Backport fix for browsers compatibility

Author: octet-stream

lib/FormDataEncoder.ts

@@ -1,5 +1,6 @@
 /* eslint-disable no-restricted-globals */
 
+import getStreamIterator from "./util/getStreamIterator"
 import createBoundary from "./util/createBoundary"
 import isPlainObject from "./util/isPlainObject"
 import normalize from "./util/normalizeValue"
@@ -319,7 +320,7 @@ export class FormDataEncoder {
   async* encode(): AsyncGenerator<Uint8Array, void, undefined> {
     for (const part of this.values()) {
       if (isFileLike(part)) {
-        yield* part.stream()
+        yield* getStreamIterator(part.stream())
       } else {
         yield part
       }

lib/util/getStreamIterator.test.ts

@@ -0,0 +1,62 @@
+import test from "ava"
+
+import {ReadableStream} from "web-streams-polyfill"
+import {stub} from "sinon"
+
+import getStreamIterator from "./getStreamIterator"
+
+test(
+  "Returns readable stream as is, if it implements Symbol.asyncIterator",
+
+  t => {
+    const stream = new ReadableStream()
+
+    t.is(getStreamIterator(stream), stream)
+  }
+)
+
+test(
+  "Returns fallback when given stream does not implement Symbol.asyncIterator",
+
+  t => {
+    const stream = new ReadableStream()
+
+    stub(stream, Symbol.asyncIterator).get(() => undefined)
+
+    t.false(getStreamIterator(stream) instanceof ReadableStream)
+  }
+)
+
+test("Reads from the stream using fallback", async t => {
+  const expected = "Some text"
+
+  const stream = new ReadableStream({
+    pull(controller) {
+      controller.enqueue(new TextEncoder().encode(expected))
+      controller.close()
+    }
+  })
+
+  stub(stream, Symbol.asyncIterator).get(() => undefined)
+
+  let actual = ""
+  const decoder = new TextDecoder()
+  for await (const chunk of getStreamIterator(stream)) {
+    actual += decoder.decode(chunk, {stream: true})
+  }
+
+  actual += decoder.decode()
+
+  t.is(actual, expected)
+})
+
+test("Throws TypeError for unsupported data sources", t => {
+  // @ts-expect-error
+  const trap = () => getStreamIterator({})
+
+  t.throws(trap, {
+    instanceOf: TypeError,
+    message: "Unsupported data source: Expected either "
+      + "ReadableStream or async iterable."
+  })
+})

lib/util/getStreamIterator.ts

@@ -0,0 +1,55 @@
+import isFunction from "./isFunction"
+
+/**
+ * Checks if the value is async iterable
+ */
+const isAsyncIterable = (
+  value: unknown
+): value is AsyncIterable<Uint8Array> => (
+  isFunction((value as AsyncIterable<Uint8Array>)[Symbol.asyncIterator])
+)
+
+/**
+ * Reads from given ReadableStream
+ *
+ * @param readable A ReadableStream to read from
+ */
+async function* readStream(
+  readable: ReadableStream<Uint8Array>
+): AsyncGenerator<Uint8Array, void, undefined> {
+  const reader = readable.getReader()
+
+  while (true) {
+    const {done, value} = await reader.read()
+
+    if (done) {
+      break
+    }
+
+    yield value
+  }
+}
+
+/**
+ * Turns ReadableStream into async iterable when the `Symbol.asyncIterable` is not implemented on given stream.
+ *
+ * @param source A ReadableStream to create async iterator for
+ */
+const getStreamIterator = (
+  source: ReadableStream<Uint8Array> | AsyncIterable<Uint8Array>
+): AsyncIterable<Uint8Array> => {
+  if (isAsyncIterable(source)) {
+    return source
+  }
+
+  if (isFunction(source.getReader)) {
+    return readStream(source)
+  }
+
+  // Throw an error otherwise (for example, in case if encountered Node.js Readable stream without Symbol.asyncIterator method)
+  throw new TypeError(
+    "Unsupported data source: Expected either ReadableStream or async iterable."
+  )
+}
+
+export default getStreamIterator

package.json

@@ -41,6 +41,7 @@
     "@octetstream/eslint-config": "5.0.0",
     "@types/mime-types": "2.1.1",
     "@types/node": "17.0.25",
+    "@types/sinon": "^10.0.13",
     "@typescript-eslint/eslint-plugin": "4.33.0",
     "@typescript-eslint/parser": "4.33.0",
     "@zoltu/typescript-transformer-append-js-extension": "1.0.1",
@@ -56,8 +57,10 @@
     "husky": "7.0.4",
     "lint-staged": "12.4.0",
     "pinst": "2.1.6",
+    "sinon": "14.0.2",
     "ts-node": "10.7.0",
     "ttypescript": "1.5.13",
-    "typescript": "4.6.3"
+    "typescript": "4.6.3",
+    "web-streams-polyfill": "4.0.0-beta.3"
   }
 }