bug: Inconsistent path separator in resolveId() on Windows

[maxpatiiuk]

Describe the bug

In most places Vite is using POSIX path separators even on Windows (i.e in config.root, file identifiers and etc).

However, there is one place where this is inconsistent and platform path separators are used:

If build.lib.entry includes a virtual file, the resolveId() hook in plugins will be called:

  build: {
    lib: {
      formats: ["es"],
      entry: "virtual-file.js",
    },
  },

The resolveId() is called with an absolute path (process.cwd() + '/virtual-file.js') that uses the platform's path separator (\ on Windows), rather than POSIX path separator

This is inconsistent behavior and lead to a bug in my plugin on Windows.

Reproduction

https://github.com/maxpatiiuk/vite-inconsistent-resolve-id

Steps to reproduce

1. Use Windows machine

2. Clone the reproduction repository

   git clone https://github.com/maxpatiiuk/vite-inconsistent-resolve-id

3. Install dependencies

   npm install

4. Run build

   npx vite build
   

5. See build output show a message like
   resolveId called with C:\Users\root\... rather than
   resolveId called with C:/Users/root/...

System Info

System:
    OS: Windows 10 10.0.19045
    CPU: (2) x64 Intel(R) Xeon(R) Gold 6342 CPU @ 2.80GHz
    Memory: 3.27 GB / 7.50 GB
  Binaries:
    Node: 20.14.0 - C:\Program Files\nodejs\node.EXE     
    npm: 10.7.0 - C:\Program Files\nodejs\npm.CMD        
  Browsers:
    Edge: Chromium (126.0.2592.102)
    Internet Explorer: 11.0.19041.4355

Used Package Manager

npm

Logs

Click to expand!

