script/fetch/

fetch.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

#![cfg_attr(crown, allow(crown::jscontext_first_arg))]

use std::cell::Cell;
use std::rc::Rc;
use std::time::Duration;

use bytes::Bytes;
use js::context::JSContext;
use js::gc::Rootable;
use js::jsapi::ExceptionStackBehavior;
use js::jsval::UndefinedValue;
use js::realm::CurrentRealm;
use js::rust::HandleValue;
use net_traits::blob_url_store::UrlWithBlobClaim;
use net_traits::fetch::fetch_controller::FetchController;
use net_traits::request::{
    CorsSettings, CredentialsMode, Destination, Referrer, Request as NetTraitsRequest,
    RequestBuilder, RequestId, RequestMode, ServiceWorkersMode,
};
use net_traits::{
    CoreResourceMsg, CoreResourceThread, FetchChannels, FetchMetadata, FetchResponseMsg,
    FilteredMetadata, Metadata, NetworkError, ResourceFetchTiming, fetch_async,
};
use rustc_hash::FxHashMap;
use script_bindings::cformat;
use script_bindings::js::{JS_IsExceptionPending, JS_SetPendingException};
use script_bindings::root::Dom;
use serde::{Deserialize, Serialize};
use servo_base::generic_channel::GenericCallback;
use servo_base::id::WebViewId;
use servo_url::ServoUrl;
use timers::TimerEventRequest;
use uuid::Uuid;

use crate::dom::TracedPromise;
use crate::dom::abortsignal::AbortAlgorithm;
use crate::dom::bindings::codegen::Bindings::AbortSignalBinding::AbortSignalMethods;
use crate::dom::bindings::codegen::Bindings::RequestBinding::{
    RequestInfo, RequestInit, RequestMethods,
};
use crate::dom::bindings::codegen::Bindings::ResponseBinding::Response_Binding::ResponseMethods;
use crate::dom::bindings::codegen::Bindings::ResponseBinding::ResponseType as DOMResponseType;
use crate::dom::bindings::codegen::Bindings::WindowBinding::{DeferredRequestInit, WindowMethods};
use crate::dom::bindings::error::{Error, Fallible};
use crate::dom::bindings::inheritance::Castable;
use crate::dom::bindings::num::Finite;
use crate::dom::bindings::refcounted::Trusted;
use crate::dom::bindings::root::DomRoot;
use crate::dom::bindings::trace::NoTrace;
use crate::dom::csp::{GlobalCspReporting, Violation};
use crate::dom::fetchlaterresult::FetchLaterResult;
use crate::dom::globalscope::GlobalScope;
use crate::dom::headers::Guard;
use crate::dom::performance::performanceresourcetiming::InitiatorType;
use crate::dom::promise::{Promise, RootedPromise};
use crate::dom::request::Request;
use crate::dom::response::Response;
use crate::dom::serviceworkerglobalscope::ServiceWorkerGlobalScope;
use crate::dom::window::Window;
use crate::fetch::body::BodyMixin;
use crate::fetch::network_listener::{
    self, FetchResponseListener, NetworkListener, ResourceTimingListener, submit_timing_data,
};
use crate::realms::enter_auto_realm;

/// An id to differentiate one deferred fetch record from another.
#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]
pub(crate) struct DeferredFetchRecordId(Uuid);

impl Default for DeferredFetchRecordId {
    fn default() -> Self {
        Self(Uuid::new_v4())
    }
}

pub(crate) type QueuedDeferredFetchRecord = Rc<DeferredFetchRecord>;

/// <https://fetch.spec.whatwg.org/#fetch-record>
#[derive(JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) struct FetchRecord {
    /// <https://fetch.spec.whatwg.org/#concept-fetch-record-fetch>
    #[no_trace]
    controller: Option<FetchController>,
    /// If this record was created by a call to `fetch()`, this holds the [`Request`]
    /// that started this operation.
    request: Option<Dom<Request>>,
}

