Validate NPM package scope

This commit updates our NPM .gitlab-ci.yml template to include a step
that validates that the package is correctly scoped to the project's
root namespace.

This commit also makes a number of other smaller improvements
to the template.

changelogs/unreleased/nfriend-validate-package-name.yml

+---
+title: Add package scope validation to Node.js template
+merge_request: 34778
+author:
+type: added

lib/gitlab/ci/templates/npm.gitlab-ci.yml

-image: node:latest
+default:
+  image: node:latest
 
+  # Validate that the repository contains a package.json and extract a few values from it.
+  before_script:
+    - |
+      if [[ ! -f package.json ]]; then
+        echo "No package.json found! A package.json file is required to publish a package to GitLab's NPM registry."
+        echo 'For more information, see https://docs.gitlab.com/ee/user/packages/npm_registry/#creating-a-project'
+        exit 1
+      fi
+    - NPM_PACKAGE_NAME=$(node -p "require('./package.json').name")
+    - NPM_PACKAGE_VERSION=$(node -p "require('./package.json').version")
+
+# Validate that the package name is properly scoped to the project's root namespace.
+# For more information, see https://docs.gitlab.com/ee/user/packages/npm_registry/#package-naming-convention
+validate_package_scope:
+  stage: build
+  script:
+    - |
+      if [[ ! $NPM_PACKAGE_NAME =~ ^@$CI_PROJECT_ROOT_NAMESPACE/ ]]; then
+        echo "Invalid package scope! Packages must be scoped in the root namespace of the project, e.g. \"@${CI_PROJECT_ROOT_NAMESPACE}/${CI_PROJECT_NAME}\""
+        echo 'For more information, see https://docs.gitlab.com/ee/user/packages/npm_registry/#package-naming-convention'
+        exit 1
+      fi
+
+# If no .npmrc if included in the repo, generate a temporary one to use during the publish step
+# that is configured to publish to GitLab's NPM registry
 create_npmrc:
   stage: build
   script:
     - |
-      if [ ! -f .npmrc ]; then
+      if [[ ! -f .npmrc ]]; then
         echo 'No .npmrc found! Creating one now. Please review the following link for more information: https://docs.gitlab.com/ee/user/packages/npm_registry/index.html#authenticating-with-a-ci-job-token'
 
-        echo "@${CI_PROJECT_NAMESPACE%%/*}:registry=\${CI_SERVER_URL}/api/v4/projects/${CI_PROJECT_ID}/packages/npm/" >> .npmrc
-        echo '//gitlab.com/api/v4/packages/npm/:_authToken=${CI_JOB_TOKEN}' >> .npmrc
-        echo '//gitlab.com/api/v4/projects/${CI_PROJECT_ID}/packages/npm/:_authToken=${CI_JOB_TOKEN}' >> .npmrc
+        {
+          echo "@${CI_PROJECT_ROOT_NAMESPACE}:registry=\${CI_SERVER_URL}/api/v4/projects/${CI_PROJECT_ID}/packages/npm/"
+          echo '//gitlab.com/api/v4/packages/npm/:_authToken=${CI_JOB_TOKEN}'
+          echo '//gitlab.com/api/v4/projects/${CI_PROJECT_ID}/packages/npm/:_authToken=${CI_JOB_TOKEN}'
+        } >> .npmrc
+
       fi
   artifacts:
     paths:
       - .npmrc
 
+# Publish the package. If the version in package.json has not yet been published, it will be
+# published to GitLab's NPM registry. If the version already exists, the publish command
+# will fail and the existing package will not be updated.
 publish_package:
   stage: deploy
   script:
-    - export NPM_PACKAGE_NAME=$(node -p "require('./package.json').name")
-    - export NPM_PACKAGE_VERSION=$(node -p "require('./package.json').version")
     - |
       {
         npm publish &&
-        echo "Successfully published version $NPM_PACKAGE_VERSION of $NPM_PACKAGE_NAME to GitLab's NPM registry."
+        echo "Successfully published version ${NPM_PACKAGE_VERSION} of ${NPM_PACKAGE_NAME} to GitLab's NPM registry: ${CI_PROJECT_URL}/-/packages"
       } || {
-        echo "No new version of $NPM_PACKAGE_NAME published. This is most likely because version $NPM_PACKAGE_VERSION already exists in GitLab's NPM registry."
+        echo "No new version of ${NPM_PACKAGE_NAME} published. This is most likely because version ${NPM_PACKAGE_VERSION} already exists in GitLab's NPM registry."
       }