  vite:config bundled config file loaded in 173.20ms +0ms
  vite:config using resolved config: {
  vite:config   build: {
  vite:config     target: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],   
  vite:config     cssTarget: [ 'es2020', 'edge88', 'firefox78', 'chrome87', 'safari14' ],
  vite:config     outDir: 'dist',
  vite:config     assetsDir: 'assets',
  vite:config     assetsInlineLimit: 4096,
  vite:config     cssCodeSplit: false,
  vite:config     sourcemap: false,
  vite:config     rollupOptions: {},
  vite:config     minify: 'esbuild',
  vite:config     terserOptions: {},
  vite:config     write: true,
  vite:config     emptyOutDir: null,
  vite:config     copyPublicDir: true,
  vite:config     manifest: false,
  vite:config     lib: { formats: [Array], entry: 'virtual-file.js' },
  vite:config     ssr: false,
  vite:config     ssrManifest: false,
  vite:config     ssrEmitAssets: false,
  vite:config     reportCompressedSize: true,
  vite:config     chunkSizeWarningLimit: 500,
  vite:config     watch: null,
  vite:config     commonjsOptions: { include: [Array], extensions: [Array] },
  vite:config     dynamicImportVarsOptions: { warnOnError: true, exclude: [Array] },
  vite:config     modulePreload: { polyfill: true },
  vite:config     cssMinify: true
  vite:config   },
  vite:config   plugins: [
  vite:config     'vite:build-metadata',
  vite:config     'vite:watch-package-data',
  vite:config     'vite:pre-alias',
  vite:config     'alias',
  vite:config     'vite:modulepreload-polyfill',
  vite:config     'vite:resolve',
  vite:config     'vite:html-inline-proxy',
  vite:config     'vite:css',
  vite:config     'vite:esbuild',
  vite:config     'vite:json',
  vite:config     'vite:wasm-helper',
  vite:config     'vite:worker',
  vite:config     'vite:asset',
  vite:config     'resolve-id',
  vite:config     'vite:wasm-fallback',
  vite:config     'vite:define',
  vite:config     'vite:css-post',
  vite:config     'vite:build-html',
  vite:config     'vite:worker-import-meta-url',
  vite:config     'vite:asset-import-meta-url',
  vite:config     'vite:force-systemjs-wrap-complete',
  vite:config     'commonjs',
  vite:config     'vite:data-uri',
  vite:config     'vite:dynamic-import-vars',
  vite:config     'vite:import-glob',
  vite:config     'vite:build-import-analysis',
  vite:config     'vite:esbuild-transpile',
  vite:config     'vite:terser',
  vite:config     'vite:reporter',
  vite:config     'vite:load-fallback'
  vite:config   ],
  vite:config   configFile: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id/vite.config.ts',
  vite:config   configFileDependencies: [
  vite:config     'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id/vite.config.ts'
  vite:config   ],
  vite:config   inlineConfig: {
  vite:config     root: undefined,
  vite:config     base: undefined,
  vite:config     mode: undefined,
  vite:config     configFile: undefined,
  vite:config     logLevel: undefined,
  vite:config     clearScreen: undefined,
  vite:config     build: {}
  vite:config   },
  vite:config   root: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id',
  vite:config   base: '/',
  vite:config   rawBase: '/',
  vite:config   resolve: {
  vite:config     mainFields: [ 'browser', 'module', 'jsnext:main', 'jsnext' ],
  vite:config     conditions: [],
  vite:config     extensions: [
  vite:config       '.mjs',  '.js',
  vite:config       '.mts',  '.ts',
  vite:config       '.jsx',  '.tsx',
  vite:config       '.json'
  vite:config     ],
  vite:config     dedupe: [],
  vite:config     preserveSymlinks: false,
  vite:config     alias: [ [Object], [Object] ]
  vite:config   },
  vite:config   publicDir: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id/public',
  vite:config   cacheDir: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id/node_modules/.vite',
  vite:config   command: 'build',
  vite:config   mode: 'production',
  vite:config   ssr: {
  vite:config     target: 'node',
  vite:config     optimizeDeps: { noDiscovery: true, esbuildOptions: [Object] }
  vite:config   },
  vite:config   isWorker: false,
  vite:config   mainConfig: null,
  vite:config   bundleChain: [],
  vite:config   isProduction: true,
  vite:config   css: { lightningcss: undefined },
  vite:config   esbuild: { jsxDev: false },
  vite:config   server: {
  vite:config     preTransformRequests: true,
  vite:config     sourcemapIgnoreList: [Function: isInNodeModules$1],
  vite:config     middlewareMode: false,
  vite:config     fs: {
  vite:config       strict: true,
  vite:config       allow: [Array],
  vite:config       deny: [Array],
  vite:config       cachedChecks: undefined
  vite:config     }
  vite:config   },
  vite:config   preview: {
  vite:config     port: undefined,
  vite:config     strictPort: undefined,
  vite:config     host: undefined,
  vite:config     https: undefined,
  vite:config     open: undefined,
  vite:config     proxy: undefined,
  vite:config     cors: undefined,
  vite:config     headers: undefined
  vite:config   },
  vite:config   envDir: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id',
  vite:config   env: { BASE_URL: '/', MODE: 'production', DEV: false, PROD: true },
  vite:config   assetsInclude: [Function: assetsInclude],
  vite:config   logger: {
  vite:config     hasWarned: false,
  vite:config     info: [Function: info],
  vite:config     warn: [Function: warn],
  vite:config     warnOnce: [Function: warnOnce],
  vite:config     error: [Function: error],
  vite:config     clearScreen: [Function: clearScreen],
  vite:config     hasErrorLogged: [Function: hasErrorLogged]
  vite:config   },
  vite:config   packageCache: Map(1) {
  vite:config     'fnpd_C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id' => {
  vite:config       dir: 'C:/Users/mak13180/Documents/arcgis-web-components/packages/test-packages/vite-inconsistent-resolve-id',
  vite:config       data: [Object],
  vite:config       hasSideEffects: [Function: hasSideEffects],
  vite:config       webResolvedImports: {},
  vite:config       nodeResolvedImports: {},
  vite:config       setResolvedCache: [Function: setResolvedCache],
  vite:config       getResolvedCache: [Function: getResolvedCache]
  vite:config     },
  vite:config     set: [Function (anonymous)]
  vite:config   },
  vite:config   createResolver: [Function: createResolver],
  vite:config   optimizeDeps: {
  vite:config     holdUntilCrawlEnd: true,
  vite:config     esbuildOptions: { preserveSymlinks: false }
  vite:config   },
  vite:config   worker: { format: 'iife', plugins: '() => plugins', rollupOptions: {} },
  vite:config   appType: 'spa',
  vite:config   experimental: { importGlobRestoreExtension: false, hmrPartialAccept: false },
  vite:config   getSortedPlugins: [Function: getSortedPlugins],
  vite:config   getSortedPluginHooks: [Function: getSortedPluginHooks]
  vite:config } +57ms
vite v5.3.1 building for production...
resolveId called with:  C:\Users\mak13180\Documents\arcgis-web-components\packages\test-packages\vite-inconsistent-resolve-id\virtual-file.js
✓ 1 modules transformed.
dist/vite-project.js  0.03 kB │ gzip: 0.05 kB
✓ built in 285ms

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[bluwy]

I'm not sure this is exactly a bug. In the resolveId hook, the given id isn't guaranteed to be normalized (the term used by Vite for forward slash only paths), what Vite guarantees within its plugins and encourages others plugins to do so, is that resolved ids (returned from resolveId hook) are normalized.

Non-normalized path can also happen if user writes imports like import "foo\\bar" or import "C:\\foo\\bar", which they will be passed to resolveId as is.

Your plugin should be updated in this case to handle backslashes.