thespian/test/remote_lifetime_test.zig

/// Tests cross-endpoint actor lifetime and exit propagation via the wire
/// "link" protocol.
///
/// Scenario (full round-trip):
///
///   1. Parent sends send_named to "die_test" (from_id=0, trigger mode).
///   2. Child die_test echoes payload back — proxy_4 is created on the parent,
///      message arrives FROM proxy_4 at TestActor.
///   3. TestActor sends {"link"} to proxy_4, establishing a Thespian link
///      between proxy_4 and TestActor AND requesting a wire "link" message.
///   4. Wire ["link", TA_wire_id, 4] reaches child; child's StdioEndpoint
///      calls actor.link() on die_test and records the mapping in link_notify.
///   5. TestActor sends {"die"} to proxy_4, which forwards it over the wire
///      to die_test (to_id=4).
///   6. die_test receives from_id != 0 and exits "die_test".
///   7. Child's StdioEndpoint receives the trapped exit from die_test, sends
///      wire ["exit", 4, "die_test"] to the parent.
///   8. Parent endpoint dispatches to proxy_4 via proxies[4], sends
///      {"exit", "die_test"} to proxy_4.
///   9. proxy_4 exits "die_test"; TestActor (Thespian-linked to proxy_4)
///      receives {"exit", "die_test"} and exits "success".
const std = @import("std");
const thespian = @import("thespian");
const cbor = @import("cbor");
const endpoint = @import("endpoint");
const build_options = @import("build_options");

var trace_file: ?std.fs.File = null;
var trace_buf: [4096]u8 = undefined;
var trace_file_writer: std.fs.File.Writer = undefined;

fn trace_handler(buf: thespian.message.c_buffer_type) callconv(.c) void {
    if (trace_file == null) return;
    cbor.toJsonWriter(buf.base[0..buf.len], &trace_file_writer.interface, .{}) catch return;
    trace_file_writer.interface.writeByte('\n') catch return;
}

const Allocator = std.mem.Allocator;
const result = thespian.result;
const pid_ref = thespian.pid_ref;
const Receiver = thespian.Receiver;
const message = thespian.message;

const TestActor = struct {
    allocator: Allocator,
    ep: thespian.pid,
    receiver: Receiver(*@This()),
    state: enum { waiting_for_trigger_reply, waiting_for_proxy_exit },

    const Args = struct { allocator: Allocator };

    fn start(args: Args) result {
        return init(args) catch |e| return thespian.exit_error(e, @errorReturnTrace());
    }

    fn init(args: Args) !void {
        // Trap exits so {"exit", reason} arrives as a message rather than
        // killing the actor; we need to inspect the exit reason.
        _ = thespian.set_trap(true);

        thespian.env.get().proc_set("test_receiver", thespian.self_pid().ref());

        const argv = try args.allocator.dupe(u8, message.fmt(.{build_options.remote_child_endpoint_path}).buf);
        const ep = try thespian.spawn_link(
            args.allocator,
            endpoint.Args{
                .allocator = args.allocator,
                .argv = argv,
            },
            endpoint.start,
            "endpoint",
        );

        // Trigger die_test in trigger mode (from_id=0): child echoes payload
        // back so the parent can establish proxy_4.
        try ep.send(.{ "send", @as(u64, 0), "die_test", .{"trigger"} });

        const self = try args.allocator.create(@This());
        self.* = .{
            .allocator = args.allocator,
            .ep = ep,
            .receiver = .init(receive_fn, deinit, self),
            .state = .waiting_for_trigger_reply,
        };
        errdefer self.deinit();
        thespian.receive(&self.receiver);
    }

    fn deinit(self: *@This()) void {
        self.ep.deinit();
        self.allocator.destroy(self);
    }

    fn receive_fn(self: *@This(), from: pid_ref, m: message) result {
        return self.receive(from, m) catch |e| return thespian.exit_error(e, @errorReturnTrace());
    }

    fn receive(self: *@This(), from: pid_ref, m: message) !void {
        var reason: []const u8 = "";
        switch (self.state) {
            .waiting_for_trigger_reply => {
                if (try m.match(.{"trigger"})) {
                    // `from` is proxy_4 (the proxy for die_test, remote_id=4).
                    //
                    // 1. Send {"link"} so proxy_4 establishes a Thespian link
                    //    with this actor AND sends the wire "link" message to
                    //    the child, which will monitor die_test.
                    try from.send(.{"link"});
                    //
                    // 2. Send {"die"} to proxy_4; it is forwarded over the wire
                    //    to die_test (to_id=4), causing it to exit "die_test".
                    //    Ordering is guaranteed: "link" is processed by the
                    //    child before the die trigger because both travel through
                    //    the same in-order pipe.
                    try from.send(.{"die"});
                    self.state = .waiting_for_proxy_exit;
                } else {
                    return thespian.unexpected(m);
                }
            },
            .waiting_for_proxy_exit => {
                if (try m.match(.{ "exit", thespian.extract(&reason) })) {
                    if (std.mem.eql(u8, reason, "die_test"))
                        return thespian.exit("success");
                    // Any other exit (e.g. endpoint crash) is a failure.
                    return thespian.unexpected(m);
                } else {
                    return thespian.unexpected(m);
                }
            },
        }
    }
};

test "remote: cross-process link/exit propagation via wire link protocol" {
    const allocator = std.testing.allocator;

    var initial_env: ?thespian.env = null;
    if (std.posix.getenv("TRACE") != null) {
        const f = try std.fs.cwd().createFile("remote_lifetime_trace.json", .{});
        trace_file = f;
        trace_file_writer = f.writer(&trace_buf);
        var e = thespian.env.init();
        e.on_trace(&trace_handler);
        e.enable_all_channels();
        initial_env = e;
    }
    defer if (initial_env) |e| {
        trace_file_writer.interface.flush() catch {};
        trace_file.?.close();
        trace_file = null;
        e.deinit();
    };

    var ctx = try thespian.context.init(allocator);
    defer ctx.deinit();

    var success = false;
    var exit_handler = thespian.make_exit_handler(&success, struct {
        fn handle(ok: *bool, status: []const u8) void {
            ok.* = std.mem.eql(u8, status, "success");
        }
    }.handle);

    _ = try ctx.spawn_link(
        TestActor.Args{ .allocator = allocator },
        TestActor.start,
        "test_actor",
        &exit_handler,
        if (initial_env) |*e| e else null,
    );

    ctx.run();

    if (!success) return error.TestFailed;
}