fix(vite-node): remove fake first line mapping on Vite 6 (#7124)

Author: hi-ogawa

package.json

@@ -62,7 +62,7 @@
     "tinyglobby": "^0.2.10",
     "tsx": "^4.19.2",
     "typescript": "^5.7.3",
-    "vite": "^5.4.0",
+    "vite": "^6.0.11",
     "vitest": "workspace:*",
     "zx": "^8.3.0"
   },

packages/vite-node/src/server.ts

@@ -12,6 +12,7 @@ import { performance } from 'node:perf_hooks'
 import { pathToFileURL } from 'node:url'
 import createDebug from 'debug'
 import { join, normalize, relative, resolve } from 'pathe'
+import { version as viteVersion } from 'vite'
 import { Debugger } from './debug'
 import { shouldExternalize } from './externalize'
 import { withInlineSourcemap } from './source-map'
@@ -392,6 +393,7 @@ export class ViteNodeServer {
     return withInlineSourcemap(result, {
       filepath: mod?.file || filepath,
       root: this.server.config.root,
+      noFirstLineMapping: Number(viteVersion.split('.')[0]) >= 6,
     })
   }
 

packages/vite-node/src/source-map.ts

@@ -22,6 +22,7 @@ export function withInlineSourcemap(
   options: {
     root: string // project root path of this resource
     filepath: string
+    noFirstLineMapping?: boolean
   },
 ) {
   const map = result.map
@@ -63,7 +64,9 @@ export function withInlineSourcemap(
 
   // If the first line is not present on source maps, add simple 1:1 mapping ([0,0,0,0], [1,0,0,0])
   // so that debuggers can be set to break on first line
-  if (map.mappings.startsWith(';')) {
+  // Since Vite 6, import statements at the top of the file are preserved correctly,
+  // so we don't need to add this mapping anymore.
+  if (!options.noFirstLineMapping && map.mappings.startsWith(';')) {
     map.mappings = `AAAA,CAAA${map.mappings}`
   }