Plan 03: Dropdown Stabilization & JavaScript Cleanup

Objective

Simplify the dropdown controller by removing the fragile stimulus-use async loading path (V6), improve dropdown state isolation (V7), and clean up global window namespace pollution (V13). This improves JavaScript maintainability and prevents memory leaks in SPA-like Turbo Drive navigation.

Context

• @.claude/skills/hotwire-patterns/SKILL.md -- Stimulus controller patterns and best practices
• @.claude/skills/tdd-cycle/SKILL.md -- TDD workflow for verification
• app/assets/javascripts/source_monitor/controllers/dropdown_controller.js (110 lines) -- fragile async loading with stimulus-use fallback (V6), shared state between instances (V7)
• app/assets/javascripts/source_monitor/controllers/notification_controller.js (63 lines) -- registers on window.SourceMonitorControllers (V13)
• app/assets/javascripts/source_monitor/application.js -- exports window.SourceMonitorStimulus (V13)
• app/views/source_monitor/sources/_row.html.erb -- dropdown for row actions (lines 109-141)
• app/views/source_monitor/sources/_health_status_badge.html.erb -- dropdown for health menu (lines 8-37)
• Code comment on dropdown line 35: "Evaluated for simplification in Phase 20.05.07 - Decision: Keep current implementation." -- This phase overrides that decision with Option A (CSS class toggle only).

Tasks

Task 1: Simplify dropdown_controller.js to CSS class toggle only

Rewrite app/assets/javascripts/source_monitor/controllers/dropdown_controller.js:

• Remove loadTransitions() async method entirely
• Remove transitionModuleValue, hiddenClassValue value definitions (keep hiddenClassValue as simple string default "hidden")
• Remove transitionEnabled, toggleTransition, leave state tracking
• Remove logFallback(), _fallbackLogged flag
• Keep only: toggle() toggles this.menuTarget.classList.toggle(this.hiddenClassValue), hide(event) adds hidden class if click is outside controller element
• hide(event) must check !this.element.contains(event.target) to scope to own controller instance (V7 fix)
• connect() and disconnect() manage click-outside listener on document (not window) for proper cleanup
• Target: ~40 lines

Task 2: Clean up notification_controller.js globals

Modify app/assets/javascripts/source_monitor/controllers/notification_controller.js:

• Remove window.SourceMonitorControllers = window.SourceMonitorControllers || {} and window.SourceMonitorControllers.notification = this
• If other code relies on global access to notification controller, replace with Stimulus dispatch events pattern:
  • Controller dispatches notification:show custom event on this.element
  • Callers use this.dispatch("show", { detail: { message: "..." } }) pattern
• Check if any JS files reference window.SourceMonitorControllers -- if so, update those references

Task 3: Clean up application.js globals

Modify app/assets/javascripts/source_monitor/application.js:

• Remove or guard window.SourceMonitorStimulus = application with environment check
• Option: wrap in if (process.env.NODE_ENV !== "production") or simply remove it (the Stimulus application is accessible via Application.start() return value if needed for debugging)
• Keep window.Turbo.StreamActions.redirect as-is (standard Turbo extension pattern, acceptable)

Task 4: Update dropdown HTML for state isolation

Modify app/views/source_monitor/sources/_row.html.erb:

• Change click@window->dropdown#hide to click@document->dropdown#hide (if keeping declarative) OR rely on the new connect() listener in the controller
• Add data-testid="source-actions-<%= dom_id(source) %>" to each dropdown container for testing

Modify app/views/source_monitor/sources/_health_status_badge.html.erb:

• Same changes: ensure dropdown hide is scoped, add unique data-testid

Task 5: Verify

• yarn build -- succeeds with no ESLint errors
• Rebuild JS assets: check app/assets/builds/source_monitor/application.js is updated
• bin/rails test -- full suite passes (no system test regressions)
• Verify no remaining window.SourceMonitorControllers references: grep -r "SourceMonitorControllers" app/assets/
• Verify no remaining stimulus-use references: grep -r "stimulus-use\|useTransition\|transitionModule" app/assets/