feat(vite): preserve vite sourcemaps for nitro build (#28521)

packages/vite/src/plugins/nitro-sourcemap.ts

@@ -0,0 +1,63 @@
+import { mkdir, readFile, writeFile } from 'node:fs/promises'
+import { dirname, resolve } from 'pathe'
+
+import type { Plugin as RollupPlugin } from 'rollup'
+import type { Plugin as VitePlugin } from 'vite'
+
+export const createSourcemapPreserver = () => {
+  let outputDir: string
+  const ids = new Set<string>()
+
+  const vitePlugin = {
+    name: 'nuxt:sourcemap-export',
+    configResolved (config) {
+      outputDir = config.build.outDir
+    },
+    async writeBundle (_options, bundle) {
+      for (const chunk of Object.values(bundle)) {
+        if (chunk.type !== 'chunk' || !chunk.map) { continue }
+
+        const id = resolve(outputDir, chunk.fileName)
+        ids.add(id)
+        const dest = id + '.map.json'
+        await mkdir(dirname(dest), { recursive: true })
+        await writeFile(dest, JSON.stringify({
+          file: chunk.map.file,
+          mappings: chunk.map.mappings,
+          names: chunk.map.names,
+          sources: chunk.map.sources,
+          sourcesContent: chunk.map.sourcesContent,
+          version: chunk.map.version,
+        }))
+      }
+    },
+  } satisfies VitePlugin
+
+  const nitroPlugin = {
+    name: 'nuxt:sourcemap-import',
+    async load (id) {
+      id = resolve(id)
+      if (!ids.has(id)) { return }
+
+      const [code, map] = await Promise.all([
+        readFile(id, 'utf-8').catch(() => undefined),
+        readFile(id + '.map.json', 'utf-8').catch(() => undefined),
+      ])
+
+      if (!code) {
+        this.warn('Failed loading file')
+        return null
+      }
+
+      return {
+        code,
+        map,
+      }
+    },
+  } satisfies RollupPlugin
+
+  return {
+    vitePlugin,
+    nitroPlugin,
+  }
+}

packages/vite/src/server.ts

@@ -5,11 +5,13 @@ import viteJsxPlugin from '@vitejs/plugin-vue-jsx'
 import { logger, resolvePath, tryResolveModule } from '@nuxt/kit'
 import { joinURL, withTrailingSlash, withoutLeadingSlash } from 'ufo'
 import type { ViteConfig } from '@nuxt/schema'
+import defu from 'defu'
 import type { ViteBuildContext } from './vite'
 import { createViteLogger } from './utils/logger'
 import { initViteNodeServer } from './vite-node'
 import { writeManifest } from './manifest'
 import { transpile } from './utils/transpile'
+import { createSourcemapPreserver } from './plugins/nitro-sourcemap'
 
 export async function buildServer (ctx: ViteBuildContext) {
   const helper = ctx.nuxt.options.nitro.imports !== false ? '' : 'globalThis.'
@@ -120,6 +122,17 @@ export async function buildServer (ctx: ViteBuildContext) {
     }
   }
 
+  // tell rollup's nitro build about the original sources of the generated vite server build
+  if (ctx.nuxt.options.sourcemap.server && !ctx.nuxt.options.dev) {
+    const { vitePlugin, nitroPlugin } = createSourcemapPreserver()
+    serverConfig.plugins!.push(vitePlugin)
+    ctx.nuxt.hook('nitro:build:before', (nitro) => {
+      nitro.options.rollupConfig = defu(nitro.options.rollupConfig, {
+        plugins: [nitroPlugin],
+      })
+    })
+  }
+
   serverConfig.customLogger = createViteLogger(serverConfig)
 
   await ctx.nuxt.callHook('vite:extendConfig', serverConfig, { isClient: false, isServer: true })