Node.js/npm - dynamic service discovery in packages

Question

I was wondering whether Node.js/npm include any kind of exension mechanism comparable to Python setuptools' "entry points" .

So, in short:

• is there any way I can do dynamic discovery of services provided by other packages using npm?
• if not, what would be the best way to implement something similar? Specifying the extension name in the main module's configuration file seems to be the logical solution, but I wonder whether something "automatic" can be done.

Answer 1

I'm not aware of any builtin mechanism to do this.

One viable way of doing it yourself:
I made a small tool (Jumpstart) to quickly create project scaffolding from templates with placeholders, and I used a kind of plugin mechanism for that. It basically comes down to that the Jumpstart script searches for modules named jumpstart-* "adjacent" to where the module itself is installed. So it would work for both local and global installations. If installed locally, it would search the other local modules (on the same level) and if global, it searches the other global modules.

Note that here, "search" comes down to a simple fs.exists check to see if there's a Jumpstart template module with a particular name installed. However, nothing would stand in the way to actually get a full list of all installed packages matching the jumpstart-* pattern, and loading all at once. I could also search up the entire directory tree for node_modules directories and do the same. There's no point in doing this for this particular program, however.

See https://npmjs.org/package/jumpstart for docs.

The only limitation to this technique is that all modules must be named in a consistent fashion. Start with some string, end with some string, something like that. Any rogue packages polluting the namespace could be detected by doing further checks on a package contents: What files does it contain? What kind of object does its main module export? etc.

Brunch also uses a plugin mechanism. This one actually deals with file extensions, so is more relevant: https://github.com/brunch/brunch/wiki/Plugins . See for example source of the CoffeeScript plugin https://github.com/brunch/coffee-script-brunch/blob/master/src/index.coffee .