Accept third-party Blobs in FormData

nodejs · Nov 16, 2021 · bac3ee2 · bac3ee2
1 parent 64d07c3
commit bac3ee2
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Showing 2 changed files with 19 additions and 7 deletions.
diff --git a/lib/fetch/formdata.js b/lib/fetch/formdata.js
@@ -1,9 +1,8 @@
 'use strict'
 
-const { Blob } = require('buffer')
+const { isBlobLike, toUSVString } = require('./util')
 const { kState } = require('./symbols')
 const { File } = require('./file')
-const { toUSVString } = require('./util')
 
 class FormData {
   constructor (...args) {
@@ -25,7 +24,7 @@ class FormData {
         `Failed to execute 'append' on 'FormData': 2 arguments required, but only ${args.length} present.`
       )
     }
-    if (args.length === 3 && !(args[1] instanceof Blob)) {
+    if (args.length === 3 && !isBlobLike(args[1])) {
       throw new TypeError(
         "Failed to execute 'append' on 'FormData': parameter 2 is not of type 'Blob'"
       )
@@ -34,7 +33,7 @@ class FormData {
     const filename = args.length === 3 ? toUSVString(args[2]) : undefined
 
     // 1. Let value be value if given; otherwise blobValue.
-    const value = args[1] instanceof Blob ? args[1] : toUSVString(args[1])
+    const value = isBlobLike(args[1]) ? args[1] : toUSVString(args[1])
 
     // 2. Let entry be the result of creating an entry with
     // name, value, and filename if given.
@@ -135,7 +134,7 @@ class FormData {
         `Failed to execute 'set' on 'FormData': 2 arguments required, but only ${args.length} present.`
       )
     }
-    if (args.length === 3 && !(args[1] instanceof Blob)) {
+    if (args.length === 3 && !isBlobLike(args[1])) {
       throw new TypeError(
         "Failed to execute 'set' on 'FormData': parameter 2 is not of type 'Blob'"
       )
@@ -147,7 +146,7 @@ class FormData {
     // are:
 
     // 1. Let value be value if given; otherwise blobValue.
-    const value = args[1] instanceof Blob ? args[1] : toUSVString(args[1])
+    const value = isBlobLike(args[1]) ? args[1] : toUSVString(args[1])
 
     // 2. Let entry be the result of creating an entry with name, value, and
     // filename if given.
@@ -214,7 +213,7 @@ function makeEntry (name, value, filename) {
 
   // 3. If value is a Blob object and not a File object, then set value to a new File
   // object, representing the same bytes, whose name attribute value is "blob".
-  if (value instanceof Blob && !(value instanceof File)) {
+  if (isBlobLike(value) && !(value instanceof File)) {
     value = new File([value], 'blob')
   }
 

diff --git a/lib/fetch/util.js b/lib/fetch/util.js
@@ -68,6 +68,18 @@ function requestBadPort (request) {
   return 'allowed'
 }
 
+// based on https://github.com/node-fetch/fetch-blob/blob/8ab587d34080de94140b54f07168451e7d0b655e/index.js#L229-L241 (MIT License)
+function isBlobLike (object) {
+  return (
+    object &&
+    typeof object === 'object' &&
+    typeof object.constructor === 'function' &&
+    (typeof object.stream === 'function' ||
+      typeof object.arrayBuffer === 'function') &&
+    /^(Blob|File)$/.test(object[Symbol.toStringTag])
+  )
+}
+
 // Check whether |statusText| is a ByteString and
 // matches the Reason-Phrase token production.
 // RFC 2616: https://tools.ietf.org/html/rfc2616
@@ -349,5 +361,6 @@ module.exports = {
   requestCurrentURL,
   responseURL,
   responseLocationURL,
+  isBlobLike,
   isValidReasonPhrase
 }