
@@ -25,9 +30,6 @@ type PigmentMeta = {
   };
 };
 
-const VIRTUAL_CSS_FILE = `\0zero-runtime-styles.css`;
-const VIRTUAL_THEME_FILE = `\0zero-runtime-theme.js`;
-
 const extensions = ['.js', '.jsx', '.mjs', '.cjs', '.ts', '.tsx', '.mts', '.cts'];
 
 function hasCorectExtension(fileName: string) {
@@ -66,13 +68,8 @@ export function pigment(options: PigmentOptions) {
       name: 'pigment-css-theme-injection-plugin',
       enforce: 'pre',
       resolveId(source) {
-        if (finalTransformLibraries.some((lib) => source.includes(`${lib}/styles.css`))) {
-          return VIRTUAL_CSS_FILE;
-        }
-        if (finalTransformLibraries.some((lib) => source.includes(`${lib}/theme`))) {
-          return VIRTUAL_THEME_FILE;
-        }
-        return null;
+        // Vite/Rollup internally normalizes all path separators to forward slashes (/) before passing source to resolveId, regardless of the OS.
+        return resolvePigmentPath(source, allLibs);
       },
       load(id) {
         if (id === VIRTUAL_CSS_FILE) {

packages/pigment-css-vite-plugin/src/utils/resolvePigmentPath.ts

@@ -0,0 +1,26 @@
+/**
+ * Virtual CSS file path used for zero-runtime styles.
+ * @constant {string}
+ */
+export const VIRTUAL_CSS_FILE = `\0zero-runtime-styles.css`;
+/**
+ * Virtual theme module path used for zero-runtime theme.
+ * @constant {string}
+ */
+export const VIRTUAL_THEME_FILE = `\0zero-runtime-theme.js`;
+
+/**
+ * Resolves import paths to virtual modules for Pigment CSS artifacts.
+ * @param {string} source - Original import source path
+ * @param {string[]} allLibs - List of library names to match against
+ * @returns {string | null} Virtual module path if matched, otherwise null
+ */
+export function resolvePigmentPath(source: string, allLibs: string[]) {
+  if (allLibs.some((lib) => source.includes(`${lib}/styles.css`))) {
+    return VIRTUAL_CSS_FILE;
+  }
+  if (allLibs.some((lib) => source.includes(`${lib}/theme`))) {
+    return VIRTUAL_THEME_FILE;
+  }
+  return null;
+}

packages/pigment-css-vite-plugin/tests/utils/resolvePigmentPath.test.ts

@@ -0,0 +1,43 @@
+/* eslint-disable @typescript-eslint/no-unused-expressions */
+import { expect } from 'chai';
+import { resolvePigmentPath } from '../../src/utils/resolvePigmentPath';
+
+describe('processPigmentTheme', () => {
+  describe('resolvePigmentPath', () => {
+    it('should resolve pigment styles path in Unix env', () => {
+      const UnixSep = '/';
+      const source = '@mui/material-pigment-css/styles.css';
+      const allLibs = ['@mui/material-pigment-css', '@mui/material-other'];
+      const finalTransformLibraries = allLibs.map((lib) => lib.split('/').join(UnixSep));
+      // ✅ It works to resolve path in allLibs (Unix env)
+      expect(resolvePigmentPath(source, allLibs)).to.equal('\0zero-runtime-styles.css');
+      // ✅ It works to resolve path in finalTransformLibraries (Unix env)
+      expect(resolvePigmentPath(source, finalTransformLibraries)).to.equal(
+        '\0zero-runtime-styles.css',
+      );
+    });
+
+    it('should resolve pigment styles path in Windows env', () => {
+      const WindowsSep = '\\';
+      const source = '@mui/material-pigment-css/styles.css';
+      const allLibs = ['@mui/material-pigment-css', '@mui/material-other'];
+      const finalTransformLibraries = allLibs.map((lib) => lib.split('/').join(WindowsSep));
+      // ✅ It works to resolve path in allLibs (Windows env)
+      expect(resolvePigmentPath(source, allLibs)).to.equal('\0zero-runtime-styles.css');
+      // ❌ It doesn't work to resolve path in finalTransformLibraries (Windows env)
+      expect(resolvePigmentPath(source, finalTransformLibraries)).to.be.null;
+    });
+
+    it('should resolve pigment theme path', () => {
+      const source = '@mui/material-pigment-css/theme';
+      const allLibs = ['@mui/material-pigment-css', '@mui/material-other'];
+      expect(resolvePigmentPath(source, allLibs)).to.equal('\0zero-runtime-theme.js');
+    });
+
+    it('should not resolve other path', () => {
+      const source = '@mui/material-pigment-css-other/styles.css';
+      const allLibs = ['@mui/material-pigment-css', '@mui/material-other'];
+      expect(resolvePigmentPath(source, allLibs)).to.be.null;
+    });
+  });
+});