action_view.cr

A Crystal port of Rails ActionView 8.1.4 — ERB templates, layouts, partials, the form builder and view helpers. Namespace ActionView mirrors the original 1:1; templates keep ERB syntax and are compiled into render methods at build time (via a run() template processor, like the stdlib's ECR). <%= %> auto-escapes; a SafeString type marks safe HTML. Parity is verified against the real gem with oracle specs (151 examples, 0 failures).

⚠️ EXPERIMENTAL FRAMEWORK, DO NOT USE IN PRODUCTION YET.

Installation

dependencies:
  action_view_cr:
    github: OrelSokolov/action_view.cr

shards install

Requires Crystal >= 1.21.0; pairs with active_support.cr and action_pack.cr (routes/params).

Usage

Templates are Rails-compatible ERB (app/views/<controller>/<action>.html.erb):

<%# app/views/posts/show.html.erb %>
<h1><%= @post.title %></h1>
<%= link_to "Edit", edit_post_path(@post) %>

<%= form_with model: @post do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title %>
  <%= f.submit %>
<% end %>

# The application declares partials and their local types at compile time:
compile_partials({
  "shared/post" => {post: Post},
})

Feature comparison vs actionview 8.1.4

Rendering

Feature	Original (actionview)	Port (action_view.cr)	Status
ERB action templates + layouts (yield, nested layouts)	✅	Compile-time render methods; Rails 8.1 newline semantics (trailing \n chomp on action templates)	✅
content_for / provide / content_for?, capture, concat	✅	Same	✅
render partial: "shared/post", locals: {...}, collection render (render @posts → _post.erb, <name>_counter, <name>_iteration)	✅	Locals are real typed arguments of the compiled method; counter is 0-based (Rails 7.1+ behavior, oracle-confirmed)	🔶
Controller instance variables visible in views	✅	Same	✅

Form helpers

Feature	Original	Port	Status
form_with model: @post do |f| (+ url:, scope:), form_tag + *_tag helpers	✅	Same, incl. CSRF authenticity token in non-GET forms (authenticity_token: false to disable)	✅
form_with model: without url: — action from named routes (polymorphic)	✅	Same: single model → model_path/models_path by persisted?, array [user, post] → nested user_post(s)_path; scope from the LAST model (oracle fw_poly_*). Resolution goes through FormHelper.polymorphic_path, wired to CRails::Routes::UrlHelpers.polymorphic_path by railties_cr at boot	✅
FormBuilder: label, text_field, password_field, hidden_field, text_area, check_box, radio_button, submit, file_field, typed fields (email/number/date/time/datetime/month/week/color/range/search/telephone/url), button, field_id/field_name	✅	Same; models implement the ActionView::FormModel interface (form_scope/form_attributes/form_persisted?/form_model_name); check_box takes checked/unchecked values as named args	✅
form_with without a block (no </form>); multipart enctype from file_field	✅	Same (capture-first form rendering)	✅
FormOptionsHelper: options_for_select (+disabled), options_from_collection_for_select, option_groups_from_collection_for_select, grouped_options_for_select (+prompt)	✅	Same; collections implement FormOption/GroupOption interfaces instead of method-name symbols	✅
FormBuilder: select, collection_select, grouped_collection_select, weekday_select, collection_check_boxes, collection_radio_buttons (include_blank/prompt/selected/disabled/multiple + hidden companions)	✅	Same, byte-exact; checked-values for checkbox collections via checked: arg (no array FormValues)	✅
Tag-level fields: text/password/email/search/url/tel/date/color/number/range + file/time/datetime/datetime_local/month/week/phone (*_tag), image_submit_tag	✅	Same, byte-exact (incl. datetime → datetime-local type, image src /images/ asset prefix)	✅
button_tag/label_tag with block; check_box_tag/radio_button_tag id: nil, disabled, attribute order (opts before checked)	✅	Same (oracle-locked merge order)	✅
fields_for (view-level + FormBuilder#fields_for)	✅	Byte-identical nested names user[posts_attributes][0][title], auto hidden_field :id after the block for persisted children, child_index:/include_id:	✅
fields (form_with's builder, no form tag)	✅	Same, ids follow form_with_generates_ids; model: accepts arrays (scope from the LAST model); url: accepted for parity, ignored (oracle fields_*)	✅
form_for (legacy wrapper)	✅	Same: ids always on, dom class/id from the LAST model (edit_post/edit_post_7/new_post), user html: class replaces dom class, local form (oracle ffor_*)	✅
Nested-attributes index naming (post[comments_attributes][0][_destroy])	✅	Same	✅

