MockAgent unexpected multi header behaviour with fetch #2616
Description
First of all thank you for maintaining this library ❤️
Bug Description
I encountered an unexpected behaviour when using fetch with multi value headers via MockAgent.
I would expect the behaviour from fetch to be the same when using request (reference test) with MockAgent.
Is this behaviour expected and I am just missing something?
Reproducible By
save the following content as test/repro.js in the undici repository and then run npx tap test/repro.js
'use strict'
const { test } = require('tap')
const { setGlobalDispatcher, MockAgent } = require('..')
const { fetch } = require('..')
test("MockAgent - headers should be array of strings (fetch)", async (t) => {
const mockAgent = new MockAgent();
mockAgent.disableNetConnect();
setGlobalDispatcher(mockAgent);
const mockPool = mockAgent.get("http://localhost:3000");
mockPool
.intercept({
path: "/foo",
method: "GET",
})
.reply(200, "foo", {
headers: {
"set-cookie": ["foo=bar", "bar=baz", "baz=qux"],
},
});
const { headers } = await fetch("http://localhost:3000/foo", {
method: "GET",
});
t.equal(headers.getSetCookie(), ["foo=bar", "bar=baz", "baz=qux"]);
});Expected Behavior
headers.getSetCookie() should return an array (["foo=bar", "bar=baz", "baz=qux"]) but instead it just returns ["foo=bar,bar=baz,baz=qux"] (array with one entry and all values concatenated)
Logs & Screenshots
FAIL test/repro.js
✖ should be equal
test/repro.js
27 | });
28 |
> 29 | t.equal(headers.getSetCookie(), ["foo=bar", "bar=baz", "baz=qux"]);
| ----^
30 | });
--- expected
+++ actual
@@ -1,5 +1,3 @@
Array [
- "foo=bar",
- "bar=baz",
- "baz=qux",
+ "foo=bar,bar=baz,baz=qux",
]
test: test/repro.js MockAgent - headers should be array of strings (fetch)
Environment
Node v20.11.0ubuntu-22.04