Add erblint to lint ERB and run Rubocop on Ruby embedded in ERB (#492)

Closes #489

README.md

@@ -76,6 +76,8 @@ Where possible we stick to Rails defaults.
   - Install [Overcommit](https://github.com/sds/overcommit) for managing custom
     git hooks. Configure it with our default settings:
     [overcommit.yml](./overcommit.yml)
+  - Use [erb_lint](https://github.com/Shopify/erb-lint) to lint HTML in ERB and
+    run Rubocop on Ruby snippets within ERB
 - General testing
   - RSpec for tests
   - Install [webdrivers](https://github.com/titusfortner/webdrivers)

template.rb

@@ -186,6 +186,13 @@ def apply_template! # rubocop:disable Metrics/MethodLength, Metrics/AbcSize, Met
     # generate routes and models
     apply "variants/code-annotation/template.rb"
 
+    # erblint does not like some of Rails auto-generated ERB code e.g.
+    # `app/views/layouts/mailer.html.erb` so we auto-correct it.
+    copy_file "variants/backend-base/.erb-lint.yml", ".erb-lint.yml"
+    run_with_clean_bundler_env "bundle exec erblint --autocorrect ."
+    git add: "-A ."
+    git commit: "-n -m 'Set up erblint'"
+
     # Run the README template at the end because it introspects the app to
     # discover rake tasks etc.
     apply_readme_template

variants/backend-base/.erb-lint.yml

@@ -0,0 +1,42 @@
+---
+exclude:
+  - '**/vendor/**/*'
+  - '**/node_modules/**/*'
+EnableDefaultLinters: true
+linters:
+  RequireScriptNonce:
+    enabled: true
+  PartialInstanceVariable:
+    enabled: true
+  HardCodedString:
+    enabled: false
+  ErbSafety:
+    enabled: true
+  SpaceInHtmlTag:
+    enabled: false
+  NoJavascriptTagHelper:
+    enabled: false
+  Rubocop:
+    enabled: true
+    rubocop_config:
+      inherit_from:
+        - .rubocop.yml
+      Layout/InitialIndentation:
+        Enabled: false
+      Layout/LineLength:
+        Enabled: false
+      Layout/TrailingEmptyLines:
+        Enabled: false
+      Layout/TrailingWhitespace:
+        Enabled: false
+      Naming/FileName:
+        Enabled: false
+      Style/FrozenStringLiteralComment:
+        Enabled: false
+      Lint/UselessAssignment:
+        Enabled: false
+      Layout/LeadingEmptyLines:
+        Enabled: false
+      Rails/OutputSafety:
+        # Disable this because erb-lint already checks this
+        Enabled: false

variants/backend-base/Gemfile.tt

@@ -60,6 +60,9 @@ group :development, :test do
   gem "factory_bot_rails"
   gem "pry-rails"
   gem "pry-byebug"
+
+  # ERB linting. Run via `bundle exec erblint .`
+  gem "erb_lint", require: false
 end
 
 group :test do

variants/github_actions_ci/workflows/ci.yml.tt

@@ -99,6 +99,8 @@ jobs:
       - name: Check Ruby controller annotations
         run: bundle exec chusaku --exit-with-error-on-annotation
       - run: bundle exec rubocop
+      - name: Run erb-lint to check HTML formatting and run Rubocop on Ruby within ERB
+        run: bundle exec erblint .
       - run: bundle exec brakeman --run-all-checks --exit-on-warn --format plain .
       - run: bundle exec rails db:setup
       - uses: actions/setup-node@v3