Actually externalize optional deps

Author: davidmyersdev

src/index.ts

@@ -1,5 +1,5 @@
-import { existsSync, readFileSync } from 'fs'
-import { join } from 'path'
+import { existsSync, readFileSync } from 'node:fs'
+import { join } from 'node:path'
 import type { Plugin } from 'vite'
 
 interface UserOptions {
@@ -9,6 +9,10 @@ interface UserOptions {
   useFile: string,
 }
 
+const parseFile = (file: string) => {
+  return JSON.parse(readFileSync(file).toString())
+}
+
 export const externalizeDeps = (options: Partial<UserOptions> = {}): Plugin => {
   const optionsResolved: UserOptions = {
     deps: true,
@@ -24,7 +28,7 @@ export const externalizeDeps = (options: Partial<UserOptions> = {}): Plugin => {
     config: (_config, _env) => {
       if (existsSync(optionsResolved.useFile)) {
         const externalDeps = new Set<RegExp>()
-        const { dependencies = {}, peerDependencies = {} } = JSON.parse(readFileSync(optionsResolved.useFile).toString())
+        const { dependencies = {}, optionalDependencies = {}, peerDependencies = {} } = parseFile(optionsResolved.useFile)
 
         if (optionsResolved.deps) {
           Object.keys(dependencies).forEach((dep) => {
@@ -34,6 +38,14 @@ export const externalizeDeps = (options: Partial<UserOptions> = {}): Plugin => {
           })
         }
 
+        if (optionsResolved.optionalDeps) {
+          Object.keys(optionalDependencies).forEach((dep) => {
+            const depMatcher = new RegExp(`^${dep}(?:/.+)?$`)
+
+            externalDeps.add(depMatcher)
+          })
+        }
+
         if (optionsResolved.peerDeps) {
           Object.keys(peerDependencies).forEach((dep) => {
             const depMatcher = new RegExp(`^${dep}(?:/.+)?$`)