Do not guess File content-type when it was not present. This change was made for browsers compatibility reasons.

Author: octet-stream

lib/Encoder.test.ts

@@ -125,7 +125,9 @@ test("Yields Content-Disposition header for a File", async t => {
 test("Yields Content-Type header for a File", async t => {
   const fd = new FormData()
 
-  fd.set("file", new File(["My hovercraft is full of eels"], "file.txt"))
+  fd.set("file", new File(["My hovercraft is full of eels"], "file.txt"), {
+    type: "text/plain"
+  })
 
   const {value} = await skip(readLine(Readable.from(new Encoder(fd))), 3)
 
@@ -206,8 +208,14 @@ test("Yields every appended File", async t => {
 
   const fd = new FormData()
 
-  fd.append("file", new File(["Some content"], "file.txt"))
-  fd.append("file", new File(["Some **content**"], "file.md"))
+  const firstFile = new File(["Some content"], "file.txt", {type: "text/plain"})
+  const secondFile = new File(["Some **content**"], "file.md", {
+    type: "text/markdown"
+  })
+
+  fd.append("file", firstFile)
+
+  fd.append("file", secondFile)
 
   const iterable = readLine(Readable.from(new Encoder(fd)))
 
@@ -221,7 +229,7 @@ test("Yields every appended File", async t => {
 
   const {value: firstFileContent} = await skip(iterable, 2)
 
-  t.is(firstFileContent, "Some content")
+  t.is(firstFileContent, await firstFile.text())
 
   const {value: secondFileDisposition} = await skip(iterable, 2)
 
@@ -233,7 +241,7 @@ test("Yields every appended File", async t => {
 
   const {value: secondFileContent} = await skip(iterable, 2)
 
-  t.is(secondFileContent, "Some **content**")
+  t.is(secondFileContent, await secondFile.text())
 })
 
 test("Can be used with ReadableStream", async t => {

lib/Encoder.ts

@@ -1,5 +1,4 @@
 import createBoundary from "./util/createBoundary"
-import getMime from "./util/getMimeFromFilename"
 import isFormData from "./util/isFormData"
 import isFile from "./util/isFile"
 
@@ -98,7 +97,7 @@ export class Encoder {
 
     if (isFile(value)) {
       header += `; filename="${value.name}"${this.#CRLF}`
-      header += `Content-Type: ${value.type || getMime(value.name)}`
+      header += `Content-Type: ${value.type || "application/octet-stream"}`
     }
 
     return this.#encoder.encode(`${header}${this.#CRLF.repeat(2)}`)

lib/util/getMimeFromFilename.ts

@@ -58,8 +58,5 @@
     "ttypescript": "1.5.12",
     "typescript": "4.2.4",
     "web-streams-polyfill": "3.0.3"
-  },
-  "dependencies": {
-    "mime-types": "2.1.30"
   }
 }