bazel: make coverage great again (#415). (#781)

* Get rid of custom Bazel build. Now that we have a single test binary,
  we can completely bypass "bazel coverage", instead doing an
  unsandboxed "build test" with --coverage added to --cxxopt/--linkopt.
  We then have the .gcda from the single run in bazel-out/ and can run
  gcovr on it.

* Document how to do coverage runs locally (i.e. not in the CI Docker
  image).

bazel/README.md

@@ -115,6 +115,18 @@ One caveat to note is that the Git SHA1 is truncated to 16 bytes today as a
 result of the workaround in place for
 https://github.com/bazelbuild/bazel/issues/2805.
 
+# Coverage builds
+
+To generate coverage results, make sure you have `gcov` 3.3 in your `PATH` (or
+set `GCOVR` to point at it). Then run:
+
+```
+test/run_envoy_bazel_coverage.sh
+```
+
+The summary results are printed to the standard output and the full coverage
+report is available in `generated/coverage/coverage.html`.
+
 # Adding or maintaining Envoy build rules
 
 See the [developer guide for writing Envoy Bazel rules](DEVELOPER.md).

ci/build_container/build_container.sh

@@ -20,17 +20,6 @@ apt-get update
 apt-get install -y bazel
 rm -rf /var/lib/apt/lists/*
 
-# Build a version of Bazel suitable for C++ code coverage collection. See
-# https://github.com/bazelbuild/bazel/issues/1118 for why we need this. This is the envoy-coverage
-# branch on the cloned repository.
-git clone https://github.com/htuch/bazel.git /tmp/bazel-coverage
-pushd /tmp/bazel-coverage
-git checkout 63f0542560773e973c9963845d5bbc30be75441a
-bazel build --spawn_strategy=standalone --genrule_strategy=standalone //src:bazel
-cp bazel-bin/src/bazel /usr/bin/bazel-coverage
-popd
-rm -rf /root/.cache /tmp/bazel-coverage
-
 # virtualenv
 pip install virtualenv
 

ci/build_setup.sh

@@ -44,7 +44,6 @@ then
   export USER=bazel
   export TEST_TMPDIR=/build/tmp
   export BAZEL="bazel"
-  export BAZEL_COVERAGE="bazel-coverage"
   # Not sandboxing, since non-privileged Docker can't do nested namespaces.
   BAZEL_OPTIONS="--package_path %workspace%:/source"
   export BAZEL_QUERY_OPTIONS="${BAZEL_OPTIONS}"

test/run_envoy_bazel_coverage.sh

@@ -4,28 +4,30 @@ set -e
 
 [[ -z "${SRCDIR}" ]] && SRCDIR="${PWD}"
 [[ -z "${REAL_SRCDIR}" ]] && REAL_SRCDIR="${SRCDIR}"
-[[ -z "${GCOVR_DIR}" ]] && GCOVR_DIR="${SRCDIR}/bazel-envoy"
+[[ -z "${GCOVR_DIR}" ]] && GCOVR_DIR="${SRCDIR}/bazel-$(basename "${SRCDIR}")"
 [[ -z "${TESTLOGS_DIR}" ]] && TESTLOGS_DIR="${SRCDIR}/bazel-testlogs"
 [[ -z "${BAZEL_COVERAGE}" ]] && BAZEL_COVERAGE=bazel
 [[ -z "${GCOVR}" ]] && GCOVR=gcovr
 
 # Make sure //test/coverage is up-to-date.
 (BAZEL_BIN="${BAZEL_COVERAGE}" "${REAL_SRCDIR}"/test/coverage/gen_build.sh)
 
-# Run all tests under bazel coverage.
-"${BAZEL_COVERAGE}" coverage //test/coverage:coverage_tests ${BAZEL_BUILD_OPTIONS} \
-  --cache_test_results=no --instrumentation_filter="" \
-  --test_output=all \
-  --coverage_support=@bazel_tools//tools/coverage:coverage_support
-
-# Cleanup any artifacts from previous coverage runs.
-rm -f $(find "${GCOVR_DIR}" -name "*.gcda" -o -name "*.gcov")
-
-# Unpack .gcda.gcno from coverage run. This needs to be done in the Envoy source directory with
-# bazel-out/ underneath it since gcov expects files to be available at their relative build
-# location. This can be done somewhere else, e.g. /tmp, but it involves complex copying or
-# symlinking of files to that location.
-(cd "${GCOVR_DIR}"; tar -xvf "${TESTLOGS_DIR}"/test/coverage/coverage_tests/coverage.dat)
+echo "Cleaning .gcda/.gcov from previous coverage runs..."
+for f in $(find -L "${GCOVR_DIR}" -name "*.gcda" -o -name "*.gcov")
+do
+  rm -f "${f}"
+done
+echo "Cleanup completed."
+
+# Run all tests under "bazel test", no sandbox. We're going to generate the
+# .gcda inplace in the bazel-out/ directory. This is in contrast to the "bazel
+# coverage" method, which is currently broken for C++ (see
+# https://github.com/bazelbuild/bazel/issues/1118). This works today as we have
+# a single coverage test binary and do not require the "bazel coverage" support
+# for collecting multiple traces and glueing them together.
+"${BAZEL_COVERAGE}" test //test/coverage:coverage_tests ${BAZEL_BUILD_OPTIONS} \
+  --cache_test_results=no --cxxopt="--coverage" --linkopt="--coverage" \
+  --test_output=all --strategy=Genrule=standalone --spawn_strategy=standalone
 
 # The Bazel build has a lot of whack in it, in particular generated files, headers from external
 # deps, etc. So, we exclude this from gcov to avoid false reporting of these files in the html and
@@ -41,6 +43,7 @@ COVERAGE_SUMMAY="${COVERAGE_DIR}/coverage_summary.txt"
 # gcovr is extremely picky about where it is run and where the paths of the
 # original source are relative to its execution location.
 cd "${SRCDIR}"
+echo "Running gcovr..."
 time "${GCOVR}" --gcov-exclude="${GCOVR_EXCLUDE_REGEX}" \
   --exclude-directories=".*/external/.*" --object-directory="${GCOVR_DIR}" -r "${SRCDIR}" \
   --html --html-details --exclude-unreachable-branches --print-summary \