/// <https://fetch.spec.whatwg.org/#concept-fetch-group>
#[derive(JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) struct FetchGroup {
    /// The [`CoreResourceThread`] for this [`FetchGroup`].
    #[no_trace]
    core_resource_thread: CoreResourceThread,
    /// <https://fetch.spec.whatwg.org/#fetch-group-deferred-fetch-records>
    #[conditional_malloc_size_of]
    #[no_trace]
    pub(crate) deferred_fetch_records: FxHashMap<DeferredFetchRecordId, QueuedDeferredFetchRecord>,
    /// <https://fetch.spec.whatwg.org/#concept-fetch-record>
    pub(crate) fetch_records: FxHashMap<NoTrace<RequestId>, FetchRecord>,
}

impl FetchGroup {
    pub(crate) fn new(core_resource_thread: CoreResourceThread) -> Self {
        Self {
            core_resource_thread,
            deferred_fetch_records: Default::default(),
            fetch_records: Default::default(),
        }
    }

    pub(crate) fn fetch<Listener: FetchResponseListener>(
        &mut self,
        request: RequestBuilder,
        listener: NetworkListener<Listener>,
        request_object: Option<&Request>,
    ) {
        self.fetch_records.insert(
            NoTrace(request.id),
            FetchRecord {
                controller: Some(FetchController::new(
                    request.id,
                    request.keep_alive,
                    self.core_resource_thread.clone(),
                )),
                request: request_object.map(Dom::from_ref),
            },
        );
        fetch_async(
            &self.core_resource_thread,
            request,
            None,
            listener.into_callback(),
        );
    }

    pub(crate) fn deferred_fetches(&self) -> Vec<QueuedDeferredFetchRecord> {
        self.deferred_fetch_records.values().cloned().collect()
    }

    fn append_deferred_fetch(
        &mut self,
        deferred_record: DeferredFetchRecord,
    ) -> DeferredFetchRecordId {
        let deferred_fetch_record_id = DeferredFetchRecordId::default();
        self.deferred_fetch_records
            .insert(deferred_fetch_record_id, Rc::new(deferred_record));
        deferred_fetch_record_id
    }

    pub(crate) fn deferred_fetch_record_for_id(
        &self,
        deferred_fetch_record_id: &DeferredFetchRecordId,
    ) -> QueuedDeferredFetchRecord {
        self.deferred_fetch_records
            .get(deferred_fetch_record_id)
            .expect("Should always use a generated fetch_record_id instead of passing your own")
            .clone()
    }

    pub(crate) fn fetch_controller(
        &mut self,
        request_id: &RequestId,
    ) -> Option<&mut FetchController> {
        self.fetch_records
            .get_mut(&NoTrace(*request_id))?
            .controller
            .as_mut()
    }

    pub(crate) fn fetch_call_request(&self, request_id: &RequestId) -> Option<DomRoot<Request>> {
        let fetch_record = self.fetch_records.get(&NoTrace(*request_id))?;
        let request = fetch_record.request.as_ref()?;
        Some(request.as_rooted())
    }

    /// <https://fetch.spec.whatwg.org/#concept-fetch-group-terminate>
    ///
    /// Returns `true` if any fetches were cancelled and `false` otherwise.
    pub(crate) fn terminate(&mut self, global: &GlobalScope) -> bool {
        // Step 1. For each fetch record record of fetchGroup’s fetch records,
        // if record’s controller is non-null and record’s request’s done flag
        // is unset and keepalive is false, terminate record’s controller.
        //
        // Fetches that are done are removed from our set of fetch records as soon as they finish,
        // so they do not need to be skipped here. This approach differs from the specification
        // text, but is behaviorally identical.
        let mut cancelled_any = false;
        self.fetch_records.retain(|_, fetch_record| {
            let Some(controller) = fetch_record.controller.as_mut() else {
                return false;
            };
            if !controller.keep_alive() {
                controller.terminate();
                cancelled_any = true;
                return false;
            }
            true
        });

        // Step 2. Process deferred fetches for fetchGroup.
        self.process_deferred_fetches(global);

        cancelled_any
    }

    /// <https://fetch.spec.whatwg.org/#process-deferred-fetches>
    pub(crate) fn process_deferred_fetches(&mut self, global: &GlobalScope) {
        // Step 1. For each deferred fetch record deferredRecord of fetchGroup’s
        // deferred fetch records, process a deferred fetch deferredRecord.
        for deferred_fetch in self.deferred_fetches() {
            self.process_a_deferred_fetch(global, &deferred_fetch);
        }
    }

