feat: add ESM support for generated project (#583)

This adds ESM support to the generated project. To do this:

- Use `.cjs` and `.mjs` file extensions for the generated files
- Add file extensions to imports in the compiled code
- Add the `exports` field in `package.json`
- Update the `moduleResolution` config to `Bundler` in `tsconfig.json`

In addition:

- Enable the new JSX runtime option for React
- Recommend removing the `react-native` field from `package.json`

This is a breaking change for library authors. After upgrading, it's
necessary to update the configuration by running the following command:

```sh
yarn bob init
```

Alternatively, they can follow the [manual configuration
guide](https://callstack.github.io/react-native-builder-bob/build#manual-configuration).

In addition, typescript consumers would need to change the following
fields in `tsconfig.json`:

```json
"jsx": "react-jsx",
"moduleResolution": "Bundler",
```

If using ESLint, it may also be necessary to disable the
"react/react-in-jsx-scope" rule:

```json
"react/react-in-jsx-scope": "off"
```

.github/workflows/build-templates.yml

@@ -200,8 +200,6 @@ jobs:
         working-directory: ${{ env.work_dir }}
         run: |
           yarn typecheck
-        # FIXME: Remove this once we fix the typecheck errors
-        continue-on-error: true
 
       - name: Test library
         working-directory: ${{ env.work_dir }}

docs/pages/build.md

@@ -73,11 +73,17 @@ yarn add --dev react-native-builder-bob
 1. Configure the appropriate entry points:
 
    ```json
-   "main": "lib/commonjs/index.js",
-   "module": "lib/module/index.js",
-   "react-native": "src/index.ts",
-   "types": "lib/typescript/src/index.d.ts",
-   "source": "src/index.ts",
+   "source": "./src/index.tsx",
+   "main": "./lib/commonjs/index.cjs",
+   "module": "./lib/module/index.mjs",
+   "types": "./lib/typescript/src/index.d.ts",
+   "exports": {
+     ".": {
+       "types": "./typescript/src/index.d.ts",
+       "require": "./commonjs/index.cjs",
+       "import": "./module/index.mjs"
+     }
+   },
    "files": [
      "lib",
      "src"
@@ -88,7 +94,6 @@ yarn add --dev react-native-builder-bob
 
    - `main`: The entry point for the commonjs build. This is used by Node - such as tests, SSR etc.
    - `module`: The entry point for the ES module build. This is used by bundlers such as webpack.
-   - `react-native`: The entry point for the React Native apps. This is used by Metro. It's common to point to the source code here as it can make debugging easier.
    - `types`: The entry point for the TypeScript definitions. This is used by TypeScript to type check the code using your library.
    - `source`: The path to the source code. It is used by `react-native-builder-bob` to detect the correct output files and provide better error messages.
    - `files`: The files to include in the package when publishing with `npm`.
@@ -150,7 +155,7 @@ Various targets to build for. The available targets are:
 
 Enable compiling source files with Babel and use commonjs module system.
 
-This is useful for running the code in Node (SSR, tests etc.). The output file should be referenced in the `main` field of `package.json`.
+This is useful for running the code in Node (SSR, tests etc.). The output file should be referenced in the `main` field and `exports['.'].require` field of `package.json`.
 
 By default, the code is compiled to support last 2 versions of modern browsers. It also strips TypeScript and Flow annotations, and compiles JSX. You can customize the environments to compile for by using a [browserslist config](https://github.com/browserslist/browserslist#config-file).
 
@@ -174,7 +179,7 @@ Example:
 
 Enable compiling source files with Babel and use ES module system. This is essentially same as the `commonjs` target and accepts the same options, but leaves the `import`/`export` statements in your code.
 
-This is useful for bundlers which understand ES modules and can tree-shake. The output file should be referenced in the `module` field of `package.json`.
+This is useful for bundlers which understand ES modules and can tree-shake. The output file should be referenced in the `module` field and `exports['.'].import` field of `package.json`.
 
