refactor channel push and pop return values

[wokron]

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[Copilot]

Pull request overview

This PR refactors condy::Channel to use errno-style integer return codes for both synchronous (try_push/try_pop) and coroutine (push/pop) operations, and updates tests/docs accordingly while introducing a deprecated legacy channel API for the previous behavior.

Changes:

• Change Channel push/pop APIs to return int / (int, T) results (e.g., 0, -EAGAIN, -EPIPE, -ECANCELED) instead of bool/optional/exceptions.
• Update channel-related tests to match the new return types and error codes.
• Add condy::legacy::Channel (deprecated) and update guide/benchmark code for the new API.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
include/condy/channel.hpp	Refactors Channel API and awaiter completion to use errno-style results; includes legacy header.
include/condy/channel_legacy.hpp	Adds deprecated legacy channel implementation preserving prior semantics.
tests/test_channel.cpp	Updates channel unit tests to the new return conventions.
tests/test_async_operations.1.cpp	Adjusts channel pop usage in async recvmsg multishot test to new return type.
tests/test_async_operations.2.cpp	Adjusts channel push/pop usage in async read multishot tests to new return type.
tests/test_async_operations.3.cpp	Adjusts channel push/pop usage in async recv multishot tests to new return type.
docs/guide.md	Updates guide examples to new channel pop contract and closes channel in producer example.
benchmarks/channel.cpp	Updates benchmark consumer to destructure new pop return type.

Comments suppressed due to low confidence (1)

tests/test_channel.cpp:370

• This test still relies on item == 0 to detect a closed channel, but the refactor makes pop() return an explicit error code. Please check r == 0 for the first max_items pops, and then assert r == -EPIPE after push_close() (instead of relying on a default value) so the test matches the new API semantics.

    auto consumer = [&]() -> condy::Coro<void> {
        for (size_t i = 0; i < 2 * max_items; ++i) {
            auto [r, item] = co_await channel.pop();
            if (i < max_items) {
                REQUIRE(item == static_cast<int>(i + 1));
            } else {
                REQUIRE(item == 0); // Default indicates closed channel
            }
        }

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

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