Content, tags, text & numbers

Feature	Original	Port	Status
Output safety (html_safe, raw, safe_join, escape_once)	✅	SafeString marker type	✅
content_tag, tag("br"), tag.br dot form	✅	Dot form is a fixed list of ~110 HTML elements, macro-generated	🔶
URL helpers: link_to (options/block), link_to_if/unless, button_to, current_page?, mail_to/phone_to/sms_to	✅	Same	✅
url_for(model) polymorphic URLs	✅	Form-level equivalent: form_with model: resolves the action polymorphically via FormHelper.polymorphic_path (see Form helpers)	🔶
Text: pluralize, truncate, excerpt, highlight, word_wrap, simple_format, cycle/...	✅	Same	✅
Numbers: number_to_currency/delimiter/precision/human_size/human/percentage/phone	✅	Same (locale data)	✅
debug, distance_of_time_in_words, time_ago_in_words, t/l (I18n)	✅	Same	✅
Asset helpers: stylesheet_link_tag, javascript_include_tag, javascript_tag, image_tag, video_tag, audio_tag, favicon_link_tag, csrf_meta_tags, csp_meta_tag	✅	Same; fingerprint manifest public/assets/manifest.json + compute_asset_path (Sprockets/Propshaft are not ported)	🔶
sanitize, strip_tags, strip_links	✅	Needs an HTML parser (lexbor)	⬜
Fragment cache: cache/cache_if/cache_unless/fragment_cache_key	✅	Explicit string keys, ActionView.perform_caching/cache_store (NullStore by default)	🔶
Russian-doll cache keys (template digest, dependency tracker), array/object keys	✅	Not ported	⬜

Vite integration (beyond actionview — ports vite_rails 3.0.19 / vite_ruby 3.9.2)

Feature	Original (vite_rails)	Port	Status
vite_javascript_tag (ESM + modulepreload + CSS chunks), vite_stylesheet_tag, vite_asset_path, vite_image_tag	✅	Byte-identical output vs oracle; vite 5/6 manifest format	✅
Dev-server detection & dev tags (vite_client_tag, vite_react_refresh_tag)	✅	TCP probe (1 s cache), dev lookup without manifest; HTTP/ws proxy lives in railties	🔶
config/vite.json, custom tag options, skip_proxy/auto_build	✅	Not supported; type: is a String, not a Symbol	❌ (equivalent: class-level ViteRuby::Manifest properties + env vars)

Deviations & Crystal-specific notes

• Locals are a Crystal literal: locals: {"post" => post} (a Ruby-style {post: post} is a NamedTuple in Crystal).
• Partial local types are declared by the application in compile_partials (compile-time framework; Crystal does not allow Object in generics).
• FormBuilder methods are a fixed set (in Rails they are also generated once by a CodeGenerator).
• form_with model: [a, b] needs an explicit element type — [room, message] of ActionView::FormModel — Crystal array literals of mixed model classes do not widen to the module interface.
• Templates are scanned and compiled at build time (CRAILS_VIEWS or app/views).

Testing

crystal spec

Oracle specs: oracle/cases.rb recorded against actionview 8.1.4 → oracle/expected.yml; the Vite layer is recorded against real vite_rails 3.0.19 / vite_ruby 3.9.2 (oracle/vite_cases.rb, oracle/vite_dev_cases.rb). Suite: 151 examples, 0 failures.