Package manager tips

The semantics of the Node.js require() function were designed to be general enough to support reasonable directory structures. Package manager programs such as dpkg, rpm, and npm will hopefully find it possible to build native packages from Node.js modules without modification.

In the following, we give a suggested directory structure that could work:

Let's say that we wanted to have the folder at /usr/lib/node/<some-package>/<some-version> hold the contents of a specific version of a package.

Packages can depend on one another. In order to install package foo, it may be necessary to install a specific version of package bar. The bar package may itself have dependencies, and in some cases, these may even collide or form cyclic dependencies.

Because Node.js looks up the realpath of any modules it loads (that is, it resolves symlinks) and then looks for their dependencies in node_modules folders, this situation can be resolved with the following architecture:

• /usr/lib/node/foo/1.2.3/: Contents of the foo package, version 1.2.3.
• /usr/lib/node/bar/4.3.2/: Contents of the bar package that foo depends on.
• /usr/lib/node/foo/1.2.3/node_modules/bar: Symbolic link to /usr/lib/node/bar/4.3.2/.
• /usr/lib/node/bar/4.3.2/node_modules/*: Symbolic links to the packages that bar depends on.

Thus, even if a cycle is encountered, or if there are dependency conflicts, every module will be able to get a version of its dependency that it can use.

When the code in the foo package does require('bar'), it will get the version that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar. Then, when the code in the bar package calls require('quux'), it'll get the version that is symlinked into /usr/lib/node/bar/4.3.2/node_modules/quux.

Furthermore, to make the module lookup process even more optimal, rather than putting packages directly in /usr/lib/node, we could put them in /usr/lib/node_modules/<name>/<version>. Then Node.js will not bother looking for missing dependencies in /usr/node_modules or /node_modules.

In order to make modules available to the Node.js REPL, it might be useful to also add the /usr/lib/node_modules folder to the $NODE_PATH environment variable. Since the module lookups using node_modules folders are all relative, and based on the real path of the files making the calls to require(), the packages themselves can be anywhere.