HTTP server may not read chunked encoding response body again

[nwtgck]

Zig Version

0.11.0-dev.2682+d80e6ca5a

Steps to Reproduce and Observed Behavior

Here is server.zig.

const std = @import("std");

pub fn main() !void {
    const max_header_size = 8192;
    var server = std.http.Server.init(std.heap.page_allocator, .{ .reuse_address = true });
    defer server.deinit();

    const address = try std.net.Address.parseIp("0.0.0.0", 8080);
    std.debug.print("Listening on {} ...\n", .{address});
    try server.listen(address);

    while (true) {
        const res = try server.accept(.{ .dynamic = max_header_size });
        const thread = try std.Thread.spawn(.{}, handler, .{res});
        thread.detach();
    }
}

fn handler(res: *std.http.Server.Response) !void {
    defer res.reset();

    try res.wait();
    const finish_body: []const u8 = "Sent your data!\n";
    res.transfer_encoding = .{ .content_length = finish_body.len };
    try res.headers.append("Connection", "close");
    try res.do();

    var buf: [16]u8 = .{};
    var n: u64 = 1;
    while (true) {
        const size = try res.read(&buf);
        if (size == 0) {
            break;
        }
        std.debug.print("{}) size={}, buf={any}\n", .{ n, size, buf[0..size] });
        n += 1;
    }
    _ = try res.write(finish_body);
    try res.finish();
}

Run zig run server.zig and request with curl as follows and then I had an error.

$ echo ABC | curl -sST- localhost:8080/mypath
curl: (18) transfer closed with 16 bytes remaining to read

Here is the server log.

$ zig run server.zig 
Listening on 0.0.0.0:8080 ...
1) size=4, buf={ 65, 66, 67, 10 }
!!!! state:http.protocol.State.seen_rn
!!!! has_trail:true
error: InvalidTrailers
/Users/ryo/ws/zig/zig/build/stage3/lib/zig/std/http/Server.zig:266:60: 0x102d68d97 in parse (server)
                        if (req.transfer_encoding != null) return error.HttpHeadersInvalid;
                                                           ^
/Users/ryo/ws/zig/zig/build/stage3/lib/zig/std/http/Server.zig:537:80: 0x102d3271f in read (server)
                res.request.parse(res.request.parser.header_bytes.items) catch return error.InvalidTrailers;
                                                                               ^
/Users/ryo/ws/zig/piping-server-zig/server.zig:31:22: 0x102d3138b in handler (server)
        const size = try res.read(&buf);
                     ^

The comments begining with !!!! were added by me like the follwing positions:

A request with fixed length body works as follows.

$ curl -sS --data-binary ABCD localhost:8080/mypath
Sent your data!

Expected Behavior

$ echo ABC | curl -isST- localhost:8080/mypath                                                                          
Sent your data!      

Reference

Trailer example in MDN

HTTP/1.1 200 OK
Content-Type: text/plain
Transfer-Encoding: chunked
Trailer: Expires

7\r\n
Mozilla\r\n
9\r\n
Developer\r\n
7\r\n
Network\r\n
0\r\n
Expires: Wed, 21 Oct 2015 07:28:00 GMT\r\n
\r\n

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Trailer

[nwtgck]

@truemedian Thank you for implementing HTTP server!
Unfortunately, I had a different chunked encoding error after #15299 ...

[truemedian]

Do you have code that can reproduce the new error?

[nwtgck]

Sorry for confusion. The code in the first comment in the PR is the code and the new error.