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How the Bundler Publishes npm Packages

When you deploy an OSGi bundle with the specified structure, its modules are made available for consumption through canonical URLs. To better illustrate resolved modules, the example structure below is the standard structure that the liferay-npm-bundler 1.x generates. It doesn’t have the namespaced packages that the 2.x version generates. The liferay-npm-bundler 2.0 overrides this de-duplication mechanism to implement isolated dependencies and imports, as explained below.

my-bundle/
- META-INF/
  - resources/
    - package.json
      - name: my-bundle-package
      - version: 1.0.0
      - main: lib/index
      - dependencies:
        
        isarray: 2.0.0
        
        isobject: 2.1.0
      - …
    - lib/
      - index.js
      - …
    - …
    - node_modules/
      - isobject@2.1.0/
        
        package.json
        
        name: isobject
        
        version: 2.1.0
        
        main: lib/index
        
        dependencies:
        
        isarray: 1.0.0
        
        …
        
        …
      - isarray@1.0.0/
        
        package.json
        
        name: isarray
        
        version: 1.0.0
        
        …
        
        …
      - isarray@2.0.0/
        
        package.json
        
        name: isarray
        
        version: 2.0.0
        
        …
        
        …

If you deploy the example OSGi bundle shown above, the following URLs are made available (one for each module):

note

The OSGi bundle ID (598) may vary.

Package De-duplication

Since two or more OSGi modules may export multiple copies of the same package and version, Liferay Portal must de-duplicate such collisions, by using a new concept called a resolved module.

A resolved module is the reference package exported to Liferay Portal’s frontend, when multiple copies of the same package and version exist. It’s randomly referenced from one of the several bundles exporting the same copies of the package.

Using the example above, for each group of canonical URLs referring to the same module inside different OSGi bundles, there’s another canonical URL for the resolved module. The example structure has the resolved module URLs shown below:

note

The OSGi bundle ID (598 in the example) is removed and module is replaced by resolved-module.

Next you can learn how the bundler (since version 2.0.0) isolates package dependencies. See What Changed Between liferay-npm-bundler 1.x and 2.x for more information on why this change was made.

Isolated Package Dependencies

A typical OSGi bundle structure generated with liferay-npm-bundler 2.x is shown below:

my-bundle/
- META-INF/
  - resources/
    - package.json
      - name: my-bundle-package
      - version: 1.0.0
      - main: lib/index
      - dependencies:
        
        my-bundle-package$isarray: 2.0.0
        
        my-bundle-package$isobject: 2.1.0
      - …
    - lib/
      - index.js
      - …
    - …
    - node_modules/
      - my-bundle-package$isobject@2.1.0/
        
        package.json
        
        name: my-bundle-package$isobject
        
        version: 2.1.0
        
        main: lib/index
        
        dependencies:
        
        my-bundle-package$isarray: 1.0.0
        
        …
        
        …
      - my-bundle-package$isarray@1.0.0/
        
        package.json
        
        name: my-bundle-package$isarray
        
        version: 1.0.0
        
        …
        
        …
      - my-bundle-package$isarray@2.0.0/
        
        package.json
        
        name: my-bundle-package$isarray
        
        version: 2.0.0
        
        …
        
        …

Note that each package dependency is namespaced with the bundle’s name (my-bundle-package$ in the example structure). This lets each project load its own dependencies and avoid potential collisions with projects that export the same package. For example, consider the two widget projects below:

my-widget
- package.json
  - dependencies:
    - a-library 1.0.0
    - a-helper 1.0.0
- node_modules
  - a-library
    - version: 1.0.0
    - dependencies:
      - a-helper ^1.0.0
  - a-helper
    - version: 1.0.0
another-widget
- package.json
  - dependencies:
    - a-library 1.0.0
    - a-helper 1.2.0
- node_modules
  - a-library
    - version: 1.0.0
    - dependencies:
      - a-helper ^1.0.0
  - a-helper
    - version: 1.2.0

In this example, a-library depends on a-helper at version 1.0.0 or higher (note the caret ^ expression in the dependencies). The bundler implements isolated dependencies by prefixing the name of the bundle to the modules, so that my-widget gets its a-helper at 1.0.0, while another-widget gets its a-helper at 1.2.0.

The dependencies isolation not only avoids collisions between bundles, but also makes peer dependencies behave deterministically as each widget gets what it had in its node_modules folder when it was developed.

