Add rake set-version-to-timestamp task

This ensures the generated gem has a unique version number, so define
`RE2::VERSION` in a separate file to make this possible.

Rakefile

@@ -119,5 +119,28 @@ task gem_build_path do
   add_vendored_libraries
 end
 
+desc "Temporarily set VERSION to a unique timestamp"
+task "set-version-to-timestamp" do
+  # this task is used by bin/test-gem-build
+  # to test building, packaging, and installing a precompiled gem
+  version_constant_re = /^\s*VERSION\s*=\s*["'](.*)["']$/
+
+  version_file_path = File.join(__dir__, "lib/re2/version.rb")
+  version_file_contents = File.read(version_file_path)
+
+  current_version_string = version_constant_re.match(version_file_contents)[1]
+  current_version = Gem::Version.new(current_version_string)
+
+  fake_version = Gem::Version.new(format("%s.test.%s", current_version.bump, Time.now.strftime("%Y.%m%d.%H%M")))
+
+  unless version_file_contents.gsub!(version_constant_re, "    VERSION = \"#{fake_version}\"")
+    raise("Could not hack the VERSION constant")
+  end
+
+  File.open(version_file_path, "w") { |f| f.write(version_file_contents) }
+
+  puts "NOTE: wrote version as \"#{fake_version}\""
+end
+
 task :spec    => :compile
 task :default => :spec

lib/re2.rb

@@ -11,3 +11,4 @@
 end
 
 require "re2/scanner"
+require "re2/version"

lib/re2/version.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+module RE2
+  VERSION = "1.7.0"
+end

re2.gemspec

@@ -1,8 +1,14 @@
+begin
+  require File.expand_path(File.join(File.dirname(__FILE__), "lib/re2/version"))
+rescue LoadError
+  puts "WARNING: Could not load RE2::VERSION"
+end
+
 Gem::Specification.new do |s|
   s.name = "re2"
   s.summary = "Ruby bindings to re2."
   s.description = 'Ruby bindings to re2, "an efficient, principled regular expression library".'
-  s.version = "1.7.0"
+  s.version = defined?(RE2::VERSION) ? RE2::VERSION : "0.0.0"
   s.authors = ["Paul Mucur"]
   s.homepage = "https://github.com/mudge/re2"
   s.extensions = ["ext/re2/extconf.rb"]
@@ -15,6 +21,7 @@ Gem::Specification.new do |s|
     "lib/re2.rb",
     "lib/re2/scanner.rb",
     "lib/re2/string.rb",
+    "lib/re2/version.rb",
     "LICENSE.txt",
     "README.md",
     "Rakefile"

scripts/test-gem-build

@@ -0,0 +1,32 @@
+#! /usr/bin/env bash
+#
+#  run as part of CI
+#
+if [[ $# -lt 2 ]] ; then
+  echo "usage: $(basename $0) <output_dir> <platform>"
+  exit 1
+fi
+
+set -e -u
+
+OUTPUT_DIR=$1
+BUILD_NATIVE_GEM=$2
+
+test -e /etc/os-release && cat /etc/os-release
+
+set -x
+
+bundle install --local || bundle install
+bundle exec rake set-version-to-timestamp
+
+if [[ "${BUILD_NATIVE_GEM}" == "ruby" ]] ; then
+  # TODO we're only compiling so that we retrieve tarballs, we can do better.
+  bundle exec rake clean compile
+  bundle exec rake gem
+else
+  bundle exec rake gem:${BUILD_NATIVE_GEM}:builder
+fi
+
+mkdir -p ${OUTPUT_DIR}
+cp -v pkg/*.gem ${OUTPUT_DIR}
+ls -l ${OUTPUT_DIR}/*

scripts/test-gem-install

@@ -0,0 +1,33 @@
+#! /usr/bin/env bash
+#
+#  run as part of CI
+#
+if [[ $# -lt 1 ]] ; then
+  echo "usage: $(basename $0) <gems_dir> [install_flags]"
+  exit 1
+fi
+
+GEMS_DIR=$1
+shift
+INSTALL_FLAGS=$*
+
+test -e /etc/os-release && cat /etc/os-release
+
+set -e -x -u
+
+pushd $GEMS_DIR
+
+  gemfile=$(ls *.gem | head -n1)
+  ls -l ${gemfile}
+  gem install --no-document ${gemfile} -- ${INSTALL_FLAGS}
+  gem list -d re2
+popd
+
+if [ -n "${BUNDLE_APP_CONFIG:-}" ] ; then
+  export BUNDLE_CACHE_PATH="${BUNDLE_APP_CONFIG}/cache"
+fi
+
+bundle install --local || bundle install
+
+rm -rf lib ext # ensure we don't use the local files
+rake spec