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Packages and style conventions

ยท 6 min read

Style conventions are always a topic for debate. Everyone agrees that conventions are good, and simultaneously prefers their own conventions. Tools like Prettier were built in that particular kind of bikeshed. In that spirit, allow me to introduce two tools that consolidate our JavaScript conventions.

EDIT MARCH 28, 2019 - While the concepts in this post still very much hold true, the code-style and packages (with the exception of packages exec) are being deprecated. Please use d2 instead of these older stand-alone tools where possible!

code-style comes with two scripts, code-style.js and commit-style.js.

code-style.js does a couple of things related to your codebase:

  • Runs Prettier on your staged, or all with --all, files with the DHIS2 Prettier configuration.
  • Removes any existing Prettier configuration.
  • Copies the official Prettier config file to the repo so tools can find it by default.
  • Adds the official Browerslist config file to the repo so other tools (Babel, etc.) can easily find it.
  • Stages all the re-formatted files.

commit-style.js orients its existence around making sure that commit messages follow a structured format:

  • Passes the commit message through commitlint and validates it with our chosen configuration.

code-style is designed to function standalone and as a plugin to packages, so even if you are not using packages to manage your app or lib, it is still advisable to use code-style to format your code and commit messages.

If you are using packages then you get access to code-style functionality automatically. If you want to only use code-style, see the README for specific instructions.

2 - packages

packages is a commandline tool that comes with a set of built-in commands and extends its functionality with plugins.

When a project is setup using packages and e.g. Husky to manage Git hooks, the benefits are:

  • โค๏ธ Standardised code formatting
  • ๐Ÿ’š Structured commit messages
  • ๐Ÿ’™ Automatic CHANGELOG generation
  • ๐Ÿ’› Automatic semantic version bumps
  • ๐Ÿ’œ Monorepo management with flatpaks

Since packages includes code-style, we can focus on setting up the former.

General setup

If you set up the scripts property in package.json as below you can simplify your life significantly, but you are free to use the packages commands manually as well if you install packages globally.

npm install --save-dev @dhis2/packages
npm install --save-dev husky

Regardless of whether the project is a monorepo or a standard repo and whether it uses Yarn or NPM you will want to set up your package.json with the following properties:

"scripts": {
"format": "packages code-style",
"release": "packages release"
"husky": {
"hooks": {
"commit-msg": "packages commit-style",
"pre-commit": "packages code-style"

For more information about how to setup packages for a monorepo check the docs in the packages repo.

There is also information on how to migrate from Lerna to Packages.

Apply the code style

The default operational mode of code-style is to only format your staged files to allow you to split up commits without interference from the tool staging changes that were meant to be deferred.

Of course, this won't do when the intention is to convert a project to use the standard formatting rules. To apply the code format to all files in a project:

packages code-style --all

Now the changes can be commited.

Generating an initial CHANGELOG

After the general setup has been completed you can generate a changelog for your repo.

The first time you run this command, use the --first-release flag:

packages release --first-release

This generates the file in the repo, but does not bump the version for the project.

As you create new commits according to the commit-style format, the changelog can be filled out automatically based on the information embedded in the VCS history.

We adhere to the conventional commit standard.

Writing commit messages

In general all commit messages must conform to the format:

type(scope?): subject # note: scope is optional

Some real world examples would be:

A bugfix for the headerbar component in d2-ui:

fix(headerbar): allow logo to collapse on smaller screens

A commit message for a feature containing subject, body, and footer:

feat: implement new schemas

New schemas which require bla bla bla

fixes DHIS2-xxxx

A breaking change must include the string BREAKING CHANGE: followed by a description in either the body or the footer of the message:

feat: update to new api version

BREAKING CHANGE: new api /v31 used to access features x, y, and z needed
to fix DHIS2-xxxx

Cut a release

When the time comes to cut a new release, run the command:

packages release

This command will do the following:

1. Set a new versionโ€‹

This scans your commits for information about what version to bump the package.json to. Based on that information, a new version will be chosen automatically; breaking changes bump the major position, features bump the minor position, and fixes bump the patch position.

2. Generate the CHANGELOGโ€‹

It also generates a new with sections for the different changes, an example can be found in ui/

3. Commit changed filesโ€‹

The package.json and are commited.

4. Tag the releaseโ€‹

Finally, packages creates the tags for the release.

Control handed back to developerโ€‹

At this point, all changes are done to the local Git repo so feel free to check if everything looks right, and once you are ready to trigger the build process (which publishes the release automatically) run the command:

git push --follow-tags origin master

Once the tags land on Github, Travis will pick up the tag and start building, and eventually publish the build artifact to NPM using the deploy-build tool (which will get its own blog post shortly).

Recap ๐Ÿ˜ค

At this point the project is set up to:

  • Re-format any staged code before it's commited
  • Validate the commit message before it's commited
  • Automatically cut a release
  • Optional: Monorepo dependency management

That's it! ๐ŸŽ‰

Thanks to @jenniferarnesen and @Birkbjo for corrections and improvements to the text.