 Example:
 
@@ -198,6 +203,8 @@ Example:
 ["typescript", { "project": "tsconfig.build.json" }]
 ```
 
+The output file should be referenced in the `types` field or `exports['.'].types` field of `package.json`.
+
 ## Commands
 
 The `bob` CLI exposes the following commands:

packages/create-react-native-library/src/index.ts

@@ -14,7 +14,7 @@ import generateExampleApp, {
 import { spawn } from './utils/spawn';
 import { version } from '../package.json';
 
-const FALLBACK_BOB_VERSION = '0.20.0';
+const FALLBACK_BOB_VERSION = '0.25.0';
 
 const BINARIES = [
   /(gradlew|\.(jar|keystore|png|jpg|gif))$/,

packages/create-react-native-library/templates/common-example/example/src/App.tsx

@@ -1,9 +1,10 @@
-import * as React from 'react';
-
 <% if (project.view) { -%>
 import { StyleSheet, View } from 'react-native';
 import { <%- project.name -%>View } from '<%- project.slug -%>';
 <% } else { -%>
+<% if (project.arch !== 'new') { -%>
+import { useState, useEffect } from 'react';
+<% } -%>
 import { StyleSheet, View, Text } from 'react-native';
 import { multiply } from '<%- project.slug -%>';
 <% } -%>
@@ -28,9 +29,9 @@ export default function App() {
 }
 <% } else { -%>
 export default function App() {
-  const [result, setResult] = React.useState<number | undefined>();
+  const [result, setResult] = useState<number | undefined>();
 
-  React.useEffect(() => {
+  useEffect(() => {
     multiply(3, 7).then(setResult);
   }, []);
 

packages/create-react-native-library/templates/common/$package.json

@@ -2,11 +2,17 @@
   "name": "<%- project.slug -%>",
   "version": "0.1.0",
   "description": "<%- project.description %>",
-  "main": "lib/commonjs/index",
-  "module": "lib/module/index",
-  "types": "lib/typescript/src/index.d.ts",
-  "react-native": "src/index",
-  "source": "src/index",
+  "source": "./src/index.tsx",
+  "main": "./lib/commonjs/index.cjs",
+  "module": "./lib/module/index.mjs",
+  "types": "./lib/typescript/src/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./lib/typescript/src/index.d.ts",
+      "import": "./lib/module/index.mjs",
+      "require": "./lib/commonjs/index.cjs"
+    }
+  },
   "files": [
     "src",
     "lib",
@@ -130,6 +136,7 @@
       "prettier"
     ],
     "rules": {
+      "react/react-in-jsx-scope": "off",
       "prettier/prettier": [
         "error",
         {

packages/create-react-native-library/templates/common/tsconfig.json

@@ -8,10 +8,10 @@
     "allowUnusedLabels": false,
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
-    "jsx": "react",
-    "lib": ["esnext"],
-    "module": "esnext",
-    "moduleResolution": "node",
+    "jsx": "react-jsx",
+    "lib": ["ESNext"],
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
     "noFallthroughCasesInSwitch": true,
     "noImplicitReturns": true,
     "noImplicitUseStrict": false,
@@ -22,7 +22,7 @@
     "resolveJsonModule": true,
     "skipLibCheck": true,
     "strict": true,
-    "target": "esnext",
+    "target": "ESNext",
     "verbatimModuleSyntax": true
   }
 }

packages/react-native-builder-bob/babel-preset.js

@@ -3,6 +3,8 @@
 const browserslist = require('browserslist');
 
 module.exports = function (api, options, cwd) {
+  const cjs = options.modules === 'commonjs';
+
   return {
     presets: [
       [
@@ -24,12 +26,25 @@ module.exports = function (api, options, cwd) {
             node: '18',
           },
           useBuiltIns: false,
-          modules: options.modules || false,
+          modules: cjs ? 'commonjs' : false,
+        },
+      ],
+      [
+        require.resolve('@babel/preset-react'),
+        {
+          runtime: 'automatic',
         },
       ],
-      require.resolve('@babel/preset-react'),
       require.resolve('@babel/preset-typescript'),