    /// <https://fetch.spec.whatwg.org/#process-a-deferred-fetch>
    pub(crate) fn process_a_deferred_fetch(
        &mut self,
        global: &GlobalScope,
        deferred_fetch: &DeferredFetchRecord,
    ) {
        // Step 1. If deferredRecord’s invoke state is not "pending", then return.
        if deferred_fetch.invoke_state.get() != DeferredFetchRecordInvokeState::Pending {
            return;
        }
        // Step 2. Set deferredRecord’s invoke state to "sent".
        deferred_fetch
            .invoke_state
            .set(DeferredFetchRecordInvokeState::Sent);
        // Step 3. Fetch deferredRecord’s request.
        let fetch_later_listener = FetchLaterListener {
            url: deferred_fetch.request.url(),
        };
        let task_source = global.task_manager().networking_task_source().to_sendable();
        self.fetch(
            request_init_from_request(deferred_fetch.request.clone(), global),
            NetworkListener::new(fetch_later_listener, task_source),
            None, /* state */
        );
        // Step 4 is handled by caller
    }

    pub(crate) fn mark_fetch_request_as_done(&mut self, request_id: &RequestId) {
        self.fetch_records.remove(&NoTrace(*request_id));
    }
}

fn request_init_from_request(request: NetTraitsRequest, global: &GlobalScope) -> RequestBuilder {
    let mut builder = RequestBuilder::new(
        request.target_webview_id,
        request.url_with_blob_claim(),
        request.referrer,
    )
    .method(request.method)
    .headers(request.headers)
    .unsafe_request(request.unsafe_request)
    .body(request.body)
    .destination(request.destination)
    .synchronous(request.synchronous)
    .mode(request.mode)
    .cache_mode(request.cache_mode)
    .use_cors_preflight(request.use_cors_preflight)
    .credentials_mode(request.credentials_mode)
    .use_url_credentials(request.use_url_credentials)
    .referrer_policy(request.referrer_policy)
    .pipeline_id(request.pipeline_id)
    .redirect_mode(request.redirect_mode)
    .integrity_metadata(request.integrity_metadata)
    .cryptographic_nonce_metadata(request.cryptographic_nonce_metadata)
    .parser_metadata(request.parser_metadata)
    .initiator(request.initiator)
    .client(global.request_client(None))
    .response_tainting(request.response_tainting);
    builder.id = request.id;
    builder.reload_navigation = request.reload_navigation;
    builder.history_navigation = request.history_navigation;
    builder
}

/// <https://fetch.spec.whatwg.org/#abort-fetch>
fn abort_fetch_call(
    promise: &RootedPromise,
    request: &Request,
    response_object: Option<&Response>,
    abort_reason: HandleValue,
    global: &GlobalScope,
    cx: &mut JSContext,
) {
    // Step 1. Reject promise with error.
    promise.reject(cx, abort_reason);
    // Step 2. If request’s body is non-null and is readable, then cancel request’s body with error.
    if let Some(body) = request.body() &&
        body.is_readable()
    {
        body.cancel(cx, global, abort_reason);
    }
    // Step 3. If responseObject is null, then return.
    // Step 4. Let response be responseObject’s response.
    let Some(response) = response_object else {
        return;
    };
    // Step 5. If response’s body is non-null and is readable, then error response’s body with error.
    if let Some(body) = response.body() &&
        body.is_readable()
    {
        body.error(cx, abort_reason);
    }
}

/// <https://fetch.spec.whatwg.org/#dom-global-fetch>
#[expect(non_snake_case)]
pub(crate) fn Fetch(
    global: &GlobalScope,
    input: RequestInfo,
    init: &RequestInit,
    cx: &mut CurrentRealm,
) -> RootedPromise {
    // Step 1. Let p be a new promise.
    let promise = Promise::new_in_realm(cx);

    // Step 7. Let responseObject be null.
    // NOTE: We do initialize the object earlier so we can use it to track errors.
    let response = Response::new_fetch_response(cx, global);
    response.Headers(cx).set_guard(Guard::Immutable);

    // Step 2. Let requestObject be the result of invoking the initial value of Request as constructor
    //         with input and init as arguments. If this throws an exception, reject p with it and return p.
    rooted!(&in(cx) let mut fetch_call_state = FetchCallState {
        promise: promise.to_traced(),
        response: response.as_traced(),
        locally_aborted: Cell::new(false),
    });
    let request_object =
        match Request::constructor(cx, global, None, input, init, Some(&fetch_call_state)) {
            Err(error) => {
                response.error_stream(cx, error.clone());
                promise.reject_error(cx, error);
                return promise;
            },
            Ok(request) => request,
        };
    // Step 3. Let request be requestObject’s request.
    let request = request_object.request().clone();
    let request_id = request.id;

