Allow to install multiple gem versions

README.md

Multiple gem versions

While developing a serialization gem I needed to compare my current code with previous gem versions.

(Un)fortunately bundler does not allow to install several versions of the same gem to prevent conflicts on class names. The purpose of this script is to wrap a gem into a namespace/module named.

You should set in the main script:

• L7 TARGET_DIR: the dir where the gems will be extracted
• L8 PKG_DIR : the dir where the .gem files will be downloaded
• L11 GEM_SOURCE : public/private gem repository
• L12 GEM_NAME : the name of the gem
• L13 GEM_MAIN_MODULE : the name of the main module wrapping the gem
• L14 GEM_VERSIONS : array of gem versions to download

The output will allow you to use:

require 'v010-my_gem'
class MyClass < V010::MyGem
  # some code here 
end

You will be able to install multiple versions in your Gemfile with local paths:

# benchmark_app/Gemfile

# Current gem version in development
gem 'jsonschema_serializer', path: '../'
gem 'v005-jsonschema_serializer', path: '../versions/jsonschema_serializer-0.0.5'

multiple_gem_versions.sh

#!/usr/bin/env bash
set -e
IFS=$'\n\t'

# Directories
ROOT_PATH=$(pwd) # "$(git rev-parse --show-toplevel)"
TARGET_DIR="${ROOT_PATH}/versions"
PKG_DIR="${ROOT_PATH}/pkg"

# https://rubygems.org/downloads/jsonschema_serializer-0.1.0.gem
GEM_SOURCE="https://rubygems.org"
GEM_NAME="jsonschema_serializer"
GEM_MAIN_MODULE="JsonschemaSerializer"
GEM_VERSIONS=(
	"0.0.5"
	"0.1.0"
)

GEMSPEC="${GEM_NAME}.gemspec"

function reset_dir {
	rm -rf $1 || true
	mkdir -p $1
}

function unpack_gem {
  gem unpack $1 --target ${TARGET_DIR}
}

function fetch_gem {
	# $1 GEM_FILEPATH "${PKG_DIR}/$1.gem"
	# $2 GEM VERSION e.g. 0.1.0
	if [ ! -e $1 ]; then
		gem fetch ${GEM_NAME} \
		    --version $2 \
		    --source "${GEM_SOURCE}"
		mv "${GEM_NAME}-${GEM_VERSION}.gem" "${PKG_DIR}/"
  fi
}

function ised {
  # Ensure sed multi platform compatibility
  if [[ $OSTYPE =~ ^darwin ]]; then
    sed  -i '' $@
  else
    sed -i $@
  fi
}

function process_gem_version {
	# $1 GEM VERSION e.g. 0.1.0
	GEM_VERSION=$1
	GEM_VNAME="${GEM_NAME}-${GEM_VERSION}"
	GEM_FILEPATH="${PKG_DIR}/${GEM_VNAME}.gem"
	echo -e "Processing ${GEM_VNAME}"
	fetch_gem ${GEM_FILEPATH} ${GEM_VERSION}

	NORMALIZED_VERSION=${GEM_VERSION//./}

	GEM_DIR=$(echo ${GEM_VERSION} | sed 's/.gem//' | sed 's~pkg/~~')
  VERSION=$(echo ${GEM_DIR} | sed 's/zenrializer-//')


  unpack_gem ${GEM_FILEPATH}
  EXTRACTED_DIR="${TARGET_DIR}/${GEM_VNAME}"
  cd "${EXTRACTED_DIR}"

  NEW_GEM_NAME="v${NORMALIZED_VERSION}-${GEM_NAME}"
  NEW_GEM_MAIN_MODULE="V${NORMALIZED_VERSION}::${GEM_MAIN_MODULE}"
  NEW_MODULE="V${NORMALIZED_VERSION}::Zenrializer"

  echo -e "Processing .gemspec"

  # Remove references to the gem version and rename file
  NEW_GEMSPEC="${NEW_GEM_NAME}.gemspec"
  sed "/${GEM_NAME}\/version/d" ${GEMSPEC} > ${NEW_GEMSPEC}
  rm ${GEMSPEC}

  ised "s~${GEM_MAIN_MODULE}::VERSION~'${GEM_VERSION}'~" ${NEW_GEMSPEC}

  ised "s#${GEM_NAME}#${NEW_GEM_NAME}#" ${NEW_GEMSPEC}
  ised "s#${GEM_MAIN_MODULE}#${NEW_GEM_MAIN_MODULE}#" ${NEW_GEMSPEC}

  # Assuming that you are working from ${EXTRACTED_DIR}
  LIB_FILES=$(ls lib/*.rb)
  LIB_FILES+=($(ls lib/**/*.rb))
  for FILE in "${LIB_FILES[@]}"; do
  	echo -e "Processing ${FILE} ..."
    if [ "${FILE}" == "lib/${GEM_NAME}.rb" ]; then
      MODULE_DECLARATION="module V${NORMALIZED_VERSION}; end"
    	awk "NR==1{print \"$MODULE_DECLARATION\"}1" ${FILE} > "${FILE}.bak"
    	mv "${FILE}.bak" ${FILE}
    fi
    ised "s#${GEM_NAME}#${NEW_GEM_NAME}#" ${FILE}
    ised "s#${GEM_MAIN_MODULE}#${NEW_GEM_MAIN_MODULE}#" ${FILE}
  done
  # Reset LIB_FILES content
  LIB_FILES=()

  # Rename main file
  mv "lib/${GEM_NAME}.rb" "lib/${NEW_GEM_NAME}.rb"

  # Rename lib main directory
  mv "lib/${GEM_NAME}" "lib/${NEW_GEM_NAME}"

  cd ${ROOT_PATH}
}

function main {
	echo -e "Resetting target dir ..."
	reset_dir ${TARGET_DIR}
	# Launch this script prepending RESET_PKG=1 to
	# reset the local gem copy
	if [ ! -z "$RESET_PKG" ]; then
		echo -e "Resetting pkg dir ..."
		reset_dir ${PKG_DIR}
	fi
	echo -e "Fetching gem version ..."

	for GEM_VERSION in "${GEM_VERSIONS[@]}"; do
		process_gem_version ${GEM_VERSION}
	done
}

main