       require.resolve('@babel/preset-flow'),
     ],
+    plugins: [
+      [
+        require.resolve('./lib/babel'),
+        {
+          extension: cjs ? 'cjs' : 'mjs',
+        },
+      ],
+    ],
   };
 };

packages/react-native-builder-bob/src/index.ts

@@ -28,7 +28,7 @@ yargs
       const { shouldContinue } = await prompts({
         type: 'confirm',
         name: 'shouldContinue',
-        message: `The working directory is not clean. You should commit or stash your changes before configuring bob. Continue anyway?`,
+        message: `The working directory is not clean.\n  You should commit or stash your changes before configuring bob.\n  Continue anyway?`,
         initial: false,
       });
 
@@ -41,7 +41,7 @@ yargs
 
     if (!(await fs.pathExists(pak))) {
       logger.exit(
-        `Couldn't find a 'package.json' file in '${root}'. Are you in a project folder?`
+        `Couldn't find a 'package.json' file in '${root}'.\n  Are you in a project folder?`
       );
     }
 
@@ -52,7 +52,7 @@ yargs
       const { shouldContinue } = await prompts({
         type: 'confirm',
         name: 'shouldContinue',
-        message: `The project seems to be already configured with bob. Do you want to overwrite the existing configuration?`,
+        message: `The project seems to be already configured with bob.\n  Do you want to overwrite the existing configuration?`,
         initial: false,
       });
 
@@ -81,7 +81,7 @@ yargs
 
     if (!entryFile) {
       logger.exit(
-        `Couldn't find a 'index.js'. 'index.ts' or 'index.tsx' file under '${source}'. Please re-run the CLI after creating it.`
+        `Couldn't find a 'index.js'. 'index.ts' or 'index.tsx' file under '${source}'.\n  Please re-run the CLI after creating it.`
       );
       return;
     }
@@ -147,26 +147,34 @@ yargs
         ? targets[0]
         : undefined;
 
-    const entries: { [key: string]: string } = {
-      'main': target
-        ? path.join(output, target, 'index.js')
-        : path.join(source, entryFile),
-      'react-native': path.join(source, entryFile),
-      'source': path.join(source, entryFile),
+    const entries: {
+      [key in 'source' | 'main' | 'module' | 'types']?: string;
+    } = {
+      source: `./${path.join(source, entryFile)}`,
+      main: `./${
+        target
+          ? path.join(output, target, 'index.cjs')
+          : path.join(source, entryFile)
+      }`,
     };
 
     if (targets.includes('module')) {
-      entries.module = path.join(output, 'module', 'index.js');
+      entries.module = `./${path.join(output, 'module', 'index.mjs')}`;
     }
 
     if (targets.includes('typescript')) {
-      entries.types = path.join(output, 'typescript', source, 'index.d.ts');
+      entries.types = `./${path.join(
+        output,
+        'typescript',
+        source,
+        'index.d.ts'
+      )}`;
 
       if (!(await fs.pathExists(path.join(root, 'tsconfig.json')))) {
         const { tsconfig } = await prompts({
           type: 'confirm',
           name: 'tsconfig',
-          message: `You have enabled 'typescript' compilation, but we couldn't find a 'tsconfig.json' in project root. Generate one?`,
+          message: `You have enabled 'typescript' compilation, but we couldn't find a 'tsconfig.json' in project root.\n  Generate one?`,
           initial: true,
         });
 
@@ -180,10 +188,10 @@ yargs
                 allowUnusedLabels: false,
                 esModuleInterop: true,
                 forceConsistentCasingInFileNames: true,
-                jsx: 'react',
-                lib: ['esnext'],
-                module: 'esnext',
-                moduleResolution: 'node',
+                jsx: 'react-jsx',
+                lib: ['ESNext'],
+                module: 'ESNext',
