From de60f1e3d1eb03167362cf8ce0c6c4071430f812 Mon Sep 17 00:00:00 2001
From: Bjorn Lu <bjornlu.dev@gmail.com>
Date: Sun, 17 Mar 2024 23:25:48 +0800
Subject: [PATCH] perf(transformRequest): fast-path watch and sourcemap
 handling (#16170)

---
 packages/vite/src/node/server/sourcemap.ts    | 32 +++++++++++++++-
 .../vite/src/node/server/transformRequest.ts  | 37 +++++++------------
 2 files changed, 45 insertions(+), 24 deletions(-)

diff --git a/packages/vite/src/node/server/sourcemap.ts b/packages/vite/src/node/server/sourcemap.ts
index eafde8c25b67d1..a0ed31968b6c41 100644
--- a/packages/vite/src/node/server/sourcemap.ts
+++ b/packages/vite/src/node/server/sourcemap.ts
@@ -1,8 +1,9 @@
 import path from 'node:path'
 import fsp from 'node:fs/promises'
+import convertSourceMap from 'convert-source-map'
 import type { ExistingRawSourceMap, SourceMap } from 'rollup'
 import type { Logger } from '../logger'
-import { createDebugger } from '../utils'
+import { blankReplacer, createDebugger } from '../utils'
 
 const debug = createDebugger('vite:sourcemap', {
   onlyWhenFocused: true,
@@ -143,3 +144,32 @@ export function applySourcemapIgnoreList(
     if (!map.x_google_ignoreList) map.x_google_ignoreList = x_google_ignoreList
   }
 }
+
+export async function extractSourcemapFromFile(
+  code: string,
+  filePath: string,
+): Promise<{ code: string; map: SourceMap } | undefined> {
+  const map = (
+    convertSourceMap.fromSource(code) ||
+    (await convertSourceMap.fromMapFileSource(
+      code,
+      createConvertSourceMapReadMap(filePath),
+    ))
+  )?.toObject()
+
+  if (map) {
+    return {
+      code: code.replace(convertSourceMap.mapFileCommentRegex, blankReplacer),
+      map,
+    }
+  }
+}
+
+function createConvertSourceMapReadMap(originalFileName: string) {
+  return (filename: string) => {
+    return fsp.readFile(
+      path.resolve(path.dirname(originalFileName), filename),
+      'utf-8',
+    )
+  }
+}
diff --git a/packages/vite/src/node/server/transformRequest.ts b/packages/vite/src/node/server/transformRequest.ts
index 8341f14a70a737..5dc6e3921215af 100644
--- a/packages/vite/src/node/server/transformRequest.ts
+++ b/packages/vite/src/node/server/transformRequest.ts
@@ -2,14 +2,12 @@ import fsp from 'node:fs/promises'
 import path from 'node:path'
 import { performance } from 'node:perf_hooks'
 import getEtag from 'etag'
-import convertSourceMap from 'convert-source-map'
 import MagicString from 'magic-string'
 import { init, parse as parseImports } from 'es-module-lexer'
 import type { PartialResolvedId, SourceDescription, SourceMap } from 'rollup'
 import colors from 'picocolors'
 import type { ModuleNode, ViteDevServer } from '..'
 import {
-  blankReplacer,
   createDebugger,
   ensureWatchedFile,
   injectQuery,
@@ -24,7 +22,11 @@ import { checkPublicFile } from '../publicDir'
 import { isDepsOptimizerEnabled } from '../config'
 import { getDepsOptimizer, initDevSsrDepsOptimizer } from '../optimizer'
 import { cleanUrl, unwrapId } from '../../shared/utils'
-import { applySourcemapIgnoreList, injectSourcesContent } from './sourcemap'
+import {
+  applySourcemapIgnoreList,
+  extractSourcemapFromFile,
+  injectSourcesContent,
+} from './sourcemap'
 import { isFileServingAllowed } from './middlewares/static'
 import { throwClosedServerError } from './pluginContainer'
 
@@ -263,21 +265,19 @@ async function loadAndTransform(
           throw e
         }
       }
-      ensureWatchedFile(server.watcher, file, config.root)
+      if (code != null) {
+        ensureWatchedFile(server.watcher, file, config.root)
+      }
     }
     if (code) {
       try {
-        map = (
-          convertSourceMap.fromSource(code) ||
-          (await convertSourceMap.fromMapFileSource(
-            code,
-            createConvertSourceMapReadMap(file),
-          ))
-        )?.toObject()
-
-        code = code.replace(convertSourceMap.mapFileCommentRegex, blankReplacer)
+        const extracted = await extractSourcemapFromFile(code, file)
+        if (extracted) {
+          code = extracted.code
+          map = extracted.map
+        }
       } catch (e) {
-        logger.warn(`Failed to load source map for ${url}.`, {
+        logger.warn(`Failed to load source map for ${file}.\n${e}`, {
           timestamp: true,
         })
       }
@@ -406,15 +406,6 @@ async function loadAndTransform(
   return result
 }
 
-function createConvertSourceMapReadMap(originalFileName: string) {
-  return (filename: string) => {
-    return fsp.readFile(
-      path.resolve(path.dirname(originalFileName), filename),
-      'utf-8',
-    )
-  }
-}
-
 /**
  * When a module is soft-invalidated, we can preserve its previous `transformResult` and
  * return similar code to before: