Merge branch '289-new-job-yarn-install' into 'latest'

    On Gitlab, this job will be run in the default first stage of your

    pipeline: [`.pre`](https://docs.gitlab.com/ee/ci/yaml/#pre-and-post)

    ⚠️ For this reason, using only this job in your pipeline will not trigger a pipeline in Gitlab.

    You have to add additional jobs.

* Job name: `npm_install`

* Default stage: [`.pre`](https://docs.gitlab.com/ee/ci/yaml/#pre-and-post)

* Docker image: [`node:15.7-buster`](https://hub.docker.com/_/node){:target="_blank"}

## Objective

This job installs `yarn` dependencies listed in your `package.json` and exposes

`node_modules` as cache to other jobs of your pipeline. It allows you to run

`yarn install` only once in your pipeline.

## How to use it

1. Ensure that your project have

   [`package.json`](https://classic.yarnpkg.com/en/docs/package-json/){:target="_blank"}

   file which contains the requirements

2. Add the corresponding URL to your `.gitlab-ci.yml` file (see [Getting

   started](/getting-started)). Example:

    ```yaml

    include:

      - remote: 'https://jobs.r2devops.io/yarn_install.yml'

    ```

3. If you need to customize the job (stage, variables, ...) 👉 check the [jobs

   customization](/use-the-hub/#jobs-customization)

4. Well done, your job is ready to work ! 😀

## Job details

!!! info

    On Gitlab, this job will be run in the default first stage of your

    pipeline: [`.pre`](https://docs.gitlab.com/ee/ci/yaml/#pre-and-post)

    ⚠️ For this reason, using only this job in your pipeline will not trigger a pipeline in Gitlab. 

    You have to add additional jobs.

* Job name: `yarn_install`

* Default stage: [`.pre`](https://docs.gitlab.com/ee/ci/yaml/#pre-and-post)

* Docker image: [`node:15.7-buster`](https://hub.docker.com/_/node){:target="_blank"}

* When: `always`

### Variables

!!! note

    All paths defined in variables are relative and starts from the root of your

    repository.

| Name | Description | Default |

| ---- | ----------- | ------- |

| `PROJECT_ROOT` | Path to the directory containing `package.json`  | `.` |

| `YARN_INSTALL_OPTIONS` | Additional options for `yarn install` | ` ` |

### Cache

This job creates a global cache configuration. Regarding the configuration

applied, cache behavior is the following:

* Shared between all jobs and pipelines on the same branch

* Contains folder `$PROJECT_ROOT/node_modules`

* If `yarn install` produces different result than the cached content

More information on Gitlab caching mechanism in [Gitlab CI/CD caching

documentation](https://docs.gitlab.com/ee/ci/caching/index.html).

name: yarn_install

description: A ready to use `yarn` job that install dependencies and expose `node_modules` as cache to other jobs

default_stage: others

icon: 💡

maintainer: coconux

license: MIT

* Initial version