Add tests for FormDataLike and FileLike compatibility

package.json

@@ -70,15 +70,18 @@
     "eslint-plugin-import": "2.27.5",
     "eslint-plugin-jsx-a11y": "6.7.1",
     "eslint-plugin-react": "7.32.2",
-    "formdata-node": "5.0.0",
+    "formdata-node": "6.0.2",
     "husky": "8.0.3",
     "lint-staged": "13.2.2",
+    "node-fetch": "^3.3.2",
     "pinst": "3.0.0",
     "sinon": "15.0.4",
+    "ts-expect": "^1.3.0",
     "ts-node": "10.9.1",
     "tsup": "7.2.0",
     "ttypescript": "1.5.15",
     "typescript": "5.0.4",
+    "undici": "^5.26.5",
     "web-streams-polyfill": "4.0.0-beta.3"
   }
 }

src/FileLike.test.ts

@@ -0,0 +1,32 @@
+import test from "ava"
+
+import {expectType} from "ts-expect"
+import {File as FormDataNodeFile} from "formdata-node"
+import {File as NodeFetchFile} from "node-fetch"
+import {File as UndiciFile} from "undici"
+
+import type {FileLike} from "./FileLike.js"
+
+test("File is assignable to FileLike", t => {
+  expectType<FileLike>(new File([], "test.txt"))
+
+  t.pass()
+})
+
+test("File from formdata-node is assignable to FileLike", t => {
+  expectType<FileLike>(new FormDataNodeFile([], "test.txt"))
+
+  t.pass()
+})
+
+test("File from undici is assignable to FileLike", t => {
+  expectType<FileLike>(new UndiciFile([], "test.txt"))
+
+  t.pass()
+})
+
+test("File from node-fetch is assignable to FileLike", t => {
+  expectType<FileLike>(new NodeFetchFile([], "test.txt"))
+
+  t.pass()
+})

src/FileLike.ts

@@ -22,7 +22,7 @@ export interface FileLike {
   /**
    * Returns a [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) which upon reading returns the data contained within the [`File`](https://developer.mozilla.org/en-US/docs/Web/API/File).
    */
-  stream(): AsyncIterable<Uint8Array>
+  stream(): ReadableStream<Uint8Array> | AsyncIterable<Uint8Array>
 
-  readonly [Symbol.toStringTag]: string
+  readonly [Symbol.toStringTag]?: string
 }

src/FormDataLike.test.ts

@@ -0,0 +1,32 @@
+import test from "ava"
+
+import {expectType} from "ts-expect"
+import {FormData as FormDataNode} from "formdata-node"
+import {FormData as NodeFetchFormData} from "node-fetch"
+import {FormData as UndiciFormData} from "undici"
+
+import type {FormDataLike} from "./FormDataLike.js"
+
+test("FormData is assignable to FormDataLike", t => {
+  expectType<FormDataLike>(new FormData())
+
+  t.pass()
+})
+
+test("FormData from formdata-node is assignable to FormDataLike", t => {
+  expectType<FormDataLike>(new FormDataNode())
+
+  t.pass()
+})
+
+test("FormData from undici is assignable to FormDataLike", t => {
+  expectType<FormDataLike>(new UndiciFormData())
+
+  t.pass()
+})
+
+test("FormData from node-fetch is assignable to FormDataLike", t => {
+  expectType<FormDataLike>(new NodeFetchFormData())
+
+  t.pass()
+})

src/FormDataLike.ts

@@ -42,5 +42,5 @@ export interface FormDataLike {
    */
   [Symbol.iterator](): IterableIterator<[string, FormDataEntryValue]>
 
-  readonly [Symbol.toStringTag]: string
+  readonly [Symbol.toStringTag]?: string
 }

src/util/isFile.test.ts

@@ -21,7 +21,7 @@ test("Returns true for a class that implements File", t => {
 
     lastModified = Date.now()
 
-    async* stream(): AsyncGenerator<Uint8Array> {
+    async* stream(): AsyncIterable<Uint8Array> {
       yield new Uint8Array(0)
     }