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:
-
Fork the MDN content and yari repositories using the Fork button on GitHub.
-
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 Take a note of the file path to the location where you've cloned that repo before moving on.
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
Now run the following command to create a .env
file inside your yari
repo
root and set the CONTENT_ROOT
environment variable equal to the path to the
content
repo. This is so the Yari app can find the content it needs to render.
You'll need to replace /path/to/mdn/content/files
with the path to the
/files
folder inside your clone of the content
repo:
echo CONTENT_ROOT=/path/to/mdn/content/files >> .env
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.
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
.
All source code is MPL-2.0.
For content, see its license in the mdn/content repository.
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.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.
The yarn start
command encapsulates the front-end dev server
(on http://localhost:3000) and the server
(on http://localhost:5000).
All the sub-commands of yarn start
can be broken down and run individually
if you want to work more rapidly.
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
http://localhost:3000 and click the "Open in your editor" button.
The server
has two main jobs:
- Simulate serving the site (e.g. from a server, S3 or a CDN).
- Trigger builds of documents that haven't been built, by URL.
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
pretty-quick
— 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.
We maintain the dependencies using Dependabot
in GitHub but if you want
to manually upgrade them you can use:
yarn upgrade-interactive --latest
ngrok
allows you to start an HTTP proxy
server from the web into your Yari server. This can be useful for testing
your current build using external tools like BrowserStack, WebPageTest, or
Google Translate, or to simply show a friend what you're up to. Obviously
it'll never be faster than your uplink Internet connection but it should
be fairly feature-complete.
- Create in account on Ngrok.com
- Download the executable
- Start your Yari server with
yarn start
in one terminal - Start the
ngrok
executable with:/path/to/your/ngrok http 5000
This will display something like this:
Session Status online
Account (Plan: Free)
Version 2.3.35
Region United States (us)
Web Interface http://127.0.0.1:4040
Forwarding http://920ba2108da8.ngrok.io -> http://localhost:5000
Forwarding https://920ba2108da8.ngrok.io -> http://localhost:5000
Connections ttl opn rt1 rt5 p50 p90
0 0 0.00 0.00 0.00 0.00
Now, take that "Forwarding" URL (https://920ba2108da8.ngrok.io
in this
example) and share it.
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
Every index.html
becomes two files:
index.html
— a fully formed and complete HTML fileindex.json
— the state information React needs to build the page in the client
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 http://localhost:3000. 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.
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.
Some common issues and how to resolve them.
There are two options to resolve this.
-
Disable the watcher via
REACT_APP_NO_WATCHER
echo REACT_APP_NO_WATCHER=true >> .env
-
Increase
max_user_watches
:
See https://github.com/guard/listen#increasing-the-amount-of-inotify-watchers
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
The default server port :5000
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