fix: allow third party AbortControllers

lib/fetch/request.js

@@ -835,6 +835,10 @@ webidl.converters.RequestInfo = function (V) {
   return webidl.converters.USVString(V)
 }
 
+webidl.converters.AbortSignal = webidl.interfaceConverter(
+  AbortSignal
+)
+
 // https://fetch.spec.whatwg.org/#requestinit
 webidl.converters.RequestInit = webidl.dictionaryConverter([
   {
@@ -909,7 +913,12 @@ webidl.converters.RequestInit = webidl.dictionaryConverter([
   },
   {
     key: 'signal',
-    converter: webidl.converters.any
+    converter: webidl.nullableConverter(
+      (signal) => webidl.converters.AbortSignal(
+        signal,
+        { strict: false }
+      )
+    )
   },
   {
     key: 'window',

test/fetch/request.js

@@ -5,7 +5,8 @@
 const { test } = require('tap')
 const {
   Request,
-  Headers
+  Headers,
+  fetch
 } = require('../../')
 const { kState } = require('../../lib/fetch/symbols.js')
 const hasSignalReason = !!~process.version.localeCompare('v16.14.0', undefined, { numeric: true })
@@ -421,3 +422,16 @@ test('invalid RequestInit values', (t) => {
 
   t.end()
 })
+
+test('RequestInit.signal option', async (t) => {
+  t.throws(() => {
+    // eslint-disable-next-line no-new
+    new Request('http://asd', {
+      signal: true
+    })
+  }, TypeError)
+
+  await t.rejects(fetch('http://asd', {
+    signal: false
+  }), TypeError)
+})