$: npm publish -if-needed

Publish a new version of your libraries on NPM only if changes have been made.

Photo by Milad Fakurian on Unsplash

I’m not particularly strong in DevOps, but a few weeks ago, I found myself working on improving a monorepo that contains multiple JavaScript libraries published to NPM. Until then, we had been publishing all libraries with every release, whether they were modified or not. Surprisingly, there wasn’t an option to skip unmodified libraries. So, inspired by a GitHub thread, I decided to implement a small script that accomplishes this task. In this short blog post, I’m sharing the script with you.

Script

The script that publishes a library only if it has been modified is as follows.

#!/usr/bin/env bash

function publish_npm() {
  local lib=$1

  LOCAL_SHASUM=$(npm pack -w packages/"$lib" --json | jq '.[] | .shasum' | sed -r 's/^"|"$//g')

  NPM_TARBALL=$(npm show @dfinity/"$lib" dist.tarball)
  NPM_SHASUM=$(curl -s "$NPM_TARBALL" 2>&1 | shasum | cut -f1 -d' ')

  if [ "$LOCAL_SHASUM" == "$NPM_SHASUM" ]; then
    echo "No changes in $lib need to be published to NPM."
  else
    npm publish --workspace=packages/"$lib" --provenance --access public
  fi
}

# Tips: libs use by other libs first
LIBS=utils,ledger-icrc,ledger-icp,nns-proto,nns,sns,cmc,ckbtc,ic-management

for lib in $(echo $LIBS | sed "s/,/ /g"); do
  publish_npm "$lib"
done

So, what does it do?

First, I use a list of libraries that should be published, as seen in the variable LIBS. I could have simply listed all the packages present in the workspace with a bash command, but there might be some folders that should be skipped. Therefore, I decided to use a manual list.

Note that I am using npm workspaces.

For each of these libraries, a function called publish_npm is executed.

To begin, the function calculates the shasum of the library as if it were to be published. It accomplishes this by using the npm command pack with the --json option. This command generates JSON output, including various information:

[
  {
    "id": "@dfinity/utils@1.0.0",
    "name": "@dfinity/utils",
    "version": "1.0.0",
    "size": 35763,
    "unpackedSize": 124014,
    "shasum"…