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Devtools: send error replies instead of ignoring messages (#37686)

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Client messages, which are always requests, are dispatched to Actor
instances one at a time via Actor::handle_message. Each request must be
paired with exactly one reply from the same actor the request was sent
to, where a reply is a message with no type (if a message from the
server has a type, it’s a notification, not a reply).

Failing to reply to a request will almost always permanently break that
actor, because either the client gets stuck waiting for a reply, or the
client receives the reply for a subsequent request as if it was the
reply for the current request. If an actor fails to reply to a request,
we want the dispatcher (ActorRegistry::handle_message) to send an error
of type `unrecognizedPacketType`, to keep the conversation for that
actor in sync. Since replies come in all shapes and sizes, we want to
allow Actor types to send replies without having to return them to the
dispatcher.

This patch adds a wrapper type around a client stream that guarantees
request/reply invariants. It allows the dispatcher to check if a valid
reply was sent, and guarantees that if the actor tries to send a reply,
it’s actually a valid reply (see ClientRequest::is_valid_reply). It does
not currently guarantee anything about messages sent via the TcpStream
released via ClientRequest::try_clone_stream or the return value of
ClientRequest::reply. We also send `unrecognizedPacketType`,
`missingParameter`, `badParameterType`, and `noSuchActor` messages per
the
[protocol](https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#error-packets)
[docs](https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#packets).

Testing: automated tests all pass, and manual testing looks ok
Fixes: #37683 and at least six bugs, plus one with a different root
cause, plus three with zero impact

---------

Signed-off-by: atbrakhi <atbrakhi@igalia.com>
Signed-off-by: Delan Azabani <dazabani@igalia.com>
Co-authored-by: delan azabani <dazabani@igalia.com>
Co-authored-by: Simon Wülker <simon.wuelker@arcor.de>
Co-authored-by: the6p4c <me@doggirl.gay>
This commit is contained in:
atbrakhi 2025-07-07 14:40:44 +02:00 • committed by GitHub
parent fcb2a4cd95
commit 71d97bd935
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36 changed files with 661 additions and 637 deletions
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62
components/devtools/actor.rs
View file

@ -12,14 +12,37 @@ use std::sync::{Arc, Mutex};
use base::cross_process_instant::CrossProcessInstant;
use base::id::PipelineId;
use log::debug;
use serde_json::{Map, Value};
use serde_json::{Map, Value, json};
use crate::StreamId;
use crate::protocol::{ClientRequest, JsonPacketStream};
#[derive(PartialEq)]
pub enum ActorMessageStatus {
Processed,
Ignored,
/// Error replies.
///
/// <https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#error-packets>
#[derive(Debug)]
pub enum ActorError {
MissingParameter,
BadParameterType,
UnrecognizedPacketType,
/// Custom errors, not defined in the protocol docs.
/// This includes send errors, and errors that prevent Servo from sending a reply.
Internal,
}
impl ActorError {
pub fn name(&self) -> &'static str {
match self {
ActorError::MissingParameter => "missingParameter",
ActorError::BadParameterType => "badParameterType",
ActorError::UnrecognizedPacketType => "unrecognizedPacketType",
// The devtools frontend always checks for specific protocol errors by catching a JS exception `e` whose
// message contains the error name, and checking `e.message.includes("someErrorName")`. As a result, the
// only error name we can safely use for custom errors is the empty string, because any other error name we
// use may be a substring of some upstream error name.
ActorError::Internal => "",
}
}
}
/// A common trait for all devtools actors that encompasses an immutable name
@ -28,12 +51,12 @@ pub enum ActorMessageStatus {
pub(crate) trait Actor: Any + ActorAsAny {
fn handle_message(
&self,
request: ClientRequest,
registry: &ActorRegistry,
msg_type: &str,
msg: &Map<String, Value>,
stream: &mut TcpStream,
stream_id: StreamId,
) -> Result<ActorMessageStatus, ()>;
) -> Result<(), ActorError>;
fn name(&self) -> String;
fn cleanup(&self, _id: StreamId) {}
}
@ -169,8 +192,8 @@ impl ActorRegistry {
actor.actor_as_any_mut().downcast_mut::<T>().unwrap()
}
/// Attempt to process a message as directed by its `to` property. If the actor is not
/// found or does not indicate that it knew how to process the message, ignore the failure.
/// Attempt to process a message as directed by its `to` property. If the actor is not found, does not support the
/// message, or failed to handle the message, send an error reply instead.
pub(crate) fn handle_message(
&mut self,
msg: &Map<String, Value>,
@ -186,17 +209,20 @@ impl ActorRegistry {
};
match self.actors.get(to) {
None => log::warn!("message received for unknown actor \"{}\"", to),
None => {
// <https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#packets>
let msg = json!({ "from": to, "error": "noSuchActor" });
let _ = stream.write_json_packet(&msg);
},
Some(actor) => {
let msg_type = msg.get("type").unwrap().as_str().unwrap();
if actor.handle_message(self, msg_type, msg, stream, stream_id)? !=
ActorMessageStatus::Processed
{
log::warn!(
"unexpected message type \"{}\" found for actor \"{}\"",
msg_type,
to
);
if let Err(error) = ClientRequest::handle(stream, to, |req| {
actor.handle_message(req, self, msg_type, msg, stream_id)
}) {
// <https://firefox-source-docs.mozilla.org/devtools/backend/protocol.html#error-packets>
let _ = stream.write_json_packet(&json!({
"from": actor.name(), "error": error.name()
}));
}
},
}