feat: add support for multipart/form-data (nodejs#1606)

* add support for multipart/form-data

* Handle busboy errors

* linting

* Catch emitted error

* reject promise instead of throwing error

* Add test for base64 encoded multipart/form-data

Thanks for the help @mrbbot !

* Move busboy from devDependencies to dependencies

* Add test for busboy emitting error

* Rewrite tests

* Update tests to avoid promises and callbacks

Author: cameron-robey

lib/fetch/body.js

@@ -1,5 +1,6 @@
 'use strict'
 
+const Busboy = require('busboy')
 const util = require('../core/util')
 const { ReadableStreamFrom, toUSVString, isBlobLike } = require('./util')
 const { FormData } = require('./formdata')
@@ -9,9 +10,9 @@ const { DOMException } = require('./constants')
 const { Blob } = require('buffer')
 const { kBodyUsed } = require('../core/symbols')
 const assert = require('assert')
-const { NotSupportedError } = require('../core/errors')
 const { isErrored } = require('../core/util')
 const { isUint8Array, isArrayBuffer } = require('util/types')
+const { File } = require('./file')
 
 let ReadableStream
 
@@ -414,7 +415,47 @@ function bodyMixinMethods (instance) {
 
       // If mimeType’s essence is "multipart/form-data", then:
       if (/multipart\/form-data/.test(contentType)) {
-        throw new NotSupportedError('multipart/form-data not supported')
+        const headers = {}
+        for (const [key, value] of this.headers) headers[key.toLowerCase()] = value
+
+        const responseFormData = new FormData()
+
+        let busboy
+
+        try {
+          busboy = Busboy({ headers })
+        } catch (err) {
+          // Error due to headers:
+          throw Object.assign(new TypeError(), { cause: err })
+        }
+
+        busboy.on('field', (name, value) => {
+          responseFormData.append(name, value)
+        })
+        busboy.on('file', (name, value, info) => {
+          const { filename, encoding, mimeType } = info
+          const base64 = encoding.toLowerCase() === 'base64'
+          const chunks = []
+          value.on('data', (chunk) => {
+            if (base64) chunk = Buffer.from(chunk.toString(), 'base64')
+            chunks.push(chunk)
+          })
+          value.on('end', () => {
+            const file = new File(chunks, filename, { type: mimeType })
+            responseFormData.append(name, file)
+          })
+        })
+
+        const busboyResolve = new Promise((resolve, reject) => {
+          busboy.on('finish', resolve)
+          busboy.on('error', (err) => reject(err))
+        })
+
+        if (this.body !== null) for await (const chunk of consumeBody(this[kState].body)) busboy.write(chunk)
+        busboy.end()
+        await busboyResolve
+
+        return responseFormData
       } else if (/application\/x-www-form-urlencoded/.test(contentType)) {
         // Otherwise, if mimeType’s essence is "application/x-www-form-urlencoded", then:
 

package.json

@@ -69,7 +69,6 @@
     "@types/node": "^17.0.45",
     "abort-controller": "^3.0.0",
     "atomic-sleep": "^1.0.0",
-    "busboy": "^1.6.0",
     "chai": "^4.3.4",
     "chai-as-promised": "^7.1.1",
     "chai-iterator": "^3.0.2",
@@ -125,5 +124,8 @@
     "testMatch": [
       "<rootDir>/test/jest/**"
     ]
+  },
+  "dependencies": {
+    "busboy": "^1.6.0"
   }
 }

test/fetch/client-fetch.js

@@ -11,6 +11,7 @@ const { Client, setGlobalDispatcher, Agent } = require('../..')
 const nodeFetch = require('../../index-fetch')
 const { once } = require('events')
 const { gzipSync } = require('zlib')
+const { promisify } = require('util')
 
 setGlobalDispatcher(new Agent({
   keepAliveTimeout: 1,
@@ -165,24 +166,80 @@ test('unsupported formData 1', (t) => {
   })
 })
 
-test('unsupported formData 2', (t) => {
+test('multipart formdata not base64', async (t) => {
+  t.plan(2)
+  // Construct example form data, with text and blob fields
+  const formData = new FormData()
+  formData.append('field1', 'value1')
+  const blob = new Blob(['example\ntext file'], { type: 'text/plain' })
+  formData.append('field2', blob, 'file.txt')
+
+  const tempRes = new Response(formData)
+  const boundary = tempRes.headers.get('content-type').split('boundary=')[1]
+  const formRaw = await tempRes.text()
+
+  const server = createServer((req, res) => {
+    res.setHeader('content-type', 'multipart/form-data; boundary=' + boundary)
+    res.write(formRaw)
+    res.end()
+  })
+  t.teardown(server.close.bind(server))
+
+  const listen = promisify(server.listen.bind(server))
+  await listen(0)
+
+  const res = await fetch(`http://localhost:${server.address().port}`)
+  const form = await res.formData()
+  t.equal(form.get('field1'), 'value1')
+
+  const text = await form.get('field2').text()
+  t.equal(text, 'example\ntext file')
+})
+
+test('multipart formdata base64', (t) => {
   t.plan(1)
 
+  // Example form data with base64 encoding
+  const formRaw = '------formdata-undici-0.5786922755719377\r\nContent-Disposition: form-data; name="key"; filename="test.txt"\r\nContent-Type: text/plain\r\nContent-Transfer-Encoding: base64\r\n\r\ndmFsdWU=\r\n------formdata-undici-0.5786922755719377--'
   const server = createServer((req, res) => {
-    res.setHeader('content-type', 'multipart/form-data')
+    res.setHeader('content-type', 'multipart/form-data; boundary=----formdata-undici-0.5786922755719377')
+    res.write(formRaw)
     res.end()
   })
   t.teardown(server.close.bind(server))
 
   server.listen(0, () => {
     fetch(`http://localhost:${server.address().port}`)
       .then(res => res.formData())
-      .catch(err => {
-        t.equal(err.name, 'NotSupportedError')
+      .then(form => form.get('key').text())
+      .then(text => {
+        t.equal(text, 'value')
       })
   })
 })
 
+test('busboy emit error', async (t) => {
+  t.plan(1)
+  const formData = new FormData()
+  formData.append('field1', 'value1')
+
+  const tempRes = new Response(formData)
+  const formRaw = await tempRes.text()
+
+  const server = createServer((req, res) => {
+    res.setHeader('content-type', 'multipart/form-data; boundary=wrongboundary')
+    res.write(formRaw)
+    res.end()
+  })
+  t.teardown(server.close.bind(server))
+
+  const listen = promisify(server.listen.bind(server))
+  await listen(0)
+
+  const res = await fetch(`http://localhost:${server.address().port}`)
+  await t.rejects(res.formData(), 'Unexpected end of multipart data')
+})
+
 test('urlencoded formData', (t) => {
   t.plan(2)