Add tests for isFile and isFormData helpers. Loosen isFormData helper.

Author: octet-stream

lib/FileLike.ts

@@ -7,7 +7,7 @@ export interface FileLike {
 
   lastModified: number
 
-  stream(): {[Symbol.asyncIterator](): AsyncIterableIterator<any>}
+  stream(): {[Symbol.asyncIterator](): AsyncIterableIterator<Uint8Array>}
 
   [Symbol.toStringTag]: string
 }

lib/FormDataLike.ts

@@ -1,27 +1,21 @@
 import {FileLike} from "./FileLike"
 
+/**
+ * This interface reflects possible values of each FormData entry
+ */
 export type FormDataEntryValue = string | FileLike
 
+/**
+ * This interface reflects minimal shape of the FormData
+ */
 export interface FormDataLike {
-  set(name: string, value: unknown): void
+  append(name: string, value: unknown, filename?: string): void
 
-  append(name: string, value: unknown): void
+  getAll(name: string): FormDataEntryValue[]
 
-  has(name: string): boolean
+  entries(): Generator<[string, FormDataEntryValue]>
 
-  get(name: string): null | FormDataEntryValue
-
-  getAll(name: string): Array<null | FormDataEntryValue>
-
-  delete(name: string): void
-
-  keys(): IterableIterator<string>
-
-  values(): IterableIterator<FormDataEntryValue>
-
-  entries(): IterableIterator<[string, FormDataEntryValue]>
-
-  [Symbol.iterator](): IterableIterator<[string, FormDataEntryValue]>
+  [Symbol.iterator](): Generator<[string, FormDataEntryValue]>
 
   [Symbol.toStringTag]: string
 }

lib/util/isFile.ts

@@ -5,7 +5,9 @@ import {FileLike} from "../FileLike"
 const VALID_NAMES = ["File", "Blob"]
 
 /**
- * Check if given object is File
+ * Check if given object is File.
+ *
+ * Note that this function will return "false" for Blob, because the Encoder expects FormData to return File when a value is binary data.
  *
  * @param value an object to test
  */
@@ -15,6 +17,9 @@ const isFile = (value?: unknown): value is FileLike => Boolean(
     && isFunction((value as FileLike).constructor)
     && VALID_NAMES.includes((value as FileLike)[Symbol.toStringTag])
     && isFunction((value as FileLike).stream)
+    && (value as FileLike).name != null
+    && (value as FileLike).size != null
+    && (value as FileLike).lastModified != null
 )
 
 export default isFile

lib/util/isFormData.test.ts

@@ -4,10 +4,60 @@ import {FormData} from "formdata-node"
 
 import isFormData from "./isFormData"
 
+import {FormDataLike, FormDataEntryValue} from "../FormDataLike"
+
 test("Returns true for spec-compatible FormData instance", t => {
   t.true(isFormData(new FormData()))
 })
 
+test("Returns true for a class that implements minimal FormData", t => {
+  class MyFormData implements FormDataLike {
+    append(): void {}
+
+    getAll(): FormDataEntryValue[] {
+      return []
+    }
+
+    * entries(): Generator<[string, FormDataEntryValue]> {
+      yield ["name", "value"]
+    }
+
+    [Symbol.iterator]() {
+      return this.entries()
+    }
+
+    get [Symbol.toStringTag](): string {
+      return "FormData"
+    }
+  }
+
+  t.true(isFormData(new MyFormData()))
+})
+
+test("Returns true for FormData-shaped object", t => {
+  const object = {
+    append(): void {},
+
+    getAll(): FormDataEntryValue[] {
+      return []
+    },
+
+    * entries(): Generator<[string, FormDataEntryValue]> {
+      yield ["name", "value"]
+    },
+
+    [Symbol.iterator]() {
+      return this.entries()
+    },
+
+    get [Symbol.toStringTag](): string {
+      return "FormData"
+    }
+  }
+
+  t.true(isFormData(object))
+})
+
 test("Returns false for null", t => {
   t.false(isFormData(null))
 })

lib/util/isFormData.ts

@@ -11,13 +11,8 @@ const isFormData = (value?: unknown): value is FormDataLike => Boolean(
   (value as FormDataLike)
     && isFunction((value as FormDataLike).constructor)
     && (value as FormDataLike)[Symbol.toStringTag] === "FormData"
-    && isFunction((value as FormDataLike).set)
     && isFunction((value as FormDataLike).append)
-    && isFunction((value as FormDataLike).has)
-    && isFunction((value as FormDataLike).get)
     && isFunction((value as FormDataLike).getAll)
-    && isFunction((value as FormDataLike).keys)
-    && isFunction((value as FormDataLike).values)
     && isFunction((value as FormDataLike).entries)
     && isFunction((value as FormDataLike)[Symbol.iterator])
 )