Add experimental cra-to-next transform in codemod cli

packages/next-codemod/bin/cli.ts

@@ -8,18 +8,18 @@
 // Based on https://github.com/reactjs/react-codemod/blob/dd8671c9a470a2c342b221ec903c574cf31e9f57/bin/cli.js
 // @next/codemod optional-name-of-transform optional/path/to/src [...options]
 
-const globby = require('globby')
-const inquirer = require('inquirer')
-const meow = require('meow')
-const path = require('path')
-const execa = require('execa')
-const chalk = require('chalk')
-const isGitClean = require('is-git-clean')
-
-const transformerDirectory = path.join(__dirname, '../', 'transforms')
-const jscodeshiftExecutable = require.resolve('.bin/jscodeshift')
-
-function checkGitStatus(force) {
+import globby from 'globby'
+import inquirer from 'inquirer'
+import meow from 'meow'
+import path from 'path'
+import execa from 'execa'
+import chalk from 'chalk'
+import isGitClean from 'is-git-clean'
+
+export const jscodeshiftExecutable = require.resolve('.bin/jscodeshift')
+export const transformerDirectory = path.join(__dirname, '../', 'transforms')
+
+export function checkGitStatus(force) {
   let clean = false
   let errorMessage = 'Unable to determine if git directory is clean'
   try {
@@ -49,19 +49,27 @@ function checkGitStatus(force) {
   }
 }
 
-function runTransform({ files, flags, transformer }) {
+export function runTransform({ files, flags, transformer }) {
   const transformerPath = path.join(transformerDirectory, `${transformer}.js`)
 
+  if (transformer === 'cra-to-next') {
+    // cra-to-next transform doesn't use jscodeshift directly
+    return require(transformerPath).default(files, flags)
+  }
+
   let args = []
 
-  const { dry, print } = flags
+  const { dry, print, runInBand } = flags
 
   if (dry) {
     args.push('--dry')
   }
   if (print) {
     args.push('--print')
   }
+  if (runInBand) {
+    args.push('--run-in-band')
+  }
 
   args.push('--verbose=2')
 
@@ -83,11 +91,11 @@ function runTransform({ files, flags, transformer }) {
 
   const result = execa.sync(jscodeshiftExecutable, args, {
     stdio: 'inherit',
-    stripEof: false,
+    stripFinalNewline: false,
   })
 
-  if (result.error) {
-    throw result.error
+  if (result.failed) {
+    throw new Error(`jscodeshift exited with code ${result.exitCode}`)
   }
 }
 
@@ -112,6 +120,11 @@ const TRANSFORMER_INQUIRER_CHOICES = [
       'url-to-withrouter: Transforms the deprecated automatically injected url property on top level pages to using withRouter',
     value: 'url-to-withrouter',
   },
+  {
+    name:
+      'cra-to-next: automatically migrates a create-react-app project to leverage Next.js instead',
+    value: 'cra-to-next',
+  },
 ]
 
 function expandFilePathsIfNeeded(filesBeforeExpansion) {
@@ -123,11 +136,10 @@ function expandFilePathsIfNeeded(filesBeforeExpansion) {
     : filesBeforeExpansion
 }
 
-function run() {
-  const cli = meow(
-    {
-      description: 'Codemods for updating Next.js apps.',
-      help: `
+export function run() {
+  const cli = meow({
+    description: 'Codemods for updating Next.js apps.',
+    help: `
     Usage
       $ npx @next/codemod <transform> <path> <...options>
         transform    One of the choices from https://github.com/vercel/next.js/tree/canary/packages/next-codemod
@@ -138,15 +150,14 @@ function run() {
       --print            Print transformed files to your terminal
       --jscodeshift  (Advanced) Pass options directly to jscodeshift
     `,
-    },
-    {
+    flags: {
       boolean: ['force', 'dry', 'print', 'help'],
       string: ['_'],
       alias: {
         h: 'help',
       },
-    }
-  )
+    },
+  } as meow.Options<meow.AnyFlags>)
 
   if (!cli.flags.dry) {
     checkGitStatus(cli.flags.force)
@@ -203,11 +214,3 @@ function run() {
       })
     })
 }
-
-module.exports = {
-  run: run,
-  runTransform: runTransform,
-  checkGitStatus: checkGitStatus,
-  jscodeshiftExecutable: jscodeshiftExecutable,
-  transformerDirectory: transformerDirectory,
-}

packages/next-codemod/lib/cra-to-next/gitignore

@@ -0,0 +1,34 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# local env files
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# vercel
+.vercel

