Add support for legacy decorators through tsconfig/jsconfig

.eslintignore

@@ -24,6 +24,7 @@ packages/next-codemod/**/*.d.ts
 packages/next-env/**/*.d.ts
 packages/create-next-app/templates/**
 test/integration/eslint/**
+test/development/basic/legacy-decorators/**/*
 test-timings.json
 packages/next/build/swc/tests/**
 bench/nested-deps/pages/**

packages/next/build/jest/jest.ts

@@ -2,7 +2,7 @@ import { loadEnvConfig } from '@next/env'
 import { resolve, join } from 'path'
 import loadConfig from '../../server/config'
 import { PHASE_TEST } from '../../shared/lib/constants'
-// import loadJsConfig from '../load-jsconfig'
+import loadJsConfig from '../load-jsconfig'
 import * as Log from '../output/log'
 
 async function getConfig(dir: string) {
@@ -51,7 +51,7 @@ export default function nextJest(options: { dir?: string } = {}) {
     // Will be called and awaited by Jest
     return async () => {
       let nextConfig
-      let paths
+      let jsConfig
       let resolvedBaseUrl
       let isEsmProject = false
       if (options.dir) {
@@ -62,9 +62,9 @@ export default function nextJest(options: { dir?: string } = {}) {
         nextConfig = await getConfig(resolvedDir)
         loadEnvConfig(resolvedDir, false, Log)
         // TODO: revisit when bug in SWC is fixed that strips `.css`
-        // const result = await loadJsConfig(resolvedDir, nextConfig)
-        // paths = result?.jsConfig?.compilerOptions?.paths
-        // resolvedBaseUrl = result.resolvedBaseUrl
+        const result = await loadJsConfig(resolvedDir, nextConfig)
+        jsConfig = result.jsConfig
+        resolvedBaseUrl = result.resolvedBaseUrl
       }
       // Ensure provided async config is supported
       const resolvedJestConfig =
@@ -107,10 +107,9 @@ export default function nextJest(options: { dir?: string } = {}) {
           '^.+\\.(js|jsx|ts|tsx)$': [
             require.resolve('../swc/jest-transformer'),
             {
-              styledComponents:
-                nextConfig && nextConfig.experimental.styledComponents,
-              paths,
-              resolvedBaseUrl: resolvedBaseUrl,
+              nextConfig,
+              jsConfig,
+              resolvedBaseUrl,
               isEsmProject,
             },
           ],

packages/next/build/swc/jest-transformer.js

@@ -48,9 +48,9 @@ module.exports = {
         isServer:
           jestConfig.testEnvironment && jestConfig.testEnvironment === 'node',
         filename,
-        styledComponents: inputOptions.styledComponents,
-        paths: inputOptions.paths,
-        baseUrl: inputOptions.resolvedBaseUrl,
+        nextConfig: inputOptions.nextConfig,
+        jsConfig: inputOptions.jsConfig,
+        resolvedBaseUrl: inputOptions.resolvedBaseUrl,
         esm:
           isSupportEsm &&
           isEsm(Boolean(inputOptions.isEsmProject), filename, jestConfig),

packages/next/build/swc/options.js

@@ -6,32 +6,36 @@ function getBaseSWCOptions({
   development,
   hasReactRefresh,
   globalWindow,
-  styledComponents,
-  paths,
-  baseUrl,
-  importSource,
+  nextConfig,
+  resolvedBaseUrl,
+  jsConfig,
 }) {
   const isTSFile = filename.endsWith('.ts')
   const isTypeScript = isTSFile || filename.endsWith('.tsx')
-
+  const paths = jsConfig?.compilerOptions?.paths
+  const enableDecorators = Boolean(
+    jsConfig?.compilerOptions?.experimentalDecorators
+  )
   return {
     jsc: {
-      ...(baseUrl && paths
+      ...(resolvedBaseUrl && paths
         ? {
-            baseUrl,
+            baseUrl: resolvedBaseUrl,
             paths,
           }
         : {}),
       parser: {
         syntax: isTypeScript ? 'typescript' : 'ecmascript',
         dynamicImport: true,
+        decorators: enableDecorators,
         // Exclude regular TypeScript files from React transformation to prevent e.g. generic parameters and angle-bracket type assertion from being interpreted as JSX tags.
         [isTypeScript ? 'tsx' : 'jsx']: isTSFile ? false : true,
       },
 
