Add default reporter for Bazel integration

[lukokr-aarch64]

bazel test sets the XML_OUTPUT_FILE environment variable which
specifies where the JUnit output of the test executable should be
written.

Picking up this variable allows catch2 to naturally integrate into
the Bazel testing ecosystem out-of-the-box.

This allows the user to simply depend on the catch2_main:

cc_test(
    name = "010-TestCase",
    srcs =["examples/010-TestCase.cpp"],
    copts = ["-std=c++14"],
    deps = [":catch2_main"],
)

And Bazel will pick up the test.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<testsuites>
  <testsuite name="010-TestCase" errors="0" failures="1" tests="5" hostname="tbd" time="0.000" timestamp="2022-03-23T08:48:13Z">
    <properties>
      <property name="random-seed" value="673971538"/>
    </properties>
    <testcase classname="010-TestCase.global" name="Factorial of 0 is 1 (fail)" time="0.000" status="run">
      <failure message="Factorial(0) == 1" type="REQUIRE">
FAILED:
  REQUIRE( Factorial(0) == 1 )
with expansion:
  0 == 1
at examples/010-TestCase.cpp:11
      </failure>
    </testcase>
    <testcase classname="010-TestCase.global" name="Factorials of 1 and higher are computed (pass)" time="0.000" status="run"/>
    <system-out/>
    <system-err/>
  </testsuite>
</testsuites>

But when running bazelisk test //... --test_output=all Bazel will show the user readable output:

INFO: From Testing //:010-TestCase:
==================== Test output for //:010-TestCase:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
010-TestCase is a Catch2 v3.0.0-preview.4 host application.
Run with -? for options

Randomness seeded to: 3971943524

-------------------------------------------------------------------------------
Factorial of 0 is 1 (fail)
-------------------------------------------------------------------------------
examples/010-TestCase.cpp:10
...............................................................................

examples/010-TestCase.cpp:11: FAILED:
  REQUIRE( Factorial(0) == 1 )
with expansion:
  0 == 1

===============================================================================
test cases: 2 | 1 passed | 1 failed
assertions: 5 | 4 passed | 1 failed

================================================================================

This was originally proposed in #2333 which was reworked with multi-reporter, added a test and fixed the bazel build.

I think from Bazel PoV it is preferable to keep XML_OUTPUT_FILE as a generic env variable that other frameworks recognise based on this TODO: https://github.com/bazelbuild/bazel/blob/1024358d1160a7eafb760300abd4533f160c33f2/tools/test/test-setup.sh#L108-L110

But if that's absolutely not acceptable I could try upstreaming BAZEL_XML_OUTPUT_FILE and change this PR, let me know what you think 😄

[codecov]

Codecov Report

Merging #2399 (7f99ee9) into devel (4b78157) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##            devel    #2399   +/-   ##
=======================================
  Coverage   91.11%   91.11%           
=======================================
  Files         155      155           
  Lines        7425     7425           
=======================================
  Hits         6765     6765           
  Misses        660      660           

[lukokr-aarch64]

Hi @horenmar, I picked this up from @mattyclarkson and his original PR #2333, I took your advice and used the work you did with multi-reporter. I would appreciate your review if you have a moment.
Cheers!

[horenmar]

I only spot-checked the changes to BUILD.bazel, otherwise this seems to be on the right track.

[Vertexwahn]

Please replace the WORKSPACE file with the following content:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "bazel_skylib",
    strip_prefix = "bazel-skylib-2a87d4a62af886fb320883aba102255aba87275e",
    urls = [
        "https://github.com/bazelbuild/bazel-skylib/archive/2a87d4a62af886fb320883aba102255aba87275e.tar.gz",
    ],
    sha256 = "d847b08d6702d2779e9eb399b54ff8920fa7521dc45e3e53572d1d8907767de7",
)

load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")

bazel_skylib_workspace()

Currently, bazel-skylib from https://github.com/Vertexwahn/bazel-skylib is used. Luckily, the changes I did to bazel-skylib are now part of the official bazel-skylib main branch

See also here: #2405

[lukokr-aarch64]

Thanks for the review, I will address your comments and push a new patchset

[lukokr-aarch64]

Hey thanks @horenmar for fixing the reporter spec, I was wresting with the default constructor on some of the builds.

[horenmar]

I am gonna let the Appveyor CI run and merge it when I have time afterwards -- I don't expect it to fail though.

Anyway, two more things

BAZEL_XML_OUTPUT_FILE

I would like to see it upstreamed, because with the prefixed name it doesn't have to be conditionally compiled. As it is, it is squatting on pretty valuable real estate in terms of env vars (squatting on valuable real estate seems to be a pattern with google c++ tho grumble grumble).

2. Please don't force push every change into single commit next time, it makes reviewing the review fixes hard, because I have to read the full thing again.

[lukokr-aarch64]

Agreed, on both points. Thanks again @horenmar. I'll raise a PR in Bazel regarding the env var.