    // Step 4. If requestObject’s signal is aborted, then:
    let signal = request_object.Signal();
    if signal.aborted() {
        // Step 4.1. Abort the fetch() call with p, request, null, and requestObject’s signal’s abort reason.
        rooted!(&in(cx) let mut abort_reason = UndefinedValue());
        signal.Reason(abort_reason.handle_mut());
        abort_fetch_call(
            &promise,
            &request_object,
            None,
            abort_reason.handle(),
            global,
            cx,
        );
        // Step 4.2. Return p.
        return promise;
    }

    // Step 5. Let globalObject be request’s client’s global object.
    // NOTE:   We already get the global object as an argument
    let mut request_builder = request_init_from_request(request, global);

    // Step 6. If globalObject is a ServiceWorkerGlobalScope object, then set request’s
    //         service-workers mode to "none".
    if global.is::<ServiceWorkerGlobalScope>() {
        request_builder.service_workers_mode = ServiceWorkersMode::None;
    }

    // Step 8. Let relevantRealm be this’s relevant realm.
    //
    // Is `comp` as argument

    // Step 9. Let locallyAborted be false.
    // Step 10. Let controller be null.
    let fetch_context = FetchContext {
        request_id,
        url: request_builder.url.url(),
    };
    let network_listener = NetworkListener::new(
        fetch_context,
        global.task_manager().networking_task_source().to_sendable(),
    );

    // Step 11. Add the following abort steps to requestObject’s signal:
    signal.add(&AbortAlgorithm::Fetch(request_object.as_traced()));

    // Step 12. Set controller to the result of calling fetch given request and
    // processResponse given response being these steps:
    global
        .fetch_group_mut()
        .fetch(request_builder, network_listener, Some(&request_object));

    // Step 13. Return p.
    promise
}

/// <https://fetch.spec.whatwg.org/#queue-a-deferred-fetch>
fn queue_deferred_fetch(
    request: NetTraitsRequest,
    activate_after: Finite<f64>,
    global: &GlobalScope,
) -> DeferredFetchRecordId {
    let trusted_global = Trusted::new(global);
    let mut request = request;
    // Step 1. Populate request from client given request.
    request.client = Some(global.request_client(None));
    request.populate_request_from_client();
    // Step 2. Set request’s service-workers mode to "none".
    request.service_workers_mode = ServiceWorkersMode::None;
    // Step 3. Set request’s keepalive to true.
    request.keep_alive = true;
    // Step 4. Let deferredRecord be a new deferred fetch record whose request is request, and whose notify invoked is onActivatedWithoutTermination.
    let deferred_record = DeferredFetchRecord {
        request,
        invoke_state: Cell::new(DeferredFetchRecordInvokeState::Pending),
        activated: Cell::new(false),
    };

    // Step 5. Append deferredRecord to request’s client’s fetch group’s deferred fetch records.
    let deferred_fetch_record_id = global
        .fetch_group_mut()
        .append_deferred_fetch(deferred_record);

    // Step 6. If activateAfter is non-null, then run the following steps in parallel:
    global.schedule_timer(TimerEventRequest {
        callback: Box::new(move || {
            // Step 6.2. Process deferredRecord.
            let global = trusted_global.root();
            let mut fetch_group = global.fetch_group_mut();
            let deferred_fetch_record =
                fetch_group.deferred_fetch_record_for_id(&deferred_fetch_record_id);
            fetch_group.process_a_deferred_fetch(&global, &deferred_fetch_record);

            // Last step of https://fetch.spec.whatwg.org/#process-a-deferred-fetch
            //
            // Step 4. Queue a global task on the deferred fetch task source with
            // deferredRecord’s request’s client’s global object to run deferredRecord’s notify invoked.
            let trusted_global = trusted_global.clone();
            global.task_manager().deferred_fetch_task_source().queue(
                task!(notify_deferred_record: move || {
                    trusted_global.root().fetch_group().deferred_fetch_record_for_id(&deferred_fetch_record_id).activate();
                }),
            );
        }),
        // Step 6.1. The user agent should wait until any of the following conditions is met:
        duration: Duration::from_millis(*activate_after as u64),
    });
    // Step 7. Return deferredRecord.
    deferred_fetch_record_id
}

