fix: read the correct package.json in ssrExternal (#5927)

Fixes #5890

packages/vite/src/node/ssr/ssrExternal.ts

@@ -8,7 +8,7 @@ import {
   normalizePath,
   resolveFrom
 } from '../utils'
-import { ResolvedConfig } from '..'
+import { Logger, ResolvedConfig } from '..'
 import { createFilter } from '@rollup/pluginutils'
 
 const debug = createDebugger('vite:ssr-external')
@@ -37,7 +37,8 @@ export function resolveSSRExternal(
     config.root,
     config.resolve.preserveSymlinks,
     ssrExternals,
-    seen
+    seen,
+    config.logger
   )
 
   const importedDeps = knownImports.map(getNpmPackageName).filter(isDefined)
@@ -68,17 +69,18 @@ function collectExternals(
   root: string,
   preserveSymlinks: boolean | undefined,
   ssrExternals: Set<string>,
-  seen: Set<string>
+  seen: Set<string>,
+  logger: Logger
 ) {
-  const pkgContent = lookupFile(root, ['package.json'])
-  if (!pkgContent) {
+  const rootPkgContent = lookupFile(root, ['package.json'])
+  if (!rootPkgContent) {
     return
   }
 
-  const pkg = JSON.parse(pkgContent)
+  const rootPkg = JSON.parse(rootPkgContent)
   const deps = {
-    ...pkg.devDependencies,
-    ...pkg.dependencies
+    ...rootPkg.devDependencies,
+    ...rootPkg.dependencies
   }
 
   const resolveOptions: InternalResolveOptions = {
@@ -141,6 +143,14 @@ function collectExternals(
     // or are there others like SystemJS / AMD that we'd need to handle?
     // for now, we'll just leave this as is
     else if (/\.m?js$/.test(esmEntry)) {
+      const pkgPath = resolveFrom(`${id}/package.json`, root)
+      const pkgContent = fs.readFileSync(pkgPath, 'utf-8')
+
+      if (!pkgContent) {
+        continue
+      }
+      const pkg = JSON.parse(pkgContent)
+
       if (pkg.type === 'module' || esmEntry.endsWith('.mjs')) {
         ssrExternals.add(id)
         continue
@@ -149,12 +159,17 @@ function collectExternals(
       const content = fs.readFileSync(esmEntry, 'utf-8')
       if (/\bmodule\.exports\b|\bexports[.\[]|\brequire\s*\(/.test(content)) {
         ssrExternals.add(id)
+        continue
       }
+
+      logger.warn(
+        `${id} is incorrectly packaged. Please contact the package author to fix.`
+      )
     }
   }
 
   for (const depRoot of depsToTrace) {
-    collectExternals(depRoot, preserveSymlinks, ssrExternals, seen)
+    collectExternals(depRoot, preserveSymlinks, ssrExternals, seen, logger)
   }
 }