kafka/error: define is_error_code_enum trait in error.h

[tchaikov]

move the is_error_code_enumkafka::error_code trait into error.h
where kafka::error_code is defined. this would help us ease the
pain of fight with the failures like:

FAILED: src/v/pandaproxy/CMakeFiles/v_pandaproxy_common.dir/server.cc.o
ccache /usr/bin/clang++-15 -DBOOST_ASIO_HAS_STD_INVOKE_RESULT -DFMT_LOCALE -DFMT_SHARED -DSEASTAR_API_LEVEL=6 -DSEASTAR_DEBUG -DSEASTAR_DEBUG_SHARED_PTR -DSEASTAR_DEFAULT_ALLOCATOR -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SHUFFLE_TASK_QUEUE -DSEASTAR_TYPE_ERASE_MORE -DXXH_PRIVATE_API -DZSTD_STATIC_LINKING_ONLY -I/home/kefu/dev/redpanda/src/v -I/home/kefu/dev/redpanda/build/src/v -isystem /home/kefu/dev/redpanda/build/deps_install/include -isystem /home/kefu/dev/redpanda/build/deps_install/include/hdr -fPIC -fsanitize=undefined -fsanitize=address -fcolor-diagnostics -g -fPIC -Wall -Wextra -Werror -Wno-missing-field-initializers -std=c++20 -U_FORTIFY_SOURCE -DSEASTAR_SSTRING -Werror=unused-result "-Wno-error=#warnings" -fstack-clash-protection -fsanitize=address -fsanitize=undefined -fno-sanitize=vptr -std=c++20 -MD -MT src/v/pandaproxy/CMakeFiles/v_pandaproxy_common.dir/server.cc.o -MF src/v/pandaproxy/CMakeFiles/v_pandaproxy_common.dir/server.cc.o.d -o src/v/pandaproxy/CMakeFiles/v_pandaproxy_common.dir/server.cc.o -c /home/kefu/dev/redpanda/src/v/pandaproxy/server.cc
In file included from /home/kefu/dev/redpanda/src/v/pandaproxy/server.cc:17:
In file included from /home/kefu/dev/redpanda/src/v/pandaproxy/reply.h:16:
/home/kefu/dev/redpanda/src/v/pandaproxy/error.h:73:8: error: explicit specialization of 'std::is_error_code_enum<kafka::error_code>' after instantiation
struct is_error_code_enum<kafka::error_code> : true_type {};
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/system_error:206:17: note: implicit instantiation first required here
             enable_if<is_error_code_enum<_ErrorCodeEnum>::value>::type>
                       ^
In file included from /home/kefu/dev/redpanda/src/v/pandaproxy/server.cc:17:
/home/kefu/dev/redpanda/src/v/pandaproxy/reply.h:103:16: error: no matching function for call to 'errored_body'
        return errored_body(e.error, e.what());
               ^~~~~~~~~~~~
/home/kefu/dev/redpanda/src/v/pandaproxy/reply.h:70:1: note: candidate function not viable: no known conversion from 'const kafka::error_code' to 'std::error_condition' for 1st argument
errored_body(std::error_condition ec, ss::sstring msg) {
^
/home/kefu/dev/redpanda/src/v/pandaproxy/reply.h:80:1: note: candidate function not viable: no known conversion from 'const kafka::error_code' to 'std::error_code' for 1st argument
errored_body(std::error_code ec, ss::sstring msg) {
^
2 errors generated.

Signed-off-by: Kefu Chai tchaikov@gmail.com

Cover letter

Describe in plain language the motivation (bug, feature, etc.) behind the change in this PR and how the included commits address it.

Fixes #ISSUE-NUMBER, Fixes #ISSUE-NUMBER, ...

Release notes

[tchaikov]

without this change, the tree just does not compile with clang-15. and i think it'd be a better practice to colocate the traits along with the "traited" type, hence the change.

[BenPope]

Thanks @tchaikov, I'm following along with the changes you're proposing, but have very limited time until early next month.

I think it makes sense to move make_error_code(error_code) too.

[tchaikov]

Thanks @tchaikov, I'm following along with the changes you're proposing, but have very limited time until early next month.

@BenPope hi Ben, sure. please take your time.

I think it makes sense to move make_error_code(error_code) too.

agreed! moved and repushed.

[BenPope]

There's a compilation failure:

../../../src/v/kafka/protocol/errors.cc:206:35: error: use of undeclared identifier 'pandaproxy'
--
  | return {static_cast<int>(ec), pandaproxy::kafka_error_category};

[BenPope]

There's a compilation failure:

../../../src/v/kafka/protocol/errors.cc:206:35: error: use of undeclared identifier 'pandaproxy'
--
  | return {static_cast<int>(ec), pandaproxy::kafka_error_category};

[BenPope]

@tchaikov Thanks for this. Unfortunately this creates a dependency cycle between kafka and pandaproxy, which already exists in the other direction.

I did some hacking and this is about the best I came up with: #4722

[tchaikov]

@tchaikov Thanks for this. Unfortunately this creates a dependency cycle between kafka and pandaproxy, which already exists in the other direction.

I did some hacking and this is about the best I came up with: #4722

@BenPope hi Ben, thanks for investigating into this, i meant to post my concern on this dependency. not only it introduces a cyclic dependency but also it is a bad smell -- i felt that kafka should be a relatively low-level facility which is supposed to be a dependency of other CMake targets like pandaproxy.

i will close my PR once yours gets approved and merged.