Yari

!Testing
!Prod Build

Quickstart

Development on yari involves updating the machinery that renders MDN content
or improving the structure and styling of the MDN UI (e.g. the styling of the
header). If you are more interested in contributing to the MDN content, you
should check out the content repo README
instead.

Before you can start working with Yari, you need to:

1. Install git, Node.js, and
Yarn 1.

1. Fork
the MDN content and
yari repositories using the Fork button on
GitHub.

1. Clone the forked repositories to your computer using the following commands
(replace [your account] with the account you forked the repositories to):

git clone https://github.com/[your_account]/content.git
git clone https://github.com/[your_account]/yari.git

To run Yari locally, you'll first need to install its dependencies and build the
app locally. Do this like so:

cd yari
yarn install

See the troubleshooting section below if you run into
problems.

Now copy the .env-dist file to .env:

cp .env-dist .env

If you followed the instructions above and cloned the content repo as a
sibling of your yari repo, the CONTENT_ROOT environment variable is already
set and Yari will be able to find the content it needs to render.

At this point, you can get started. Run the following lines to compile required
files, start the Yari web server running, and open it in your browser:

yarn dev
open http://localhost:3000

If you prefer you can use yarn start, which will re-use any previously
compiled files; this is "riskier" but faster. yarn dev always ensures that
everything is up-to-date.

The yarn start command also starts a server with slightly different behavior —
it doesn't automatically reload when its source code files change, so use with
caution.

See also our reviewing guide for information on how to
review Yari changes.

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Firstly, thank you for your interest in contributing to Yari! We do have a few
requirements when it comes to pull requests:

1. Please make use of a
feature branch workflow.
2. We prefer if you use the
conventional commits format when
making pull requests.
3. Lastly, we require that all commits are signed. Please see the documentation
about signed commits
and
how to sign yours
on GitHub.

Thank you for your understanding! We look forward to your contributions.

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Periodically, the code and the content changes. Make sure you stay up-to-date
with something along the following lines (replace yari-origin with whatever
you called the remote location of the
original yari repo):

git pull yari-origin main
yarn
yarn dev

When you embark on making a change, do it on a new branch, for example
git checkout -b my-new-branch.

License

All source code is MPL-2.0.

For content, see its
license in the
mdn/content repository.

Supported Platforms

yari runs on Linux in CI, and when building for Production.

We also support Windows and MacOS, however we don't aim to proactively catch
issues with CI on those platforms. If bugs arise, we welcome issues being filed,
or PRs being opened to fix them.

How it works

Yari does a number of things, the most important of which is to render and serve
the MDN content found in the content repo.
Each document is stored as an index.md (recommended) or index.html file that
contains metadata presented as YAML
front-matter followed by
the document source.

The builder converts these "source files" into "build files" using a CLI tool
that iterates over the files, builds the HTML, and lastly packages it up with
the front-end code, ready to be served as static files.

Development

The yarn start command encapsulates the front-end dev server (on
) and the server (on ).

All the sub-commands of yarn start can be broken down and run individually if
you want to work more rapidly.

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If you configure an environment variable called EDITOR, either on your system
as a whole or in the root .env file, it can be used in the development server
to link to sources which, when clicked, open in your preferred editor/IDE. For
example, in the root of the repo you could run:

echo 'EDITOR=code' >> .env

Now clicking certain links will open files directly in the currently open VS
Code IDE (replace code in the above command with a different text editor name
if needed, e.g. atom or whatever). To test it, view any document on
and click the "Open in your editor" button.

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The server has two main jobs:

1. Simulate serving the site (e.g. from a server, S3 or a CDN).
2. Trigger builds of documents that haven't been built, by URL.

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All JavaScript and TypeScript code needs to be formatted with prettier and
it's easy to test this with:

yarn prettier-check

And conveniently, if you're not even interested in what the flaws were, run:

yarn prettier-format

When you ran yarn for the first time (yarn is an alias for yarn install)
it automatically sets up a git pre-commit hook that uses lint-staged — a
wrapper for prettier that checks only the files in the git commit.

If you have doubts about formatting, submit your pull request anyway. If you
have formatting flaws, the
pull request checks should catch it.

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We maintain the dependencies using Dependabot in GitHub but if you want to
manually upgrade them you can use:

yarn upgrade-interactive --latest

Building

The server builds content automatically (on-the-fly) when you're viewing
pages, but you can pre-emptively build all the content in advance if desired.
One potential advantage is that you can get a more complete list of all possible
"flaws" across all documents before you even visit them.

The most fundamental CLI command is:

yarn build

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Every index.html becomes two files:

- index.html — a fully formed and complete HTML file
- index.json — the state information React needs to build the page in the
client

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When building you can enable specific "flaw checks" and their level of handling.
Some flaws are "cosmetic" and some are more severe but they should never block a
full build.

More information about how to set flaws can be found in docs/envvars.md.

Essentially, the default is to _warn_ about any flaw and you can see those flaws
when using . For completed builds, all flaws are ignored.
This makes the build faster and there's also no good place to display the flaws
in a production-grade build.

In the future, we might make the default flaw level error instead. That
means that any new edits to (or creation of) any document will break in
continuous integration if there's a single flaw and the onus will be on you to
fix it.

Icons and logos

The various formats and sizes of the favicon are generated from the file
mdn-web-docs.svg in the repository root. This file is then converted to
favicons using realfavicongenerator.net. To
generate new favicons, edit or replace the mdn-web-docs.svg file and then
re-upload that to realfavicongenerator.net.

Contact

If you want to talk to us, ask questions, and find out more, join the discussion
on the
MDN Web Docs chat room on
Matrix.

Troubleshooting

Some common issues and how to resolve them.

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There are two options to resolve this.

1. Disable the watcher via
REACT_APP_NO_WATCHER

echo REACT_APP_NO_WATCHER=true >> .env

2. Increase max_user_watches:\
See

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We can't know for sure what's causing this error but speculate a bug in how
yarn fails to resolve if certain @babel helper libs should install its own
sub-dependencies. A sure way to solve it is to run:

rm -fr node_modules
yarn install

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The default server port :5042 might be in use by another process. To resolve
this, you can pick any unused port (e.g., 6000) and run the following:

echo SERVER_PORT=6000 >> .env

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Download and install:

Microsoft Visual C++ Redistributable for Visual Studio 2019 (
x86,
ARM64 )

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If you get errors while installing dependencies via yarn on a Mac, you may need
to install some additional packages. Check the error message for the package
name causing the problem.

1. First, install brew if you haven’t already

1. To fix problems with gifsicle:

brew install automake autoconf libtool

1. To fix problems with pngquant-bin:

brew install pkg-config

1. To fix problems with mozjpeg:

brew install libpng sudo ln -s
/opt/homebrew/Cellar/libpng/1.6.40/lib/libpng16.a /usr/local/lib/libpng16.a

You may need to adjust the path to libpng16.a depending on the version of
libpng you have installed.