status-mobile/nix/scripts/node_modules.sh

#!/usr/bin/env bash

#
# Check if we need to copy node_modules.
# (e.g. in case it has been modified after last copy)
#
# The reasoning for a (mostly) read-only node_modules folder:
#   ideally we’d symlink the folder directly to the Nix store
#   so that we’re guaranteed to have a reproducible source.
#   Unfortunately react-native wants to build some stuff after the fact
#   and this is incompatible with the concept of a pure Nix package.
#   Therefore we copy the whole source to the repo directory,
#   allow writing only on the folders where it is absolutely required,
#   and therefore we still keep some peace of mind that the rest
#   of node_modules is unchanged the rest of the time.
#

set -Eeuo pipefail

function replaceNodeModules() {
  local deps="$1"
  local targetNodeModules="$2"
  local needCopyModules=1
  local sentinelFilePath="$targetNodeModules/.copied~"

  # Check if node_modules exists and is valid
  if [ -d "$targetNodeModules" ]; then
    if [ -f "$sentinelFilePath" ]; then
      existingPath="$(cat $sentinelFilePath)"
      if [ "${existingPath}" != "${deps}" ]; then
        echo "Yarn modules changed, copying new version over"
      else
        echo "Checking for modifications in node_modules..."
        modifiedFiles=(
          $(find $targetNodeModules -writable -type f -newer $sentinelFilePath \
                -not \( -path "$targetNodeModules/react-native/ReactAndroid/build/*" -prune \
                      -o -path "$targetNodeModules/*/android/build/*" -prune \) -print) )
        if [ ${#modifiedFiles[@]} -eq 0 ]; then
          needCopyModules=0
          echo "No modifications detected."
        else
          echo "Modifications detected in ${#modifiedFiles[@]} files:"
          for f in ${modifiedFiles[@]}; do
            echo "- $(realpath --relative-to=$STATUS_REACT_HOME $f)"
          done
        fi
      fi
    fi
    if [ $needCopyModules -eq 1 ] && [ -d $targetNodeModules ]; then
      chmod u+w -R $targetNodeModules
      rm -rf $targetNodeModules
    fi
  fi

  # Replace node_modules if necessary
  if [ ! -d "$targetNodeModules" ]; then
    local tmpNodeModules=$(mktemp -d)
    echo "Copying node_modules from Nix store:"
    echo " - ${deps}"
    export TIMEFORMAT="Done in: %Es"
    trap "[ -d \"${tmpNodeModules}\" ] && chmod -R u+w \"${tmpNodeModules}\" && rm -rf \"${tmpNodeModules}\"" ERR INT HUP
    # WARNING: The -L here is crucial to let Metro find modules.
    time cp -LRf ${deps}/node_modules/. "${tmpNodeModules}"
    chmod -R u+w "${tmpNodeModules}"
    # WARNING: We can't de-reference .bin symlinks
    cp -Rf ${deps}/node_modules/.bin/. "${tmpNodeModules}/.bin/"
    mv -f "${tmpNodeModules}" "${targetNodeModules}"

    echo -n "${deps}" > "${sentinelFilePath}"
    trap - ERR INT HUP
  fi
}

deps="$1"
[ -d $deps ] || exit 1

nodeModulesDir="$STATUS_REACT_HOME/node_modules"

export -f replaceNodeModules
mkdir -p "$nodeModulesDir/"
# Leverage flock (file lock) utility to create an exclusive lock on node_modules/ while running replaceNodeModules
flock "$nodeModulesDir/" sh -c "replaceNodeModules $deps $nodeModulesDir"