+                moduleResolution: 'Bundler',
                 noFallthroughCasesInSwitch: true,
                 noImplicitReturns: true,
                 noImplicitUseStrict: false,
@@ -194,7 +202,7 @@ yargs
                 resolveJsonModule: true,
                 skipLibCheck: true,
                 strict: true,
-                target: 'esnext',
+                target: 'ESNext',
                 verbatimModuleSyntax: true,
               },
             },
@@ -214,13 +222,13 @@ yargs
     ];
 
     for (const key in entries) {
-      const entry = entries[key];
+      const entry = entries[key as keyof typeof entries];
 
       if (pkg[key] && pkg[key] !== entry) {
         const { replace } = await prompts({
           type: 'confirm',
           name: 'replace',
-          message: `Your package.json has the '${key}' field set to '${pkg[key]}'. Do you want to replace it with '${entry}'?`,
+          message: `Your package.json has the '${key}' field set to '${pkg[key]}'.\n  Do you want to replace it with '${entry}'?`,
           initial: true,
         });
 
@@ -232,11 +240,60 @@ yargs
       }
     }
 
+    if (Object.values(entries).some((entry) => entry.endsWith('.mjs'))) {
+      let replace = false;
+
+      const exports = {
+        '.': {
+          ...(entries.types ? { types: entries.types } : null),
+          ...(entries.module ? { import: entries.module } : null),
+          ...(entries.main ? { require: entries.main } : null),
+        },
+      };
+
+      if (
+        pkg.exports &&
+        JSON.stringify(pkg.exports) !== JSON.stringify(exports)
+      ) {
+        replace = (
+          await prompts({
+            type: 'confirm',
+            name: 'replace',
+            message: `Your package.json has 'exports' field set.\n  Do you want to replace it?`,
+            initial: true,
+          })
+        ).replace;
+      } else {
+        replace = true;
+      }
+
+      if (replace) {
+        pkg.exports = exports;
+      }
+    }
+
+    if (
+      pkg['react-native'] &&
+      (pkg['react-native'].startsWith(source) ||
+        pkg['react-native'].startsWith(`./${source}`))
+    ) {
+      const { remove } = await prompts({
+        type: 'confirm',
+        name: 'remove',
+        message: `Your package.json has the 'react-native' field pointing to source code.\n  This can cause problems when customizing babel configuration.\n  Do you want to remove it?`,
+        initial: true,
+      });
+
+      if (remove) {
+        delete pkg['react-native'];
+      }
+    }
+
     if (pkg.scripts?.prepare && pkg.scripts.prepare !== prepare) {
       const { replace } = await prompts({
         type: 'confirm',
         name: 'replace',
-        message: `Your package.json has the 'scripts.prepare' field set to '${pkg.scripts.prepare}'. Do you want to replace it with '${prepare}'?`,
+        message: `Your package.json has the 'scripts.prepare' field set to '${pkg.scripts.prepare}'.\n  Do you want to replace it with '${prepare}'?`,
         initial: true,
       });
 
@@ -256,7 +313,7 @@ yargs
       const { update } = await prompts({
         type: 'confirm',
         name: 'update',
-        message: `Your package.json already has a 'files' field. Do you want to update it?`,
+        message: `Your package.json already has a 'files' field.\n  Do you want to update it?`,
         initial: true,
       });
 

packages/react-native-builder-bob/src/targets/commonjs.ts

@@ -36,6 +36,5 @@ export default async function build({
     exclude,
     modules: 'commonjs',
     report,
-    field: 'main',
   });
 }

packages/react-native-builder-bob/src/targets/module.ts

@@ -36,6 +36,5 @@ export default async function build({
     exclude,
     modules: false,
     report,
-    field: 'module',
   });
 }