/// <https://fetch.spec.whatwg.org/#dom-window-fetchlater>
#[expect(non_snake_case)]
pub(crate) fn FetchLater(
    cx: &mut JSContext,
    window: &Window,
    input: RequestInfo,
    init: &DeferredRequestInit,
) -> Fallible<DomRoot<FetchLaterResult>> {
    let global_scope = window.upcast();
    let document = window.Document();
    // Step 1. Let requestObject be the result of invoking the initial value
    // of Request as constructor with input and init as arguments.
    let request_object = Request::constructor(
        cx,
        global_scope,
        None,
        input,
        &init.parent,
        None, /* state */
    )?;
    // Step 2. If requestObject’s signal is aborted, then throw signal’s abort reason.
    let signal = request_object.Signal();
    if signal.aborted() {
        rooted!(&in(cx) let mut abort_reason = UndefinedValue());
        signal.Reason(abort_reason.handle_mut());
        assert!(!JS_IsExceptionPending(cx));
        JS_SetPendingException(cx, abort_reason.handle(), ExceptionStackBehavior::Capture);
        return Err(Error::JSFailed);
    }
    // Step 3. Let request be requestObject’s request.
    let request = request_object.request();
    // Step 4. Let activateAfter be null.
    let mut activate_after = Finite::wrap(0_f64);
    // Step 5. If init is given and init["activateAfter"] exists, then set
    // activateAfter to init["activateAfter"].
    if let Some(init_activate_after) = init.activateAfter.as_ref() {
        activate_after = *init_activate_after;
    }
    // Step 6. If activateAfter is less than 0, then throw a RangeError.
    if *activate_after < 0.0 {
        return Err(Error::Range(c"activateAfter must be at least 0".to_owned()));
    }
    // Step 7. If this’s relevant global object’s associated document is not fully active, then throw a TypeError.
    if !document.is_fully_active() {
        return Err(Error::Type(c"Document is not fully active".to_owned()));
    }
    let url = request.url();
    // Step 8. If request’s URL’s scheme is not an HTTP(S) scheme, then throw a TypeError.
    if !matches!(url.scheme(), "http" | "https") {
        return Err(Error::Type(c"URL is not http(s)".to_owned()));
    }
    // Step 9. If request’s URL is not a potentially trustworthy URL, then throw a SecurityError.
    if !url.is_potentially_trustworthy() {
        return Err(Error::Type(c"URL is not trustworthy".to_owned()));
    }
    // Step 10. If request’s body is not null, and request’s body length is null, then throw a TypeError.
    if request
        .body
        .as_ref()
        .is_some_and(|body| body.len().is_none())
    {
        return Err(Error::Type(c"Body is empty".to_owned()));
    }
    // Step 11. If the available deferred-fetch quota given request’s client and request’s URL’s
    // origin is less than request’s total request length, then throw a "QuotaExceededError" DOMException.
    let quota = document.available_deferred_fetch_quota(request.url().origin());
    let requested = request.total_request_length() as isize;
    if quota < requested {
        return Err(Error::QuotaExceeded {
            quota: Some(Finite::wrap(quota as f64)),
            requested: Some(Finite::wrap(requested as f64)),
        });
    }
    // Step 12. Let activated be false.
    // Step 13. Let deferredRecord be the result of calling queue a deferred fetch given request,
    // activateAfter, and the following step: set activated to true.
    let deferred_record_id = queue_deferred_fetch(request.clone(), activate_after, global_scope);
    // Step 14. Add the following abort steps to requestObject’s signal: Set deferredRecord’s invoke state to "aborted".
    signal.add(&AbortAlgorithm::FetchLater(deferred_record_id));
    // Step 15. Return a new FetchLaterResult whose activated getter steps are to return activated.
    Ok(FetchLaterResult::new(cx, window, deferred_record_id))
}

/// <https://fetch.spec.whatwg.org/#deferred-fetch-record-invoke-state>
#[derive(Clone, Copy, MallocSizeOf, PartialEq)]
pub(crate) enum DeferredFetchRecordInvokeState {
    Pending,
    Sent,
    Aborted,
}

/// <https://fetch.spec.whatwg.org/#deferred-fetch-record>
#[derive(MallocSizeOf)]
pub(crate) struct DeferredFetchRecord {
    /// <https://fetch.spec.whatwg.org/#deferred-fetch-record-request>
    pub(crate) request: NetTraitsRequest,
    /// <https://fetch.spec.whatwg.org/#deferred-fetch-record-invoke-state>
    pub(crate) invoke_state: Cell<DeferredFetchRecordInvokeState>,
    activated: Cell<bool>,
}

impl DeferredFetchRecord {
    /// Part of step 13 of <https://fetch.spec.whatwg.org/#dom-window-fetchlater>
    fn activate(&self) {
        // and the following step: set activated to true.
        self.activated.set(true);
    }
    /// Part of step 14 of <https://fetch.spec.whatwg.org/#dom-window-fetchlater>
    pub(crate) fn abort(&self) {
        // Set deferredRecord’s invoke state to "aborted".
        self.invoke_state
            .set(DeferredFetchRecordInvokeState::Aborted);
    }
    /// Part of step 15 of <https://fetch.spec.whatwg.org/#dom-window-fetchlater>
    pub(crate) fn activated_getter_steps(&self) -> bool {
        // whose activated getter steps are to return activated.
        self.activated.get()
    }
}

