Impossible to provide a `RequestInit` with fetch

[sdeleuze]

In my sample application with Kotlin/Wasm 2.1.21 , window.fetch(url) works as expected, but window.fetch(url, RequestInit(method = "POST")) throws the following error:

sample-wasm-js.uninstantiated.mjs:150 Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'Window': Failed to read the 'cache' property from 'RequestInit': The provided value 'null' is not a valid enum value of type RequestCache.
    at org.w3c.dom.fetch_$external_fun (sample-wasm-js.uninstantiated.mjs:150:82)
    at 04d61904f8aaba159022.wasm:0x35d09
    at 04d61904f8aaba159022.wasm:0x34d5c
    at HTMLFormElement.<anonymous> (sample-wasm-js.uninstantiated.mjs:142:127)

If I change to window.fetch(url, RequestInit(method = "POST", cache = RequestCache.Companion.DEFAULT)), I get:

sample-wasm-js.uninstantiated.mjs:150 Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'Window': Failed to read the 'credentials' property from 'RequestInit': The provided value 'null' is not a valid enum value of type RequestCredentials.
    at org.w3c.dom.fetch_$external_fun (sample-wasm-js.uninstantiated.mjs:150:82)
    at ba229722ec51e8dd8a68.wasm:0x35d74
    at ba229722ec51e8dd8a68.wasm:0x34d9d
    at HTMLFormElement.<anonymous> (sample-wasm-js.uninstantiated.mjs:142:127)
org.w3c.dom.fetch_$external_fun @ sample-wasm-js.uninstantiated.mjs:150
$func1542 @ ba229722ec51e8dd8a68.wasm:0x35d74
$__callFunction___Js_->Unit_ @ ba229722ec51e8dd8a68.wasm:0x34d9d
(anonymous) @ sample-wasm-js.uninstantiated.mjs:142

If I change to window.fetch(url, RequestInit(method = "POST", cache = RequestInit(method = "POST", cache = RequestCache.Companion.DEFAULT, credentials = RequestCredentials.Companion.OMIT)), I get:

sample-wasm-js.uninstantiated.mjs:150 Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'Window': Failed to read the 'headers' property from 'RequestInit': The provided value is not of type '(record<ByteString, ByteString> or sequence<sequence<ByteString>>)'.
    at org.w3c.dom.fetch_$external_fun (sample-wasm-js.uninstantiated.mjs:150:82)
    at 99192d8e1d750b4a96d2.wasm:0x35de7
    at 99192d8e1d750b4a96d2.wasm:0x34dfc
    at HTMLFormElement.<anonymous> (sample-wasm-js.uninstantiated.mjs:142:127)
org.w3c.dom.fetch_$external_fun @ sample-wasm-js.uninstantiated.mjs:150
$func1544 @ 99192d8e1d750b4a96d2.wasm:0x35de7
$__callFunction___Js_->Unit_ @ 99192d8e1d750b4a96d2.wasm:0x34dfc
(anonymous) @ sample-wasm-js.uninstantiated.mjs:142

Please allows to specify RequestInit with just some properties defined.

[bashor]

Hi! Thanks for the report!

Looks like a bug in RequestInit implementation, as workaround you can define own version, something like:

public fun RequestInit(
    method: String? = null,
    headers: JsAny? /* Headers|JsArray<JsArray<JsString>>|OpenEndedDictionary<JsString> */ = null,
    body: JsAny? /* Blob|BufferSource|FormData|URLSearchParams|String */ = null,
    referrer: String? = null,
    referrerPolicy: JsAny? = null,
    mode: RequestMode? = null,
    credentials: RequestCredentials? = null,
    cache: RequestCache? = null,
    redirect: RequestRedirect? = null,
    integrity: String? = null,
    keepalive: Boolean? = null,
    window: JsAny? = null
): RequestInit {
    js("""
        const obj = {};

        if (method) obj.method = method;
        if (headers) obj.headers = headers;
        if (body) obj.body = body;
        if (referrer) obj.referrer = referrer;
        if (referrerPolicy) obj.referrerPolicy = referrerPolicy;
        if (mode) obj.mode = mode;
        if (credentials) obj.credentials = credentials;
        if (cache) obj.cache = cache;
        if (redirect) obj.redirect = redirect;
        if (integrity) obj.integrity = integrity;
        if (keepalive) obj.keepalive = keepalive;
        if (window) obj.window = window;
        
        return obj;
        """)
}