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Offline generation of Angular CLI projects with Yarn

There are situations when the ability to generate new Angular CLI projects from the locally installed packages is quite useful, for example:

  • You’re running a live workshop at a conference in a hotel and the students have to install project dependencies multiple times. When 20-30 people are installing Angular dependencies at the same time on a hotel’s connection, it can take three minutes or more.
  • You’re on a long flight and want to try something new with Angular.

In this post, I’ll show you how to generate Angular CLI projects in a disconnected mode.

First of all, I don’t use npm. I use Yarn for two main reasons:

  1. Yarn is faster than npm (including npm 5)
  2.  Yarn creates a file yarn.lock that keeps track of the exact version of packages installed. For example, if package.json has a dependency “@angular/core”: “^5.0.0”, running yarn install today would include the version of 5.1.0 of this package. If you want to make sure that all devs in your team use this version even if 5.2.0 is available, push yarn.lock in the source control repo, and everyone who pulls the code will get 5.1.0. Reproducible builds are guaranteed. While npm 5 also creates a file package-lock.json, it doesn’t guarantee the same versions for all developers.

To configure Yarn as a default package manager for Angular CLI, run the following command:

ng set --global packageManager=yarn

Now let’s see how to create a local directory (a.k.a yarn offline mirror) with cached packages so Yarn can use it without the need to connect to the Internet.

Perform the following steps before boarding the plane while the Internet connection is still available.

1. Configure the directory for locally cached packages by running this command:

yarn config set yarn-offline-mirror ~/npm-packages-offline-cache

This will create a file .yarnrc in the user’s directory on your computer. In my case (I use MAC OS), this command creates the file .yarnrc with the following content

# yarn lockfile v1

lastUpdateCheck 1512857190418
yarn-offline-mirror "/Users/yfain11/npm-packages-offline-cache"

2. Generate a new project with Angular CLI without installing dependencies:

ng new hello-cli --skip-install

3. Copy the file .yarnrc into the newly generated directory hello-cli

4. Change directory to hello-cli:

cd hello-cli

5. Install the project dependencies using Yarn:

yarn install

Important: Make sure that there is no file yarn.lock when you run this command for the first time.

This command not only will install dependencies in the node_modules directory but will also create a directory npm-packages-offline-cache in your user’s directory. This directory will contain about a thousand of compressed package files required for the offline installation. These are gzipped files with extension .tgz. This is your Yarn offline mirror with npm packages.

6. Just in case, clear existing yarn cache to make sure we’ll be using only the files from the mirror:

yarn cache clear

Now let’s board the plane. Turn off the wi-fi or unplug the network wire. Our aircraft is airborne.

In the hello-cli directory, run the following command:

yarn install --offline

Yarn will install all the dependencies from the offline mirror. Now you can create as many Angular CLI projects as you need without being connected:

1. Generate a new project:

ng new hello-cli2 --skip-install 

2. Copy the file .yarnrc into the hello-cli2 directory

3. Change to the project directory

cd hello-cli2

4. Run the offline instalation of dependencies

yarn install --offline

Have a safe flight!

Read the original blog entry...

More Stories By Yakov Fain

Yakov Fain is a Java Champion and a co-founder of the IT consultancy Farata Systems and the product company SuranceBay. He wrote a thousand blogs (http://yakovfain.com) and several books about software development. Yakov authored and co-authored such books as "Angular 2 Development with TypeScript", "Java 24-Hour Trainer", and "Enterprise Web Development". His Twitter tag is @yfain

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