/// The captured state that is kept during a fetch operation.
#[derive(Clone, JSTraceable, MallocSizeOf)]
#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
pub(crate) struct FetchCallState {
    pub promise: TracedPromise,
    pub response: Dom<Response>,
    pub locally_aborted: Cell<bool>,
}

impl Rootable for FetchCallState {}

impl FetchCallState {
    /// Step 11 of <https://fetch.spec.whatwg.org/#dom-global-fetch>
    pub(crate) fn abort_fetch(
        &self,
        cx: &mut JSContext,
        request: &Request,
        abort_reason: HandleValue,
        global: &GlobalScope,
    ) {
        // Step 11.1. Set locallyAborted to true.
        self.locally_aborted.set(true);

        // Step 11.2. Assert: controller is non-null.
        //
        // Note: We currently prune fetch records that have finished (behaviorally
        // equivalent to the specification and better for memory usage), so it might be
        // the case that the `FetchRecord` is gone and the controller inaccessible.

        // Step 11.3. Abort controller with requestObject’s signal’s abort reason.
        if let Some(controller) = global
            .fetch_group_mut()
            .fetch_controller(&request.request().id)
        {
            controller.abort();
        }

        // Step 11.4. Abort the fetch() call with p, request, responseObject,
        // and requestObject’s signal’s abort reason.
        let promise = self.promise.root(cx);
        abort_fetch_call(
            &promise,
            request,
            Some(&self.response),
            abort_reason,
            global,
            cx,
        );
    }

    pub(crate) fn process_response(
        &self,
        cx: &mut JSContext,
        fetch_metadata: Result<FetchMetadata, NetworkError>,
    ) {
        // Step 12.1. If locallyAborted is true, then abort these steps.
        if self.locally_aborted.get() {
            return;
        }
        let mut realm = enter_auto_realm(cx, &*self.promise);
        let cx = &mut realm.current_realm();
        match fetch_metadata {
            // Step 12.3. If response is a network error, then reject
            // p with a TypeError and abort these steps.
            Err(error) => {
                self.promise
                    .reject_error(cx, Error::Type(cformat!("Network error: {:?}", error)));
                self.response.set_type(cx, DOMResponseType::Error);
                self.response
                    .error_stream(cx, Error::Type(c"Network error occurred".to_owned()));
                return;
            },
            // Step 12.4. Set responseObject to the result of creating a Response object,
            // given response, "immutable", and relevantRealm.
            Ok(metadata) => match metadata {
                FetchMetadata::Unfiltered(m) => {
                    fill_headers_with_metadata(cx, &self.response, m);
                    self.response.set_type(cx, DOMResponseType::Default);
                },
                FetchMetadata::Filtered { filtered, .. } => match filtered {
                    FilteredMetadata::Basic(m) => {
                        fill_headers_with_metadata(cx, &self.response, m);
                        self.response.set_type(cx, DOMResponseType::Basic);
                    },
                    FilteredMetadata::Cors(m) => {
                        fill_headers_with_metadata(cx, &self.response, m);
                        self.response.set_type(cx, DOMResponseType::Cors);
                    },
                    FilteredMetadata::Opaque => {
                        self.response.set_type(cx, DOMResponseType::Opaque);
                    },
                    FilteredMetadata::OpaqueRedirect(url) => {
                        self.response.set_type(cx, DOMResponseType::Opaqueredirect);
                        self.response.set_final_url(url);
                    },
                },
            },
        }

        // Step 12.5. Resolve p with responseObject.
        self.promise.resolve_native(cx, &*self.response);
    }

    pub(crate) fn process_response_chunk(&self, cx: &mut JSContext, chunk: Bytes) {
        self.response.stream_chunk(cx, chunk);
    }

    pub(crate) fn process_response_eof(
        &self,
        cx: &mut JSContext,
        response: &Result<(), NetworkError>,
    ) {
        let mut realm = enter_auto_realm(cx, &*self.response);
        let cx = &mut realm.current_realm();
        if let Err(NetworkError::DecompressionError) = response {
            self.response
                .error_stream(cx, Error::Type(c"Network error occurred".to_owned()));
        }
        self.response.finish(cx);
        // TODO
        // ... trailerObject is not supported in Servo yet.
    }
}

