Upgrade Yarn to v4

Following the deprecation of Yarn 1.xx and 2.xx, we have upgraded Whitehall's base image to use Yarn v4.
Consequently, flags like `--production` `--frozen-lockfile` have been removed.

Associated PR: alphagov/govuk-docker#908

Flags: https://yarnpkg.com/cli/install

JIRA: https://gov-uk.atlassian.net/browse/WHIT-1954

Author: eYinka

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
 
   test-javascript:
     name: Test JavaScript
-    uses: alphagov/govuk-infrastructure/.github/workflows/jasmine.yml@main
+    uses: alphagov/govuk-infrastructure/.github/workflows/jasmine.yml@corepack
     with:
       useWithRails: true
 

.github/workflows/cucumber.yml

@@ -29,7 +29,7 @@ jobs:
           bundler-cache: true
 
       - name: Setup Node
-        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@main
+        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@corepack
 
       - name: Cache Playwright Chromium browser
         id: playwright-cache

.github/workflows/lintjs.yml

@@ -11,7 +11,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Setup Node
-        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@main
+        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@corepack
 
       - name: Run lint:js
         run: yarn run lint:js

.github/workflows/lintprettier.yml

@@ -11,7 +11,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Setup Node
-        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@main
+        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@corepack
 
       - name: Run lint:prettier
         run: yarn run lint:prettier

.github/workflows/lintscss.yml

@@ -11,7 +11,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Setup Node
-        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@main
+        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@corepack
 
       - name: Run lint:scss
         run: yarn run lint:scss

.github/workflows/minitest.yml

@@ -50,7 +50,7 @@ jobs:
           bundler-cache: true
 
       - name: Setup Node
-        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@main
+        uses: alphagov/govuk-infrastructure/.github/actions/setup-node@corepack
 
       - name: Precompile assets
         uses: alphagov/govuk-infrastructure/.github/actions/precompile-rails-assets@main

.gitignore

@@ -28,6 +28,8 @@
 /failures
 /node_modules
 /yarn-error.log
+.yarn/
+.pnp.*
 .cache/
 .DS_Store
 /app/assets/builds/*

.yarnrc.yml

@@ -0,0 +1 @@
+nodeLinker: node-modules

Dockerfile

@@ -10,8 +10,9 @@ ENV JWT_AUTH_SECRET=unused_yet_required
 WORKDIR $APP_HOME
 COPY Gemfile* .ruby-version ./
 RUN bundle install
-COPY package.json yarn.lock ./
-RUN yarn install --production --frozen-lockfile --non-interactive --link-duplicates
+COPY package.json yarn.lock ./ 
+RUN corepack enable
+RUN yarn install --immutable
 COPY . .
 RUN bootsnap precompile --gemfile .
 RUN rails assets:precompile && rm -fr log

package.json

@@ -4,6 +4,7 @@
   "private": true,
   "author": "Government Digital Service",
   "license": "MIT",
+  "packageManager": "[email protected]",
   "scripts": {
     "lint": "yarn run lint:js && yarn run lint:scss && yarn run lint:prettier",
     "lint:js": "eslint --cache --cache-location .cache/eslint --color --ignore-path .gitignore -- \"**/*.js\"",