feat: allow write to be true so the file loader can be used (#34)

* feat: allow `write` to be `true` so the file loader can be used

* docs: add image bundling to readme

* update esbuild to 0.11.16

* docs: add note about node-gyp to the readme, closes #35

* run format and fix typo

Closes #35
Closes #26

.gitignore

@@ -2,6 +2,7 @@ node_modules
 coverage
 dist
 .DS_Store
+output/
 
 # these cause more harm than good
 # when working with contributors

README.md

@@ -195,6 +195,9 @@ should be installed as one of your project's `dependencies`:
 npm install --save mdx-bundler
 ```
 
+One of mdx-bundler's dependancies requires a working [node-gyp][node-gyp] setup
+to be able to install correctly.
+
 ## Usage
 
 ```typescript
@@ -481,6 +484,68 @@ export const exampleImage = 'https://example.com/image.jpg'
 <img src={exampleImage} alt="Image alt text" />
 ```
 
+### Image Bundling
+
+With the [cwd](#cwd) and the remark plugin
+[remark-mdx-images](https://www.npmjs.com/package/remark-mdx-images) you can
+bundle images in your mdx!
+
+There are two loaders in esbuild that can be used here. The easiest is `dataurl`
+which outputs the images as inline data urls in the returned code.
+
+```js
+import {remarkMdxImages} from 'remark-mdx-images'
+
+const {code} = await bundleMDX(mdxSource, {
+  cwd: '/users/you/site/_content/pages',
+  xdmOptions: (vFile, options) => {
+    options.remarkPlugins = [remarkMdxImages]
+
+    return options
+  },
+  esbuildOptions: options => {
+    options.loader = {
+      ...options.loader,
+      '.png': 'dataurl',
+    }
+
+    return options
+  },
+})
+```
+
+The `file` loader requires a little more configuration to get working. With the
+`file` loader your images are copied to the output directory so esbuild needs to
+be set to write files and needs to know where to put them plus the url of the
+folder to be used in image sources.
+
+```js
+const {code} = await bundleMDX(mdxSource, {
+  cwd: '/users/you/site/_content/pages',
+  xdmOptions: (vFile, options) => {
+    options.remarkPlugins = [remarkMdxImages]
+
+    return options
+  },
+  esbuildOptions: options => {
+    // Set the `outdir` to your public directory.
+    options.outdir = '/users/you/site/public/img'
+    options.loader = {
+      ...options.loader,
+      // Tell esbuild to use the `file` loader for pngs
+      '.png': 'file',
+    }
+    // Set the public path to /img/ so image sources start /img/
+    options.publicPath = '/img/'
+
+    // Set write to true so that esbuild will output the files.
+    options.write = true
+
+    return options
+  },
+})
+```
+
 ### Known Issues
 
 #### Cloudflare Workers
@@ -624,4 +689,5 @@ MIT
 [bugs]: https://github.com/kentcdodds/mdx-bundler/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Acreated-desc+label%3Abug
 [requests]: https://github.com/kentcdodds/mdx-bundler/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3Aenhancement
 [good-first-issue]: https://github.com/kentcdodds/mdx-bundler/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3Aenhancement+label%3A%22good+first+issue%22
+[node-gyp]: https://github.com/nodejs/node-gyp#installation
 <!-- prettier-ignore-end -->

package.json

@@ -43,7 +43,7 @@
     "@babel/runtime": "^7.13.17",
     "@esbuild-plugins/node-resolve": "^0.1.4",
     "@fal-works/esbuild-plugin-global-externals": "^2.1.1",
-    "esbuild": "^0.11.15",
+    "esbuild": "^0.11.16",
     "gray-matter": "^4.0.3",
     "jsdom": "^16.5.3",
     "remark-frontmatter": "^3.0.0",

src/__tests__/index.js

@@ -5,6 +5,7 @@ import React from 'react'
 import rtl from '@testing-library/react'
 import leftPad from 'left-pad'