#[derive(JSTraceable, MallocSizeOf)]
pub(crate) struct FetchContext {
    #[no_trace]
    request_id: RequestId,
    #[no_trace]
    url: ServoUrl,
}

/// Step 12 of <https://fetch.spec.whatwg.org/#dom-global-fetch>
impl FetchResponseListener for FetchContext {
    fn process_request_body(&mut self, _: &GlobalScope, _: RequestId) {
        // TODO
    }

    fn process_response(
        &mut self,
        cx: &mut JSContext,
        global: &GlobalScope,
        request_id: RequestId,
        fetch_metadata: Result<FetchMetadata, NetworkError>,
    ) {
        let Some(request) = global.fetch_group().fetch_call_request(&request_id) else {
            return;
        };
        request.process_response(cx, fetch_metadata);
    }

    fn process_response_chunk(
        &mut self,
        cx: &mut JSContext,
        global: &GlobalScope,
        request_id: RequestId,
        chunk: Bytes,
    ) {
        let Some(call_state) = global.fetch_group().fetch_call_request(&request_id) else {
            return;
        };
        call_state.process_response_chunk(cx, chunk);
    }

    fn process_response_eof(
        self,
        cx: &mut JSContext,
        global: &GlobalScope,
        request_id: RequestId,
        response: Result<(), NetworkError>,
        timing: ResourceFetchTiming,
    ) {
        let call_state = global.fetch_group().fetch_call_request(&request_id);
        if let Some(call_state) = call_state {
            call_state.process_response_eof(cx, &response);
        };

        // navigation submission is handled in servoparser/mod.rs
        network_listener::submit_timing(cx, global, &self, &response, &timing);
    }

    fn process_csp_violations(
        &mut self,
        cx: &mut JSContext,
        global: &GlobalScope,
        _request_id: RequestId,
        violations: Vec<Violation>,
    ) {
        global.report_csp_violations(cx, violations, None, None);
    }
}

impl ResourceTimingListener for FetchContext {
    fn resource_timing_information(&self) -> (InitiatorType, ServoUrl) {
        (InitiatorType::Fetch, self.url.clone())
    }
}

struct FetchLaterListener {
    /// URL of this request.
    url: ServoUrl,
}

impl FetchResponseListener for FetchLaterListener {
    fn process_request_body(&mut self, _: &GlobalScope, _: RequestId) {}

    fn process_response(
        &mut self,
        _: &mut JSContext,
        _: &GlobalScope,
        _: RequestId,
        fetch_metadata: Result<FetchMetadata, NetworkError>,
    ) {
        _ = fetch_metadata;
    }

    fn process_response_chunk(
        &mut self,
        _: &mut JSContext,
        _: &GlobalScope,
        _: RequestId,
        chunk: Bytes,
    ) {
        _ = chunk;
    }

    fn process_response_eof(
        self,
        cx: &mut JSContext,
        global: &GlobalScope,
        _: RequestId,
        response: Result<(), NetworkError>,
        timing: ResourceFetchTiming,
    ) {
        network_listener::submit_timing(cx, global, &self, &response, &timing);
    }

    fn process_csp_violations(
        &mut self,
        cx: &mut JSContext,
        global: &GlobalScope,
        _request_id: RequestId,
        violations: Vec<Violation>,
    ) {
        global.report_csp_violations(cx, violations, None, None);
    }
}

impl ResourceTimingListener for FetchLaterListener {
    fn resource_timing_information(&self) -> (InitiatorType, ServoUrl) {
        (InitiatorType::Fetch, self.url.clone())
    }
}

fn fill_headers_with_metadata(cx: &mut JSContext, r: &Response, m: Metadata) {
    r.set_headers(cx, m.headers);
    r.set_status(&m.status);
    r.set_final_url(m.final_url);
    r.set_redirected(m.redirected);
}

pub(crate) trait CspViolationsProcessor {
    fn process_csp_violations(&self, cx: &mut JSContext, violations: Vec<Violation>);
}

