Cleanly try requiring optional dependencies
npm install may-requireSometimes you need to require() an optional dependency. If it can be loaded, you want to use it. Otherwise, you have other plans. Unfortunately, require() throws if it can't load a module. For an optional dependency that's just awkward.
~~~bash
npm install may-require
~~~
The prmary use case of may-require is to hold off on throwing any errors loading modules until we've had a chance to decide if we care:
~~~javascript
...
// true, indicating the default watchers
if (w === true) {
const [e1, nsfw] = mayRequire('./lib/watchers/nsfw.js');
const [e2, sane] = mayRequire('./lib/watchers/sane.js');
const w = nsfw || sane;
if (!w) {
let err = new Error('Unable to provide a default file watcher.');
err.chain = [e1, e2];
throw err;
}
return w;
}
// false means no watchers
return false;
...
~~~
By default, modules are required from the context of the calling file's directory - just like require() normally works. However, may-require allows you to specify a directory to require "from" if you need to:
~~~javascript
const [err, watcher] = mayRequire({
from: process.cwd()
})('watcher');
if (err) {
// why did we optionally require?
throw err;
}
return watcher;
~~~
may-require also allows you to "reload" modules
~~~javascript
const [e1, clone1] = mayRequire({
reload: true
})('clone-me');
const [e2, clone2] = mayRequire({
reload: true
})('clone-me');
if (clone1 !== clone2) {
console.log('They look the same, but are not the same.');
}
~~~
Returns a function which will optionally require() a module using the supplied options. This is useful if you'd like to optionally require more than one module using the same options.
Optionally require()s the moduleId using the default options.
Optionally require()s the moduleId using the specified options.
#### options
##### from
The directory path from which to resolve the moduleId. This is particularly relevant for relative local module paths, but may also impact which node_modules folders are checked.
##### reload
A flag indicating whether a cached version of the module _should be ignored_ and a new copy loaded.
+ optional - requires relative modules in the context of process.cwd(). Returns null for errors that are not rethrown by specifying an option.
+ optional-require - pass it require and get back a function that optionally requires from your module. Errors can be handled via callback options.
+ tyr-require - optionally takes require as a second parameter. Errors must be obtained through tryRequire.lastError().
Copyright (c) 2017 Aaron Madsen
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