 import {remarkMdxImages} from 'remark-mdx-images'
+import path from 'path'
 import {bundleMDX} from '../index.js'
 import {getMDXComponent} from '../client.js'
 
@@ -293,4 +294,62 @@ import {Sample} from './other/sample-component'
   )
 })
 
+test('should output assets', async () => {
+  const mdxSource = `
+# Sample Post
+
+![Sample Image](./other/150.png)
+  `.trim()
+
+  const {code} = await bundleMDX(mdxSource, {
+    cwd: process.cwd(),
+    xdmOptions: (vFile, options) => {
+      options.remarkPlugins = [remarkMdxImages]
+
+      return options
+    },
+    esbuildOptions: options => {
+      options.outdir = path.join(process.cwd(), 'output')
+      options.loader = {
+        ...options.loader,
+        '.png': 'file',
+      }
+      options.publicPath = '/img/'
+      options.write = true
+
+      return options
+    },
+  })
+
+  const Component = getMDXComponent(code)
+
+  const {container} = render(React.createElement(Component))
+
+  assert.match(container.innerHTML, 'src="/img/150')
+
+  const error = /** @type Error */ (await bundleMDX(mdxSource, {
+    cwd: process.cwd(),
+    xdmOptions: (vFile, options) => {
+      options.remarkPlugins = [remarkMdxImages]
+
+      return options
+    },
+    esbuildOptions: options => {
+      options.loader = {
+        ...options.loader,
+        // esbuild will throw its own error if we try to use `file` loader without `outdir`
+        '.png': 'dataurl',
+      }
+      options.write = true
+
+      return options
+    },
+  }).catch(e => e))
+
+  assert.equal(
+    error.message,
+    "You must either specify `write: false` or `write: true` and `outdir: '/path'` in your esbuild options",
+  )
+})
+
 test.run()

src/index.js

@@ -1,3 +1,4 @@
+import fs from 'fs'
 import path from 'path'
 import {StringDecoder} from 'string_decoder'
 import remarkFrontmatter from 'remark-frontmatter'
@@ -8,6 +9,8 @@ import {NodeResolvePlugin} from '@esbuild-plugins/node-resolve'
 import {globalExternals} from '@fal-works/esbuild-plugin-global-externals'
 import dirnameMessedUp from './dirname-messed-up.cjs'
 
+const {readFile, unlink} = fs.promises
+
 /**
  *
  * @param {string} mdxSource - A string of mdx source code
@@ -149,14 +152,33 @@ async function bundleMDX(
 
   const bundled = await esbuild.build(buildOptions)
 
-  const decoder = new StringDecoder('utf8')
+  if (bundled.outputFiles) {
+    const decoder = new StringDecoder('utf8')
 
-  const code = decoder.write(Buffer.from(bundled.outputFiles[0].contents))
+    const code = decoder.write(Buffer.from(bundled.outputFiles[0].contents))
 
-  return {
-    code: `${code};return Component.default;`,
-    frontmatter,
+    return {
+      code: `${code};return Component.default;`,
+      frontmatter,
+    }
   }
+
+  if (buildOptions.outdir && buildOptions.write) {
+    const code = await readFile(
+      path.join(buildOptions.outdir, '_mdx_bundler_entry_point.js'),
+    )
+
+    await unlink(path.join(buildOptions.outdir, '_mdx_bundler_entry_point.js'))
+
+    return {
+      code: `${code};return Component.default;`,
+      frontmatter,
+    }
+  }
+
+  throw new Error(
+    "You must either specify `write: false` or `write: true` and `outdir: '/path'` in your esbuild options",
+  )
 }
 
 export {bundleMDX}

src/types.d.ts

@@ -8,7 +8,7 @@ import type {Plugin, BuildOptions, Loader} from 'esbuild'
 import type {ModuleInfo} from '@fal-works/esbuild-plugin-global-externals'
 import type {VFileCompatible, CompileOptions} from 'xdm/lib/compile'
 
-type ESBuildOptions = BuildOptions & {write: false}
+type ESBuildOptions = BuildOptions
 
 type BundleMDXOptions = {
   /**