/// Convenience function for synchronously loading a whole resource.
pub(crate) fn load_whole_resource(
    request: RequestBuilder,
    core_resource_thread: &CoreResourceThread,
    global: &GlobalScope,
    csp_violations_processor: &dyn CspViolationsProcessor,
    cx: &mut JSContext,
) -> Result<(Metadata, Vec<u8>, bool), NetworkError> {
    let (action_sender, action_receiver) = GenericCallback::new_blocking().unwrap();
    let url = request.url.url();
    core_resource_thread
        .send(CoreResourceMsg::Fetch(
            request,
            FetchChannels::ResponseMsg(action_sender),
        ))
        .unwrap();

    let mut buf = vec![];
    let mut metadata = None;
    let mut muted_errors = false;
    loop {
        match action_receiver.recv().unwrap() {
            FetchResponseMsg::ProcessRequestBody(..) => {},
            FetchResponseMsg::ProcessResponse(_, Ok(m)) => {
                muted_errors = m.is_cors_cross_origin();
                metadata = Some(match m {
                    FetchMetadata::Unfiltered(m) => m,
                    FetchMetadata::Filtered { unsafe_, .. } => unsafe_,
                })
            },
            FetchResponseMsg::ProcessResponseChunk(_, data) => buf.extend_from_slice(&data),
            FetchResponseMsg::ProcessResponseEOF(_, Ok(_), _) => {
                let metadata = metadata.unwrap();
                if let Some(timing) = &metadata.timing {
                    submit_timing_data(cx, global, url, InitiatorType::Other, timing);
                }
                return Ok((metadata, buf, muted_errors));
            },
            FetchResponseMsg::ProcessResponse(_, Err(e)) |
            FetchResponseMsg::ProcessResponseEOF(_, Err(e), _) => return Err(e),
            FetchResponseMsg::ProcessCspViolations(_, violations) => {
                csp_violations_processor.process_csp_violations(cx, violations);
            },
            FetchResponseMsg::ProcessContentLength(_request_id, size) => {
                buf.reserve(size.saturating_sub(buf.len()))
            },
        }
    }
}

pub(crate) trait RequestWithGlobalScope {
    fn with_global_scope(self, global: &GlobalScope) -> Self;
}

impl RequestWithGlobalScope for RequestBuilder {
    fn with_global_scope(self, global: &GlobalScope) -> Self {
        self.client(global.request_client(None))
            .pipeline_id(Some(global.pipeline_id()))
    }
}

/// <https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request>
/// This function is temporary, since it does not ensure that blob URLs are claimed
/// appropriately. All callers must migrate to create_a_potential_cors_request_with_claim.
#[allow(clippy::too_many_arguments)]
pub(crate) fn create_a_potential_cors_request(
    webview_id: Option<WebViewId>,
    url: ServoUrl,
    destination: Destination,
    cors_setting: Option<CorsSettings>,
    same_origin_fallback: Option<bool>,
    referrer: Referrer,
) -> RequestBuilder {
    create_a_potential_cors_request_with_claim(
        webview_id,
        UrlWithBlobClaim::from_url_without_having_claimed_blob(url),
        destination,
        cors_setting,
        same_origin_fallback,
        referrer,
    )
}

/// <https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request>
#[allow(clippy::too_many_arguments)]
pub(crate) fn create_a_potential_cors_request_with_claim(
    webview_id: Option<WebViewId>,
    url: UrlWithBlobClaim,
    destination: Destination,
    cors_setting: Option<CorsSettings>,
    same_origin_fallback: Option<bool>,
    referrer: Referrer,
) -> RequestBuilder {
    RequestBuilder::new(webview_id, url, referrer)
        // Step 1. Let mode be "no-cors" if corsAttributeState is No CORS, and "cors" otherwise.
        .mode(match cors_setting {
            Some(_) => RequestMode::CorsMode,
            // Step 2. If same-origin fallback flag is set and mode is "no-cors", set mode to "same-origin".
            None if same_origin_fallback == Some(true) => RequestMode::SameOrigin,
            None => RequestMode::NoCors,
        })
        .credentials_mode(match cors_setting {
            // Step 4. If corsAttributeState is Anonymous, set credentialsMode to "same-origin".
            Some(CorsSettings::Anonymous) => CredentialsMode::CredentialsSameOrigin,
            // Step 3. Let credentialsMode be "include".
            _ => CredentialsMode::Include,
        })
        // Step 5. Return a new request whose URL is url, destination is destination,
        // mode is mode, credentials mode is credentialsMode, and whose use-URL-credentials flag is set.
        .destination(destination)
        .use_url_credentials(true)
}