       transform: {
+        legacyDecorator: enableDecorators,
         react: {
-          importSource: importSource || 'react',
+          importSource: jsConfig?.compilerOptions?.jsxImportSource || 'react',
           runtime: 'automatic',
           pragma: 'React.createElement',
           pragmaFrag: 'React.Fragment',
@@ -57,7 +61,7 @@ function getBaseSWCOptions({
         },
       },
     },
-    styledComponents: styledComponents
+    styledComponents: nextConfig?.experimental?.styledComponents
       ? {
           displayName: Boolean(development),
         }
@@ -69,18 +73,19 @@ export function getJestSWCOptions({
   isServer,
   filename,
   esm,
-  styledComponents,
-  paths,
-  baseUrl,
+  nextConfig,
+  jsConfig,
+  // This is not passed yet as "paths" resolving needs a test first
+  // resolvedBaseUrl,
 }) {
   let baseOptions = getBaseSWCOptions({
     filename,
     development: false,
     hasReactRefresh: false,
     globalWindow: !isServer,
-    styledComponents,
-    paths,
-    baseUrl,
+    nextConfig,
+    jsConfig,
+    // resolvedBaseUrl,
   })
 
   const isNextDist = nextDistPath.test(filename)
@@ -108,16 +113,19 @@ export function getLoaderSWCOptions({
   pagesDir,
   isPageFile,
   hasReactRefresh,
-  styledComponents,
-  importSource,
+  nextConfig,
+  jsConfig,
+  // This is not passed yet as "paths" resolving is handled by webpack currently.
+  // resolvedBaseUrl,
 }) {
   let baseOptions = getBaseSWCOptions({
     filename,
     development,
     globalWindow: !isServer,
     hasReactRefresh,
-    styledComponents,
-    importSource,
+    nextConfig,
+    jsConfig,
+    // resolvedBaseUrl,
   })
 
   const isNextDist = nextDistPath.test(filename)

packages/next/build/webpack-config.ts

@@ -441,8 +441,8 @@ export default async function getBaseWebpackConfig(
             isServer: isMiddleware || isServer,
             pagesDir,
             hasReactRefresh: !isMiddleware && hasReactRefresh,
-            styledComponents: config.experimental.styledComponents,
-            importSource: jsConfig?.compilerOptions?.jsxImportSource,
+            nextConfig: config,
+            jsConfig,
           },
         }
       : {

packages/next/build/webpack/loaders/next-swc-loader.js

@@ -35,13 +35,8 @@ async function loaderTransform(parentTrace, source, inputSourceMap) {
 
   let loaderOptions = this.getOptions() || {}
 
-  const {
-    isServer,
-    pagesDir,
-    hasReactRefresh,
-    styledComponents,
-    importSource,
-  } = loaderOptions
+  const { isServer, pagesDir, hasReactRefresh, nextConfig, jsConfig } =
+    loaderOptions
   const isPageFile = filename.startsWith(pagesDir)
 
   const swcOptions = getLoaderSWCOptions({
@@ -51,8 +46,8 @@ async function loaderTransform(parentTrace, source, inputSourceMap) {
     isPageFile,
     development: this.mode === 'development',
     hasReactRefresh,
-    styledComponents,
-    importSource,
+    nextConfig,
+    jsConfig,
   })
 
   const programmaticOptions = {

test/development/basic/legacy-decorators.test.ts

@@ -0,0 +1,43 @@
+import { join } from 'path'
+import webdriver from 'next-webdriver'
+import { createNext, FileRef } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { check } from 'next-test-utils'
+
+describe('Legacy decorators SWC option', () => {
+  let next: NextInstance
+
+  beforeAll(async () => {
+    next = await createNext({
+      files: {
+        'jsconfig.json': new FileRef(
+          join(__dirname, 'legacy-decorators/jsconfig.json')
+        ),
+        pages: new FileRef(join(__dirname, 'legacy-decorators/pages')),
+      },
+      dependencies: {
+        mobx: '6.3.7',
+        'mobx-react': '7.2.1',
+      },
+    })
+  })
+  afterAll(() => next.destroy())
+
+  it('should compile with legacy decorators enabled', async () => {
+    let browser
+    try {
+      browser = await webdriver(next.appPort, '/')
+      const text = await browser.elementByCss('#count').text()
+      expect(text).toBe('Current number: 0')
+      await browser.elementByCss('#increase').click()
+      await check(
+        () => browser.elementByCss('#count').text(),
+        /Current number: 1/
+      )
+    } finally {
+      if (browser) {
+        await browser.close()
+      }
+    }
+  })
+})

test/development/basic/legacy-decorators/jsconfig.json

@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "experimentalDecorators": true
+  }
+}

test/development/basic/legacy-decorators/pages/index.js

@@ -0,0 +1,35 @@
+import React from 'react'
+import { makeAutoObservable } from 'mobx'
+import { observer } from 'mobx-react'
+
+class Counter {
+  count = 0
+
+  constructor() {
+    makeAutoObservable(this)
+  }
+
+  increase() {
+    this.count += 1
+  }
+}
+
+const myCounter = new Counter()
+
+@observer
+class CounterView extends React.Component {
+  render() {
+    return (
+      <>
+        <span id="count">Current number: {this.props.counter.count}</span>
+        <button id="increase" onClick={() => this.props.counter.increase()}>
+          Increase
+        </button>
+      </>
+    )
+  }
+}
+
+export default function Home() {
+  return <CounterView counter={myCounter} />
+}