HTTP Headers can't be stored in a HashMap

[crazytonyli]

To track this TODO

wordpress-rs/wp_api/src/request.rs

Lines 62 to 67 in 2b572dd

	// TODO: We probably want to implement a specific type for these headers instead of using a
	// regular HashMap.
	//
	// It could be something similar to `reqwest`'s [`header`](https://docs.rs/reqwest/latest/reqwest/header/index.html)
	// module.
	pub header_map: Option<HashMap<String, String>>,

---

HashMap is not suitable for storing HTTP headers, since header name can repeat. For example, HTTP responses can contain multiple Link headers:

Finally, this header field:

Link: https://example.org/; rel="start",
https://example.org/index; rel="index"

is equivalent to these:

Link: https://example.org/; rel="start"
Link: https://example.org/index; rel="index"

[crazytonyli]

FWIW, Apple's URLSession merges repeated headers into one. So using a HashMap shouldn't cause any issue on Apple platforms.

Take longreads.com as an exmpale.

Here are all the headers:

$ curl -sI 'https://longreads.com'
HTTP/2 200
server: nginx
date: Thu, 30 May 2024 04:31:40 GMT
content-type: text/html; charset=UTF-8
strict-transport-security: max-age=31536000
vary: Accept-Encoding
last-modified: Thu, 30 May 2024 04:28:31 GMT
cache-control: max-age=268, must-revalidate
x-nananana: Batcache-Hit
host-header: Newspack
vary: accept, content-type, cookie
link: <https://longreads.com/wp-json/>; rel="https://api.w.org/"
link: <https://longreads.com/wp-json/wp/v2/pages/157302>; rel="alternate"; type="application/json"
link: <https://longreads.com/>; rel=shortlink
x-ac: 2.syd _atomic_bur HIT
alt-svc: h3=":443"; ma=86400

Note there are multiple "link" headers.

When using URLSession to perform HTTP request, those link headers are merged into one:

I used this code to print all headers

let (_, response) = try await URLSession.shared.data(from: URL(string: "https://longreads.com")!)
for (name, value) in (response as! HTTPURLResponse).allHeaderFields {
    print("\(name): \(value)")
}

And, the result is

x-nananana: Batcache-Hit
Link: <https://longreads.com/wp-json/>; rel="https://api.w.org/", <https://longreads.com/wp-json/wp/v2/pages/157302>; rel="alternate"; type="application/json", <https://longreads.com/>; rel=shortlink
Last-Modified: Thu, 30 May 2024 04:13:16 GMT
Strict-Transport-Security: max-age=31536000
Date: Thu, 30 May 2024 04:28:27 GMT
host-header: Newspack
Alt-Svc: clear
Vary: Accept-Encoding, accept, content-type, cookie
x-ac: 2.syd _atomic_bur STALE
Cache-Control: max-age=226, must-revalidate
Server: nginx
Content-Encoding: br
Content-Type: text/html; charset=UTF-8

[crazytonyli]

However, header names are case-insensitive. WpNetworkResponse.header_map.get("link") should return the same value as get("Link"), which I don't think is the case at the moment.

[oguzkocer]

Re-opening this issue since the PR is being reverted in #135.

[oguzkocer]

Addressed in #160.