bazel/bazel_wrapper_script.bash

#!/bin/bash
# Copyright 2022 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# A wrapper script to run a Bazel binary with its pre-extracted
# install_base and its embedded JRE. It avoids extracting 164 MiB of
# data to the output_user_root the first time it is invoked, and
# unexpected conflicts with the installed JDK.
#
# Note that this script assumes there is a 'bazel-real' binary and an
# 'install_base' directory next to it. This is normally generated by
# the Fuchsia 'generate_bazel_install.py' script, or the corresponding
# LUCI recipe.
#
# IMPORTANT: The timestamps under install_base/ must be 10 years in the
# future, or Bazel will refuse to run. This is used as a way to check that
# the files have not been tampered with.

set -eo pipefail

# `readlink -f` that works on OSX too.
function get_realpath() {
    if [ "$(uname -s)" == "Darwin" ]; then
        local queue="$1"
        if [[ "${queue}" != /* ]] ; then
            # Make sure we start with an absolute path.
            queue="${PWD}/${queue}"
        fi
        local current=""
        while [ -n "${queue}" ]; do
            # Removing a trailing /.
            queue="${queue#/}"
            # Pull the first path segment off of queue.
            local segment="${queue%%/*}"
            # If this is the last segment.
            if [[ "${queue}" != */* ]] ; then
                segment="${queue}"
                queue=""
            else
                # Remove that first segment.
                queue="${queue#*/}"
            fi
            local link="${current}/${segment}"
            if [ -h "${link}" ] ; then
                link="$(readlink "${link}")"
                queue="${link}/${queue}"
                if [[ "${link}" == /* ]] ; then
                    current=""
                fi
            else
                current="${link}"
            fi
        done

        echo "${current}"
    else
        readlink -f "$1"
    fi
}

readonly BAZEL_WRAPPER_DIR="$(dirname "$(get_realpath "${BASH_SOURCE[0]}")")"
readonly BAZEL_INSTALL_DIR="${BAZEL_WRAPPER_DIR}"
readonly BAZEL_INSTALL_BASE="${BAZEL_INSTALL_DIR}"/install_base

# Bazel will refuse to run if the timestamps for BAZEL_INSTALL_BASE are
# not at least 10 years in the future. Our CIPD archive does not preserve
# input timestamps, even if they were set correctly by install.sh, so
# just reset them directly (this takes < 0.06s on Linux), and trying
# to do that conditionally leads to incremental build breakages on
# infra bots (see https://fxbug.dev/129051).
case $OSTYPE in
  linux*)
    # A future timestamp in a format supported by GNU touch, which does
    # not support the same format as BSD touch.
    FUTURE_TIMESTAMP="2042-07-29 00:00:00"
    touch -d "${FUTURE_TIMESTAMP}" $(find "${BAZEL_INSTALL_BASE}")
    ;;
  darwin*|*bsd)
    # A future timestamp that is supported by MacOS filesystems.
    # See https://apple.fandom.com/wiki/2040_date_limit
    FUTURE_TIMESTAMP=204002050000
    touch -t "${FUTURE_TIMESTAMP}" $(find "${BAZEL_INSTALL_BASE}")
    ;;
  *)
    echo >&2 "ERROR: Unsupported system: $OSTYPE"
    ;;
esac

exec "${BAZEL_INSTALL_DIR}/bazel-real" \
  --install_base="${BAZEL_INSTALL_DIR}/install_base" \
  --server_javabase="${BAZEL_INSTALL_DIR}/install_base/embedded_tools/jdk" \
  "$@"