ABSL_FLAG macro triggers abseil-no-namespace check

[Alok Priyadarshi]

Describe the bug

ABSL_FLAG triggers clang-tidy abseil-no-namespace check

Steps to reproduce the bug

$ cat main.cc

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"

ABSL_FLAG(std::string, input, "input", "input file path");

int main(int argc, char* argv[]) {
  absl::ParseCommandLine(argc, argv);

  return EXIT_SUCCESS;
}

clang-tidy --checks=abseil-* main.cc

main.cc:7:1: error: namespace 'absl' is reserved for implementation of the Abseil library and should not be opened in user code [abseil-no-namespace,-warnings-as-errors]
ABSL_FLAG(std::string, input, "input", "input file path");
^
external/com_google_absl/absl/flags/flag.h:166:3: note: expanded from macro 'ABSL_FLAG'
  ABSL_FLAG_IMPL(Type, name, default_value, help)
  ^
external/com_google_absl/absl/flags/flag.h:269:13: note: expanded from macro 'ABSL_FLAG_IMPL'
  namespace absl /* block flags in namespaces */ {}                           \
            ^

What version of Abseil are you using?

f3489c9

What operating system and version are you using

Ubuntu 18.04

What compiler and version are you using?

clang-tidy-13

What build system are you using?

bazel 4.2.2

[Derek Mauro]

The Abseil library is working correctly in this case. ABSL_FLAG needs to be exempted from the clang-tidy check. I'll need to track down someone who can make the change to clang-tidy.

[Matt Armstrong]

This bug just got more interesting because with the new Abseil logging projects can reasonably attempt to switch from glog/gflags to the Abseil equivalents.

Workaround: put this, or something like it, in your project's .clang-tidy file:

Checks: 'abseil-*,-abseil-no-namespace'