How to: Develop shared packages across repos with some hot-reloading

The following will use the example of developing the shared library frontend-component-footer with the ability to see changes frontend-app-user-account, an application already set up with hot reloading.

Start by clearing removing the existing dependency (if it exists) from your hot-reloading application:

1. Remove '"@edx/frontend-component-footer": "^1.0.0",' from package.json in frontend-app-user-account.
2. Remove the dependency from frontend-app-user-account's node_modules.

cd ~/edx/frontend-app-user-account
rm -rf node_modules/\@edx/frontend-component-footer

Now add the dependency as a file pointer (still from the frontend-app-user-account directory):

1. Add the dependency

   # still in ~/edx/frontend-app-user-account
   npm install ../frontend-component-footer

   I tried "npm link" but it makes more invasive changes (sym links from both application and shared package to a global node module), it is more difficult to clean-up, and it had no benefits I could see.

2. Verify the package.json now contains '"@edx/frontend-component-footer": "file:../frontend-component-footer",'. 

   The following is for temporary local development only.  Be sure not to merge these dependency changes to master of any project.

Start the hot-reloading app:

# still in ~/edx/frontend-app-user-account
npm start
# load the app in the browser: http://localhost:1994/

Switch to the shared library.

1. Make a coding change to the footer shared component.

2. Build the shared library: 

   # Using a new terminal
   cd ~/edx/frontend-component-footer
   npm run build

3. Watch for the hot-reload in the browser.
4. Repeat as needed, or set up npm run watch to automatically rebuild your shared app.
   1. You may need to npm install npm-watch before running npm run watch. 
   2. You'll also have to add a watch config section and a watch script in you package.json file; see https://www.npmjs.com/package/npm-watch