require-precompute

Overview

Creating a (reasonable subset of a) Node.js-style require(name) function is pretty simple. If name starts with a period, it is a path relative to the file that called require. Just make the require used by each file keep track of the current path and you’re done.

If name does not start with a period, it is a node module. Usually it is located at currentModuleRoot + "/node_modules/" + name + "/index.js". So make require also keep track of the current module root. Simple.

However, there are two things that can complicate the above. The entry point of a module might not necessarily be called “index.js”. The name can be defined by the main property of the module’s package.json (if any). Moreover, the module might be located in a parent module’s node_modules directory, if they both share a dependency.

This module precomputes the two complications above, to make a require implementation simpler. You probably already had a build step; just add this precomputation to it.

The idea is to first look for info in the precomputed data; if it’s not there use the above steps.

Example output, from a hypothetical “x-lang” module:

{
  "./node_modules/helpers": {
    "": "lib/main"
  },
  "./node_modules/parser": {
    "source-map": "."
  },
  "./node_modules/parser/node_modules/helpers": {
    "": "main"
  },
  "./node_modules/parser/node_modules/tokenizer": {
    "helpers": "./node_modules/parser"
  },
  "./node_modules/compiler/node_modules/stringifier": {
    "": "stringify",
    "source-map": ".",
    "token-names": "./node_modules/compiler"
  },
  "./node_modules/source-map": {
    "": "lib/source-map"
  }
}

In the above example, x-lang depends on “helpers”, “source-map”, “parser” and “compiler” (and possibly other modules as well, but if so they didn’t need any data in the output). The parser also depends on helpers, but it cannot use the top-level helpers because it uses a different version. (Those two versions happen to use different files as the main entry-point.) Both the parser and the compiler’s stringifier depend on source-map, but unlike the helpers case they reuse the top-level source-map.

Installation

npm install require-precompute

var precompute = require("require-precompute")

Usage

var data = precompute(dir)

dir is the path to a directory to precompute.

data is a map between module root paths relative to dir and an object with info about that module:

• The value of the key "" (the empty string) is the path to the module’s entrypoint (if it has a package.json with the main property), relative to the module itself. The value has been path.normalized, and the .js suffix (if any) has been removed.
• All other keys are module names that the module depends on (according to its package.json’s dependencies property (if any)), that aren’t in the module’s own node_modules directory, but somewhere higher up. The values are the paths to those modules (relative to dir). The algorithm does not look outside dir for modules, and throws an error if it cannot be found there.

CLI

If you install this package globally, you’ll be able to run require-precompute [dir], which precomputes dir (defaults to the current directory) and prints the result to stdout.

License

The X11 (“MIT”) License.