Use bin/run to run Swift commands found in a project's bin/ directory

run.sh

#!/bin/sh
#
# bin/run: Run Swift commands in a project's bin/ directory.
#
# Drop-in replacement for `swift run`.
# Adds caching of built products based on source file contents.
#
# Usage:
#     bin/run <command [options]>   # Run named command defined in `bin/Package.swift`
#
#     bin/run --build               # Build out of date products
#     bin/run --clean               # Clean built products
#     bin/run --resolve             # Resolve package dependencies
#     bin/run --update              # Update package dependencies
#     bin/run --shasum              # Compute the cache key based on current source file contents

set -e

if [ -z ${SWIFTPM_CACHE_KEY_PATH+x} ]; then
  export SWIFTPM_CACHE_KEY_PATH=bin/.build/contents.sha
fi

cache_key() {
  (
    cd bin
    cat Package.resolved src/**/*.swift | shasum | cut -f1 -d' '
  )
}

cache_valid() {
  [ "$IGNORE_CACHE" != 1 ] \
    && [ -f "$SWIFTPM_CACHE_KEY_PATH" ] \
    && [ "$(cat "$SWIFTPM_CACHE_KEY_PATH")" = "$(cache_key)" ]
}

write_cache_key() {
  if [ -n "$SWIFTPM_CACHE_KEY_PATH" ]; then
    mkdir -p "$(dirname "$SWIFTPM_CACHE_KEY_PATH")"
    cache_key > "$SWIFTPM_CACHE_KEY_PATH"
  fi
}

swift() {
  # subshell provides local variable scoping
  (
    swift_subcommand="$1"; shift
    env SDKROOT=macosx swift "$swift_subcommand" --package-path bin "$@"
  )
}

build_if_necessary() {
  if ! cache_valid; then
    swift build
    write_cache_key
  fi
}

if [ $# = 0 ]; then
  echo >&2 "bin/run: Specify a subcommand to run."
  exit 1
fi

case "$1" in
  --build)
    build_if_necessary
    ;;
  --clean)
    swift package clean
    ;;
  --resolve)
    swift package resolve
    ;;
  --update)
    shift
    swift package update "$@"
    ;;
  --shasum)
    cache_key
    ;;
  *)
    build_if_necessary
    swift run --skip-build "$@"
    ;;
esac