liferay-npm-bundler

liferay-npm-bundler

A tool to process a Liferay portlet project to produce an OSGi bundle containing the needed npm dependencies so that it can be run when deployed to the Portal.

This tool is of a kind known as bundler, like browserify or webpack.

So, why writing another bundler? The main reason is that due to the modularity of Liferay Portal, several portlets that don't know each other in advance may need to cooperate to share their Javascript dependencies, so we cannot just deploy all Javascript in a single file like other bundlers do for web applications.

On the contrary, we need to bundle enough information so that the Portal can -when assembling a page- determine which packages must be used and how they are going to be shared among different portlets.

And that's where liferay-npm-bundler comes in handy.

Installation

npm install --save-dev liferay-npm-bundler

Usage

Usually liferay-npm-bundler is called in your package.json build script after all transpilation and processing has taken place.

To do so, you must have something similar to this in your package.json file:

"scripts": {
    "build": "... && liferay-npm-bundler"
}

Where the ... refers to any previous step you need to perform like, for example, transpiling your sources with Babel.

The output of liferay-npm-bundler is a directory that is suitable for deploying npm packages to Liferay Portal as explained in this project's root README file.

This tool is configured by means of a .npmbundlerrc file that must live inside the project's root folder. Continue reading to know how to write such file.

How it works internally

This tool assumes a Liferay portlet project as input and outputs its files to a build directory so that the standard Gradle build for portlets can carry on and produce an OSGi bundle that can be deployed to Liferay Portal.

To do so, it runs the project source files through the following workflow:

1. Copy project's package.json file to the output directory.
2. Traverse project's dependency tree to determine which packages are needed to run it.
3. For each dependency package:
   1. Copy package to output dir (in plain package@version format, as opposed to the standard node_modules tree format).
   2. Pre-process package with configured plugins.
   3. Run Babel through each .js file in the package with configured plugins.
   4. Post-process package with configured plugins.

The pre and post process steps are the same, they only differ in the moment when they are run (before or after Babel is run, respectively). In these steps, liferay-npm-bundler calls all the configured plugins so that they can perform transformations on the npm packages like, for instance, modifying its package.json file, or deleting or moving files.

Let's see an example with the following .npmbundlerrc file:

{
    "preset": "liferay-npm-bundler-preset-standard"
}

If we run liferay-npm-bundler with this file, it will apply the config file found in liferay-npm-bundler-preset-standard:

{
	"*": {
		"plugins": [
			"replace-browser-modules"
		],
		".babelrc": {
			"presets": ["liferay-standard"]
		}
	}
}

This states that for all npm packages (*) the pre-process phase (plugins) must run the replace-browser-modules plugin (if we wanted to run that plugin during the post phase, it should say post-plugins instead of plugins).

Looking at the documentation of replace-browser-modules plugin we can see that this plugin replaces Javascript modules as defined under the browser section of package.json files. This means that, for each npm package that our project has as dependency, liferay-npm-bundler will make sure that each one having a browser section in its package.json files will have its server side files replaced by their counterpart browser versions.

The next part of the .npmbundlerrc file specifies the .babelrc file to use when running Babel through the packages .js files. Please keep in mind that, in this phase, Babel is used to transform package files (for example to convert them to AMD format if necessary) not to transpile them (though, in theory, you could transpile them too if you wanted by configuring the proper plugins).

In this example, we use the liferay-standard preset, that applies the following plugins according to its documentation:

1. babel-plugin-normalize-requires
2. babel-plugin-transform-node-env-inline
3. babel-plugin-wrap-modules-amd
4. babel-plugin-name-amd-modules
5. babel-plugin-namespace-amd-define

Checking the documentation of these plugins we find out that Babel will:

1. Remove trailing .js strings from require() calls in our packages.
2. Replace occurrences of process.env.NODE_ENV by its literal value.
3. Wrap modules with an AMD define() call.
4. Give a canonical name to each AMD module based on its package and relative path inside it.
5. Prefix define() calls with Liferay.Loader..

Thus, after running liferay-npm-bundler on our project we will have a folder with all our npm dependencies extracted from the project's node_modules folder and modified to make them work on Liferay Portal under management of its Liferay AMD Loader.

Configuration

As said before, liferay-npm-bundler is configured placing a .npmbundlerrc file in your project's folder. The full structure of that file is:

{
    "exclude": {
        "*" : [
            (list of glob expressions excluding files)
        ],
        "(package name)" : [
            (same as for "*")
        ],
        "(package name)@(version)" : [
            (same as for "*")
        ]
    },
    "output": (relative path of output directory),
    "process-serially": (true|false),
    "*" : {
        "plugins": [
            (list of plugins)
		],
		".babelrc": {
            (standard .babelrc file)
		},
        "post-plugins": [
            (list of plugins)
		]
    },
    "(package name)" : {
        (same as for "*")
    },
    "(package name)@(version)" : {
        (same as for "*")
    }
    ...
}

Where:

• "exclude": defines files to be excluded from bundling from all or specific packages.

• "output": by default the bundled packages are written to build/resources/main/META-INF/resources, which is the standard Gradle output directory for resources, but it can be overriden for customized builds.

• "process-serially": defines whether to process dependency packages in parallel, leveraging Node.js asynchronous model, or one by one. The default value is false, so that everything gets processed in parallel, but you can disable it in case you get EMFILE errors due to opening too many files at the same time.

• (list of plugins): is a comma separated list of strings defining the liferay-npm-bundler plugins to call (note that the liferay-npm-bundler-plugin- part from the npm package name may be omitted).

• (standard .babelrc file): is a .babelrc file as defined in Babel's documentation that gets passed to Babel when called by liferay-npm-bundler.

• (package name): is a npm package name and the configuration under its scope will be only applied to packages with that name and any version.

• (version): is a npm package version and the configuration under its <package name>@<version> scope will be only applied to packages with that specific name and version.