@contrast/dep-hooks
v1.10.0
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Post hooks for Module.prototype.require
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@contrast/dep-hooks
Intercept calls to require
in order to modify or replace exports.
Usage
Class: DepHooks
Instantiation
const DepHooks = require('./lib');
const depHooks = new DepHooks();
The DepHooks
constructor accepts a pino
logger as an argument.
.resolve(descriptor, ...handlers)
Options:
descriptor
: This can be a string or an object describing the module you want to intercept. If a string is used, or if the version field of the descriptor isn't set, all versions of the described module will be matched. Descriptors can have aname
,version
, andfile
property.handlers
: The remaning arguments are the handlers which will be invoked when the described module isrequire
'd. Each handler is passed the exported module and metadata including the module's root directory and its name and version as seen in itspackage.json
file. If a handler returns a truthy value, then that value will replace the return value ofrequire
.
Note: Registered handlers run once per unique instance of an export matching a descriptor.
.install()
This will monkey-patch Module.prototype.require
so that exports can be
intercepted. The monkey-patching will only happen once regardless of how many
times this is invoked.
.uninstall()
This will reset Module.prototype.require
to its value before being
monkey-patched by the instance.
Examples
Use case: For express
versions greater than or equal to 4, intercept the
export of the package's lib/view.js
file (relative to the package's base
directory) and apply a tag to the exported function.
const DepHooks = require('./lib');
const depHooks = new DepHooks();
depHooks.resolve(
{
name: 'express',
version: '>=4',
file: 'lib/view.js',
},
(xport, metadata) => {
// Read from the package.json:
// - metadata.name
// - metadata.version
// Absolute path to file:
// - metadata.packageDir
// xport === function View() { /*...*/ }
xport['I was intercepted'] = true;
},
);
Use case: Intercept all versions of body-parser
and replace the exported
functions.
const DepHooks = require('./lib');
const depHooks = new DepHooks();
depHooks.resolve({ name: 'body-parser' }, (xport, metadata) => {
// Read from the package.json:
// - metadata.name
// - metadata.version
// Absolute path to file:
// - metadata.packageDir
// xport === function bodyParser() { /*...*/ }
return function bodyParserReplacement() {
/*...*/
};
});