create a script for automating code coverage

.config/nextest.toml

@@ -4,3 +4,10 @@ status-level = "all"
 final-status-level = "skip"
 failure-output = "immediate-final"
 fail-fast = false
+
+[profile.coverage]
+retries = 0
+status-level = "all"
+final-status-level = "skip"
+failure-output = "immediate-final"
+fail-fast = false

.gitignore

@@ -1,6 +1,7 @@
 # spell-checker:ignore (misc) direnv
 
 target/
+coverage/
 /src/*/gen_table
 /build/
 /tmp/

util/build-run-test-coverage-linux.sh

@@ -0,0 +1,115 @@
+#!/usr/bin/env bash
+
+# spell-checker:ignore (env/flags) Ccodegen Cinstrument Coverflow Cpanic Zpanic
+# spell-checker:ignore PROFDATA PROFRAW coreutil librairies nextest profdata profraw rustlib
+
+# This script will build, run and generate coverage reports for the whole
+# testsuite.
+# The biggest challenge of this process is managing the overwhelming generation
+# of trace files that are generated after EACH SINGLE invocation of a coreutil
+# in the testsuite. Moreover, because we run the testsuite against the multicall
+# binary, each trace file contains coverage information about the WHOLE
+# multicall binary, dependencies included, which results in a 5-6 MB file.
+# Running the testsuite easily creates +80 GB of trace files, which is
+# unmanageable in a CI environment.
+#
+# A workaround is to run the testsuite util per util, generate a report per
+# util, and remove the trace files. Therefore, we end up with several reports
+# that will get uploaded to codecov afterwards. The issue with this
+# approach is that the `grcov` call, which is responsible for transforming
+# `.profraw` trace files into a `lcov` file, takes a lot of time (~20s), mainly
+# because it has to browse all the sources. So calling it for each of the 100
+# utils (with --all-features) results in an absurdly long execution time
+# (almost an hour).
+
+# TODO: Do not instrument 3rd party librairies to save space and performance
+
+# Exit the script if an unexpected error arise
+set -e
+# Treat unset variables as errors
+set -u
+# Print expanded commands to stdout before running them
+set -x
+
+ME="${0}"
+ME_dir="$(dirname -- "$(readlink -fm -- "${ME}")")"
+REPO_main_dir="$(dirname -- "${ME_dir}")"
+
+# Features to enable for the `coreutils` package
+FEATURES_OPTION=${FEATURES_OPTION:-"--features=feat_os_unix"}
+COVERAGE_DIR=${COVERAGE_DIR:-"${REPO_main_dir}/coverage"}
+
+LLVM_PROFDATA="$(find "$(rustc --print sysroot)" -name llvm-profdata)"
+
+PROFRAW_DIR="${COVERAGE_DIR}/traces"
+PROFDATA_DIR="${COVERAGE_DIR}/data"
+REPORT_DIR="${COVERAGE_DIR}/report"
+REPORT_PATH="${REPORT_DIR}/total.lcov.info"
+
+rm -rf "${PROFRAW_DIR}" && mkdir -p "${PROFRAW_DIR}"
+rm -rf "${PROFDATA_DIR}" && mkdir -p "${PROFDATA_DIR}"
+rm -rf "${REPORT_DIR}" && mkdir -p "${REPORT_DIR}"
+
+#shellcheck disable=SC2086
+UTIL_LIST=$("${ME_dir}"/show-utils.sh ${FEATURES_OPTION})
+
+export CARGO_INCREMENTAL=0
+export RUSTFLAGS="-Cinstrument-coverage -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
+export RUSTDOCFLAGS="-Cpanic=abort"
+export RUSTUP_TOOLCHAIN="nightly-gnu"
+export LLVM_PROFILE_FILE="${PROFRAW_DIR}/coverage-%m-%p.profraw"
+
+# Disable expanded command printing for the rest of the program
+set +x
+
+run_test_and_aggregate() {
+    echo "# Running coverage tests for ${1}"
+
+    # Build and run tests for the UTIL
+    cargo nextest run \
+        --profile coverage \
+        --no-fail-fast \
+        --color=always \
+        2>&1 \
+        ${2} \
+    | grep -v 'SKIP'
+    # Note: Do not print the skipped tests on the output as there will be many.
+
+    echo "## Tests for (${1}) generated $(du -h -d1 ${PROFRAW_DIR} | cut -f 1) of profraw files"
+
+    # Aggregate all the trace files into a profdata file
+    PROFDATA_FILE="${PROFDATA_DIR}/${1}.profdata"
+    echo "## Aggregating coverage files under ${PROFDATA_FILE}"
+    "${LLVM_PROFDATA}" merge \
+        -sparse \
+        -o ${PROFDATA_FILE} \
+        ${PROFRAW_DIR}/*.profraw \
+    || true
+    # We don't want an error in `llvm-profdata` to abort the whole program
+}
+
+for UTIL in ${UTIL_LIST}; do
+
+    run_test_and_aggregate \
+        "${UTIL}" \
+        "-p coreutils -E test(/^test_${UTIL}::/) ${FEATURES_OPTION}"
+
+    echo "## Clear the trace directory to free up space"
+    rm -rf "${PROFRAW_DIR}" && mkdir -p "${PROFRAW_DIR}"
+done;
+
+echo "Running coverage tests over uucore"
+run_test_and_aggregate "uucore" "-p uucore --all-features"
+
+echo "# Aggregating all the profraw files under ${REPORT_PATH}"
+grcov \
+    "${PROFDATA_DIR}" \
+    --binary-path "${REPO_main_dir}/target/debug/coreutils" \
+    --output-types lcov \
+    --output-path ${REPORT_PATH} \
+    --llvm \
+    --keep-only "${REPO_main_dir}"'/src/*'
+
+
+# Notify the report file to github
+echo "report=${REPORT_PATH}" >> $GITHUB_OUTPUT