Now that you understand how namespacing modules isolates bundle dependencies, avoiding collisions, you can learn about de-duplication next.

De-duplication through Importing

Isolated dependencies are useful, but sometimes sharing the same package between modules would be more beneficial. To do this, the liferay-npm-bundler can import packages from an external OSGi bundle, instead of using your own. Now you can put shared dependencies in one project and reference them from the rest.

For example, if three widgets, my-toolbar, my-menu, and my-content, compose the home page of your site, these widgets depend on the fake, but awesome, Wonderful UI Components (WUI) framework. This quite limited framework contains only three packages:

component-core
button
textfield

Since the bundler namespaces each dependency package with the widget’s name by default, you end up with three namespaced copies of the WUI package on the page. This is not what you want. Since they share the same package, you can create a fourth bundle that contains the WUI package and import the WUI package in the three widgets. This results in the structure below:

my-toolbar/
- .npmbundlerrc
  - config:
    - imports:
      - wui-provider:
        
        component-core: ^1.0.0
        
        button: ^1.0.0
        
        textfield: ^1.0.0
my-menu/
- .npmbundlerrc
  - config:
    - imports:
      - wui-provider:
        
        component-core: ^1.0.0
        
        button: ^1.0.0
        
        textfield: ^1.0.0
my-content/
- .npmbundlerrc
  - config:
    - imports:
      - wui-provider:
        
        component-core: ^1.0.0
        
        button: ^1.0.0
        
        textfield: ^1.0.0
wui-provider/
- .package.json
  - name: wui-provider
  - dependencies:
    - component-core: 1.0.0
    - button: 1.0.0
    - textfield: 1.0.0

The bundler switches the namespace of certain packages, thus pointing them to an external bundle. Say that you have the following code in my-toolbar widget:

var Button = require('button');

By default, the bundler 2.x transforms this into the following when not imported from another bundle:

var Button = require('my-toolbar$button');

But, because button is imported from wui-provider, it is instead changed to the value below:

var Button = require('wui-provider$button');

Also, a dependency on wui-provider$button at version ^1.0.0 is included in my-toolbar’s package.json file so that the loader finds the correct version. That’s all you need. Once wui-provider$button is required at runtime, it jumps to wui-provider’s context and loads the subdependencies from there on, even if code is executed from my-toolbar. This works because, as you can imagine, wui-provider’s modules are namespaced too, and once you load a module from it, it keeps requiring wui-provider$ prefixed modules all the way down.

Strategies When Importing Packages

De-duplication by importing is a powerful tool, but you must design a versioning strategy so that you don’t run into errors.

First, you must decide if you want to declare imported dependencies only in the .npmbundlerrc file or in the package.json too. Listing an imported dependency in .npmbundlerrc is enough; even if it’s not in your node_modules folder the loader finds it at runtime. Listing an imported dependency in .npmbundlerrc is enough; even if it isn’t present in your node_modules folder the loader finds it at runtime. If you have previous experience with dynamic linking support in standard operating systems, think of it as a DLL or shared object.

You may need to install your dependencies in node_modules too if you use them for tests, or if they contain types needed to compile (like in Typescript), etc. If that is the case, you can place them in the dependencies or devDependencies section of your package.json. If you list them under the latter, they are excluded automatically from the output bundle by the liferay-npm-bundler. Otherwise, you must exclude them in the .npmbundlerrc file so they don’t redundantly appear in the output.

If you list dependencies both in package.json and .npmbundlerrc, decide how to keep versions in sync. The best advice is to use the same version constraints in both files, but you may decide not to do so if it is necessary. For example, imagine that you import one of your dependencies from another bundle during runtime to run tests. Say you are using version constraint ^{1.5.1. It would be desirable that if you have tested your code with a version >=1.5.1 and <2.0.0 (that’s what}1.5.1 means), you get a compatible version during runtime. Thus, you would declare the dependency with ^1.5.1 in .npmbundlerrc too.

However, there are times when you may want to be more lenient, and you may need to get a lower version (1.4.0 for example) during runtime, even if you are developing against ^{1.5.1. In that case, you can declare}1.5.1 in your package.json and ^1.0.0 in .npmbundlerrc.

In the end, it’s up to you to decide how you want to handle your dependencies: