feat: expressjs framework

[yanksyoon]

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Adds support for ExpressJS framework.

Key Decisions

• Support for bare and 24.04 only. Drop support for 22.04 (jammy)
  • Jammy comes with an old version of Node which does not support ?? operator commonly used in JS projects. This means that the projects initialized with express-generator tooling (assumed to be the case) would not work.
• Include runtime slices in the expressjs-framework/install-app > stage-packages part.
  • A separate expressjs-framework/runtime exists to cater to apt packages, since slices and apt packages cannot be used together by design. See [wishlist] separate stage-packages and stage-slices #785.
• Do not include user customizable part for runtime slices/packages in the template
  • There is an issue with the NPM plugin which conflicts with the lib directory of apt/slice installs. Remove the offering until the issue is resolved. See different contents or permissions error #790.
• Provide Ubuntu packaged Node/NPM by default, allow user to specify Node version if desired.
  • To follow the principles of Ubuntu LTS, by default use the NodeJS and NPM provided by apt/slices but allow users to customize the behavior through overriding the NPM plugin's npm-include-node and npm-node-version fields.
• Include all paths under the app/ directory.
  • Users should not include/add paths which are not desired in the app path (e.g. .env files)

[yanksyoon]

@medubelko

I'm still confused, sorry. The updated text reads:

the application is installed and run via NodeJS

Which is what I put in my suggestion:

Node.js installs and runs the app

Those two sentences are equivalent.

If the npm plugin performs the installation, the text should read:

... the npm plugin installs the app and Node.js, while Node.js runs the app.

Thanks for the comment! To clarify, the application "installation" is done by the NPM plugin - which involves two things:

1. Copying over the source files (done by rockcraft NPM plugin)
2. Installing the libraries in the package.json (done by npm tool)

Then, NodeJS provides a runtime in which the application is loaded and served. Would this make a difference in how we phrase the above?

[medubelko]

@yanksyoon

Would this make a difference in how we phrase the above?

Yes. :)

Let me try again:

In this case, the NPM plugin copies the app's files and installs its dependencies. Node.js then provides a runtime and launches the app.

For different possible values for the npm-node-version key...

[medubelko]

Thanks @yanksyoon!

[tigarmo]

Thanks! Approved pending the linting fix

[tigarmo]

I think the breakage came in from the update in main:

/home/docs/checkouts/readthedocs.org/user_builds/canonical-rockcraft/checkouts/784/docs/tutorial/expressjs.rst:24: CRITICAL: Problems with "include" directive path:
InputError: [Errno 2] No such file or directory: 'reuse/tutorial/setup.rst'.