Ensure entry tracing applies for app correctly (vercel#41140)

This ensures we properly detect and trace `app` dir entries and adds a
regression test to ensure this is working as expected.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

packages/next/build/webpack-config.ts

@@ -1817,8 +1817,8 @@ export default async function getBaseWebpackConfig(
           {
             appDir: dir,
             esmExternals: config.experimental.esmExternals,
-            staticImageImports: !config.images.disableStaticImages,
             outputFileTracingRoot: config.experimental.outputFileTracingRoot,
+            appDirEnabled: !!config.experimental.appDir,
           }
         ),
       // Moment.js is an extremely popular library that bundles large locale files

packages/next/build/webpack/plugins/next-trace-entrypoints-plugin.ts

@@ -24,7 +24,7 @@ const TRACE_IGNORES = [
 function getModuleFromDependency(
   compilation: any,
   dep: any
-): webpack.Module & { resource?: string } {
+): webpack.Module & { resource?: string; request?: string } {
   return compilation.moduleGraph.getModule(dep)
 }
 
@@ -84,30 +84,30 @@ function getFilesMapFromReasons(
 
 export class TraceEntryPointsPlugin implements webpack.WebpackPluginInstance {
   private appDir: string
+  private appDirEnabled?: boolean
   private tracingRoot: string
   private entryTraces: Map<string, Set<string>>
   private excludeFiles: string[]
   private esmExternals?: NextConfigComplete['experimental']['esmExternals']
-  private staticImageImports?: boolean
 
   constructor({
     appDir,
+    appDirEnabled,
     excludeFiles,
     esmExternals,
-    staticImageImports,
     outputFileTracingRoot,
   }: {
     appDir: string
+    appDirEnabled?: boolean
     excludeFiles?: string[]
-    staticImageImports: boolean
     outputFileTracingRoot?: string
     esmExternals?: NextConfigComplete['experimental']['esmExternals']
   }) {
     this.appDir = appDir
     this.entryTraces = new Map()
     this.esmExternals = esmExternals
+    this.appDirEnabled = appDirEnabled
     this.excludeFiles = excludeFiles || []
-    this.staticImageImports = staticImageImports
     this.tracingRoot = outputFileTracingRoot || appDir
   }
 
@@ -257,15 +257,44 @@ export class TraceEntryPointsPlugin implements webpack.WebpackPluginInstance {
 
             finishModulesSpan.traceChild('get-entries').traceFn(() => {
               compilation.entries.forEach((entry, name) => {
-                if (name?.replace(/\\/g, '/').startsWith('pages/')) {
+                const normalizedName = name?.replace(/\\/g, '/')
+
+                const isPage = normalizedName.startsWith('pages/')
+                const isApp =
+                  this.appDirEnabled && normalizedName.startsWith('app/')
+
+                if (isApp || isPage) {
                   for (const dep of entry.dependencies) {
                     if (!dep) continue
                     const entryMod = getModuleFromDependency(compilation, dep)
 
+                    // since app entries are wrapped in next-app-loader
+                    // we need to pull the original pagePath for
+                    // referencing during tracing
+                    if (isApp && entryMod.request) {
+                      const loaderQueryIdx = entryMod.request.indexOf('?')
+
+                      const loaderQuery = new URLSearchParams(
+                        entryMod.request.substring(loaderQueryIdx)
+                      )
+                      const resource =
+                        loaderQuery
+                          .get('pagePath')
+                          ?.replace(
+                            'private-next-app-dir',
+                            nodePath.join(this.appDir, 'app')
+                          ) || ''
+
+                      entryModMap.set(resource, entryMod)
+                      entryNameMap.set(resource, name)
+                    }
+
                     if (entryMod && entryMod.resource) {
-                      if (
-                        entryMod.resource.replace(/\\/g, '/').includes('pages/')
-                      ) {
+                      const normalizedResource = entryMod.resource.replace(
+                        /\\/g,
+                        '/'
+                      )
+                      if (normalizedResource.includes('pages/')) {
                         entryNameMap.set(entryMod.resource, name)
                         entryModMap.set(entryMod.resource, entryMod)
                       } else {

test/e2e/app-dir/app/app/dashboard/deployments/[id]/data.json

@@ -0,0 +1,3 @@
+{
+  "hello": "world"
+}

test/e2e/app-dir/app/app/dashboard/deployments/[id]/page.js

@@ -1,6 +1,15 @@
 import { experimental_use as use } from 'react'
+import fs from 'fs'
+import path from 'path'
 
 async function getData({ params }) {
+  const data = JSON.parse(
+    fs.readFileSync(
+      path.join(process.cwd(), 'app/dashboard/deployments/[id]/data.json')
+    )
+  )
+  console.log('data.json', data)
+
   return {
     id: params.id,
   }

test/e2e/app-dir/index.test.ts

@@ -35,6 +35,19 @@ describe('app dir', () => {
     })
     afterAll(() => next.destroy())
 
+    if ((global as any).isNextStart) {
+      it('should generate build traces correctly', async () => {
+        const trace = JSON.parse(
+          await next.readFile(
+            '.next/server/app/dashboard/deployments/[id]/page.js.nft.json'
+          )
+        ) as { files: string[] }
+        expect(trace.files.some((file) => file.endsWith('data.json'))).toBe(
+          true
+        )
+      })
+    }
+
     it('should use application/octet-stream for flight', async () => {
       const res = await fetchViaHTTP(
         next.url,