fetch: update extractBody to better match spec (nodejs#1745)

lib/fetch/body.js

@@ -2,7 +2,7 @@
 
 const Busboy = require('busboy')
 const util = require('../core/util')
-const { ReadableStreamFrom, toUSVString, isBlobLike, isReadableStreamLike, readableStreamClose } = require('./util')
+const { ReadableStreamFrom, isBlobLike, isReadableStreamLike, readableStreamClose } = require('./util')
 const { FormData } = require('./formdata')
 const { kState } = require('./symbols')
 const { webidl } = require('./webidl')
@@ -66,9 +66,13 @@ function extractBody (object, keepalive = false) {
   let type = null
 
   // 10. Switch on object:
-  if (object == null) {
-    // Note: The IDL processor cannot handle this situation. See
-    // https://crbug.com/335871.
+  if (typeof object === 'string') {
+    // Set source to the UTF-8 encoding of object.
+    // Note: setting source to a Uint8Array here breaks some mocking assumptions.
+    source = object
+
+    // Set type to `text/plain;charset=UTF-8`.
+    type = 'text/plain;charset=UTF-8'
   } else if (object instanceof URLSearchParams) {
     // URLSearchParams
 
@@ -157,6 +161,11 @@ function extractBody (object, keepalive = false) {
     if (object.type) {
       type = object.type
     }
+  } else if (object instanceof Uint8Array) {
+    // byte sequence
+
+    // Set source to object.
+    source = object
   } else if (typeof object[Symbol.asyncIterator] === 'function') {
     // If keepalive is true, then throw a TypeError.
     if (keepalive) {
@@ -172,17 +181,10 @@ function extractBody (object, keepalive = false) {
 
     stream =
       object instanceof ReadableStream ? object : ReadableStreamFrom(object)
-  } else {
-    // TODO: byte sequence?
-    // TODO: scalar value string?
-    // TODO: else?
-    source = toUSVString(object)
-    type = 'text/plain;charset=UTF-8'
   }
 
   // 11. If source is a byte sequence, then set action to a
   // step that returns source and length to source’s length.
-  // TODO: What is a "byte sequence?"
   if (typeof source === 'string' || util.isBuffer(source)) {
     length = Buffer.byteLength(source)
   }