fix: apply type: module only to runtime modules

src/build/content/server.ts

@@ -262,7 +262,7 @@ export const copyNextDependencies = async (ctx: PluginContext): Promise<void> =>
     const promises: Promise<void>[] = entries.map(async (entry) => {
       // copy all except the package.json and distDir (.next) folder as this is handled in a separate function
       // this will include the node_modules folder as well
-      if (entry === 'package.json' || entry === ctx.nextDistDir) {
+      if (entry === ctx.nextDistDir) {
         return
       }
       const src = join(ctx.standaloneDir, entry)

src/build/functions/server.ts

@@ -53,11 +53,20 @@ const copyHandlerDependencies = async (ctx: PluginContext) => {
       )
     }
 
+    // We need to create a package.json file with type: module to make sure that the runtime modules
+    // are handled correctly as ESM modules
+    promises.push(
+      writeFile(
+        join(ctx.serverHandlerRuntimeModulesDir, 'package.json'),
+        JSON.stringify({ type: 'module' }),
+      ),
+    )
+
     const fileList = await glob('dist/**/*', { cwd: ctx.pluginDir })
 
     for (const filePath of fileList) {
       promises.push(
-        cp(join(ctx.pluginDir, filePath), join(ctx.serverHandlerDir, '.netlify', filePath), {
+        cp(join(ctx.pluginDir, filePath), join(ctx.serverHandlerRuntimeModulesDir, filePath), {
           recursive: true,
           force: true,
         }),
@@ -85,13 +94,6 @@ const writeHandlerManifest = async (ctx: PluginContext) => {
   )
 }
 
-const writePackageMetadata = async (ctx: PluginContext) => {
-  await writeFile(
-    join(ctx.serverHandlerRootDir, 'package.json'),
-    JSON.stringify({ type: 'module' }),
-  )
-}
-
 const applyTemplateVariables = (template: string, variables: Record<string, string>) => {
   return Object.entries(variables).reduce((acc, [key, value]) => {
     return acc.replaceAll(key, value)
@@ -136,13 +138,12 @@ export const clearStaleServerHandlers = async (ctx: PluginContext) => {
  */
 export const createServerHandler = async (ctx: PluginContext) => {
   await tracer.withActiveSpan('createServerHandler', async () => {
-    await mkdir(join(ctx.serverHandlerDir, '.netlify'), { recursive: true })
+    await mkdir(join(ctx.serverHandlerRuntimeModulesDir), { recursive: true })
 
     await copyNextServerCode(ctx)
     await copyNextDependencies(ctx)
     await copyHandlerDependencies(ctx)
     await writeHandlerManifest(ctx)
-    await writePackageMetadata(ctx)
     await writeHandlerFile(ctx)
 
     await verifyHandlerDirStructure(ctx)

src/build/plugin-context.ts

@@ -182,6 +182,10 @@ export class PluginContext {
     return join(this.serverHandlerRootDir, this.distDirParent)
   }
 
+  get serverHandlerRuntimeModulesDir(): string {
+    return join(this.serverHandlerDir, '.netlify')
+  }
+
   get nextServerHandler(): string {
     if (this.relativeAppDir.length !== 0) {
       return join(this.lambdaWorkingDirectory, '.netlify/dist/run/handlers/server.js')