4.15.0

4.15.0

• Add experimental caching support, opt-in per component via include ViewComponent::ExperimentallyCacheable.

  Components have never participated in Rails' template digests, so a <% cache %> block wrapping render MyComponent.new was never invalidated when the component changed (#234, open since 2020).

  Including the module registers the component with Rails' own ActionView::Digestor, so fragment caches are invalidated when the component's template, Ruby class, sidecar files, superclasses, child components, or rendered partials change. This includes components and partials rendered from inline templates and #call methods. Adding cache_on caches the component's own rendered output, optionally guarded by if:/unless:, and .cache_digest exposes the digest for use outside a request.

  class MessageComponent < ViewComponent::Base
    include ViewComponent::ExperimentallyCacheable
  
    cache_on :message, unless: -> { message.draft? }
  
    def initialize(message:)
      @message = message
    end
  end

  This API is experimental and may change or be removed in a non-major release. It's shipping opt-in and per-component precisely so we can iterate on it in response to real-world use. Please try it and tell us what breaks, what's missing, and what feels wrong in #234. We're especially interested in feedback on: whether cache_on is the right shape for declaring cache keys, how the feature behaves with slots and content blocks, and whether the # Template Dependency: escape hatch is sufficient for dynamic renders. See the caching guide for details and known caveats.

  This work builds directly on prior art from the community. The cache_on API and the case for component-local caching come from #2126 by Reegan Viljoen. The approach of integrating with Rails' digest tree rather than reimplementing it comes from view_component-cache_digest by Godfrey Chan. The invalidation cases it's tested against were contributed by JWShuff and timburgan, drawing on view_component-fragment_caching by Patrick Arnett. The issue was opened and researched by ozzyaaron, pinzonjulian, and Derek Kniffin, and the digest workaround that surfaced the superclass gap came from cannikin and rnestler. Cache-key correctness issues (formats sharing an entry, positional nil collisions, conditional caching, and ignored cache_on blocks) were found and reported by Reegan Viljoen.

  Reegan Viljoen, Godfrey Chan, JWShuff, timburgan, Patrick Arnett, ozzyaaron, pinzonjulian, Derek Kniffin, cannikin, rnestler, Joel Hawksley