From c2121228c95f9316076702681f4227cbff854abd Mon Sep 17 00:00:00 2001
From: Julien Elbaz <julien.elbaz@datadoghq.com>
Date: Mon, 5 May 2025 16:16:11 +0200
Subject: [PATCH 1/2] fix(rspack): prevent vfs concurrency issues

---
 src/rspack/index.ts | 12 +++++++++---
 src/types.ts        |  2 +-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/rspack/index.ts b/src/rspack/index.ts
index 662fac83..182fee39 100644
--- a/src/rspack/index.ts
+++ b/src/rspack/index.ts
@@ -56,7 +56,7 @@ export function getRspackPlugin<UserOptions = Record<string, never>>(
           if (plugin.resolveId) {
             const vfs = new FakeVirtualModulesPlugin(plugin)
             vfs.apply(compiler)
-            plugin.__vfsModules = new Set()
+            plugin.__vfsModules = new Map()
             plugin.__vfs = vfs as any
 
             compiler.hooks.compilation.tap(plugin.name, (compilation, { normalModuleFactory }) => {
@@ -105,8 +105,14 @@ export function getRspackPlugin<UserOptions = Record<string, never>>(
                 // we treat it as a virtual module
                 if (!fs.existsSync(resolved)) {
                   if (!plugin.__vfsModules!.has(resolved)) {
-                    plugin.__vfsModules!.add(resolved)
-                    await vfs.writeModule(resolved)
+                    const fsPromise = vfs.writeModule(resolved)
+                    plugin.__vfsModules!.set(resolved, fsPromise)
+                    await fsPromise
+                  }
+                  else {
+                    // Ensure that the module is written to the virtual file system
+                    // before we use it.
+                    await plugin.__vfsModules!.get(resolved)
                   }
                   resolved = encodeVirtualModuleId(resolved, plugin)
                 }
diff --git a/src/types.ts b/src/types.ts
index b178dcaa..a66b5983 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -147,7 +147,7 @@ export interface UnpluginOptions {
 export interface ResolvedUnpluginOptions extends UnpluginOptions {
   // injected internal objects
   __vfs?: VirtualModulesPlugin
-  __vfsModules?: Set<string>
+  __vfsModules?: Map<string, Promise<string>>
   __virtualModulePrefix: string
 }
 

From 0bd1252b43b3aeaa0d56fe44fe41bafae0228ccb Mon Sep 17 00:00:00 2001
From: Julien Elbaz <julien.elbaz@datadoghq.com>
Date: Mon, 5 May 2025 22:43:50 +0200
Subject: [PATCH 2/2] chore: typecheck

---
 src/webpack/index.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/webpack/index.ts b/src/webpack/index.ts
index 0454276c..14082aa5 100644
--- a/src/webpack/index.ts
+++ b/src/webpack/index.ts
@@ -54,7 +54,7 @@ export function getWebpackPlugin<UserOptions = Record<string, never>>(
               vfs = new VirtualModulesPlugin()
               compiler.options.plugins.push(vfs)
             }
-            plugin.__vfsModules = new Set()
+            plugin.__vfsModules = new Map()
             plugin.__vfs = vfs
 
             const resolverPlugin: ResolvePluginInstance = {
@@ -135,7 +135,7 @@ export function getWebpackPlugin<UserOptions = Record<string, never>>(
                       // https://github.com/unjs/unplugin/pull/155
                       if (!plugin.__vfsModules!.has(resolved)) {
                         plugin.__vfs!.writeModule(resolved, '')
-                        plugin.__vfsModules!.add(resolved)
+                        plugin.__vfsModules!.set(resolved, Promise.resolve(''))
                       }
                     }