packages/next-codemod/lib/cra-to-next/global-css-transform.ts

@@ -0,0 +1,65 @@
+import nodePath from 'path'
+import { API, FileInfo, Options } from 'jscodeshift'
+
+export const globalCssContext = {
+  cssImports: new Set<string>(),
+  reactSvgImports: new Set<string>(),
+}
+const globalStylesRegex = /(?<!\.module)\.(css|scss|sass)$/i
+
+export default function transformer(
+  file: FileInfo,
+  api: API,
+  options: Options
+) {
+  const j = api.jscodeshift
+  const root = j(file.source)
+  let hasModifications = false
+
+  root
+    .find(j.ImportDeclaration)
+    .filter((path) => {
+      const {
+        node: {
+          source: { value },
+        },
+      } = path
+
+      if (typeof value === 'string') {
+        if (globalStylesRegex.test(value)) {
+          let resolvedPath = value
+
+          if (value.startsWith('.')) {
+            resolvedPath = nodePath.resolve(nodePath.dirname(file.path), value)
+          }
+          globalCssContext.cssImports.add(resolvedPath)
+
+          const { start, end } = path.node as any
+
+          if (!path.parentPath.node.comments) {
+            path.parentPath.node.comments = []
+          }
+
+          path.parentPath.node.comments = [
+            j.commentLine(' ' + file.source.substring(start, end)),
+          ]
+          hasModifications = true
+          return true
+        } else if (value.endsWith('.svg')) {
+          const isComponentImport = path.node.specifiers.some((specifier) => {
+            return (specifier as any).imported?.name === 'ReactComponent'
+          })
+
+          if (isComponentImport) {
+            globalCssContext.reactSvgImports.add(file.path)
+          }
+        }
+      }
+      return false
+    })
+    .remove()
+
+  return hasModifications && globalCssContext.reactSvgImports.size === 0
+    ? root.toSource(options)
+    : null
+}

packages/next-codemod/lib/cra-to-next/index-to-component.ts

@@ -0,0 +1,101 @@
+import { API, FileInfo, JSXElement, Options } from 'jscodeshift'
+
+export const indexContext = {
+  multipleRenderRoots: false,
+  nestedRender: false,
+}
+
+export default function transformer(
+  file: FileInfo,
+  api: API,
+  options: Options
+) {
+  const j = api.jscodeshift
+  const root = j(file.source)
+  let hasModifications = false
+  let foundReactRender = 0
+  let hasRenderImport = false
+  let defaultReactDomImport: string | undefined
+
+  root.find(j.ImportDeclaration).forEach((path) => {
+    if (path.node.source.value === 'react-dom') {
+      return path.node.specifiers.forEach((specifier) => {
+        if (specifier.local.name === 'render') {
+          hasRenderImport = true
+        }
+        if (specifier.type === 'ImportDefaultSpecifier') {
+          defaultReactDomImport = specifier.local.name
+        }
+      })
+    }
+    return false
+  })
+
+  root
+    .find(j.CallExpression)
+    .filter((path) => {
+      const { node } = path
+      let found = false
+
+      if (
+        defaultReactDomImport &&
+        node.callee.type === 'MemberExpression' &&
+        (node.callee.object as any).name === defaultReactDomImport &&
+        (node.callee.property as any).name === 'render'
+      ) {
+        found = true
+      }
+
+      if (hasRenderImport && (node.callee as any).name === 'render') {
+        found = true
+      }
+
+      if (found) {
+        foundReactRender++
+        hasModifications = true
+
+        if (!Array.isArray(path.parentPath?.parentPath?.value)) {
+          indexContext.nestedRender = true
+          return false
+        }
+
+        const newNode = j.exportDefaultDeclaration(
+          j.functionDeclaration(
+            j.identifier('NextIndexWrapper'),
+            [],
+            j.blockStatement([
+              j.returnStatement(
+                // TODO: remove React.StrictMode wrapper and use
+                // next.config.js option instead?
+                path.node.arguments.find(
+                  (a) => a.type === 'JSXElement'
+                ) as JSXElement
+              ),
+            ])
+          )
+        )
+
+        path.parentPath.insertBefore(newNode)
+        return true
+      }
+      return false
+    })
+    .remove()
+
+  indexContext.multipleRenderRoots = foundReactRender > 1
+  hasModifications =
+    hasModifications &&
+    !indexContext.nestedRender &&
+    !indexContext.multipleRenderRoots
+
+  // TODO: move function passed to reportWebVitals if present to
+  // _app reportWebVitals and massage values to expected shape
+
+  // root.find(j.CallExpression, {
+  //   callee: {
+  //     name: 'reportWebVitals'
+  //   }
+  // }).remove()
+
+  return hasModifications ? root.toSource(options) : null
+}