importmap.cr

A Crystal port of the core of importmap-rails 2.2.3 (the Rails 8.1 companion gem) — the JS module pinning DSL plus importmap tag helpers. Namespace Importmap mirrors the original 1:1. Output is byte-identical to the gem (oracle recorded with real importmap-rails 2.2.3 + actionview 8.1.4; the path_to_asset resolver stubbed to /javascripts/<path>, i.e. Rails behavior without sprockets/propshaft).

⚠️ EXPERIMENTAL FRAMEWORK, DO NOT USE IN PRODUCTION YET.

Installation

dependencies:
  importmap_cr:
    github: OrelSokolov/importmap.cr

shards install

Depends on action_view.cr (TagHelper / compute_asset_path, SafeString).

Usage

Importmap.map.draw do |map|
  map.pin "application", preload: true
  map.pin "chart", to: "chart.js"
  map.pin_all_from "app/javascript/controllers", under: "controllers"
end

<%= javascript_importmap_tags %>   <!-- inline importmap + modulepreload + import -->

Integration with railties: helpers are included into ActionController::Base, CRails::Middleware::Static serves /javascripts/* from app/javascript, and crails new generates a layout with javascript_importmap_tags, a config/importmap.cr and app/javascript/application.js.

Feature comparison vs importmap-rails 2.2.3

Feature	Original (importmap-rails)	Port (importmap.cr)	Status
`pin` (`to:`, `preload:` Bool\|String entrypoint)	✅	Same	✅
`pin_all_from` (`under:`, `to:`)	✅	Same; relative `dir` resolved from `Importmap::Map.root` (railties sets it to `CRails.root`)	✅
`draw` DSL	`draw(path)` reads a Ruby config via instance_eval	Block DSL only: `Importmap.map.draw do \|map\| ... end`	🔶
`to_json` (pretty, like Ruby `JSON.pretty_generate`)	✅	Same	✅
`preloaded_module_paths` (+ entry-point filter)	✅	Same, incl. the gem quirk: default `cache_key` ignores `entry_point` changes (helpers pass `cache_key: entry_point`, as the gem does)	✅
`digest` (SHA1), `cache_as` / `clear_cache`	✅	Same	✅
`javascript_importmap_tags`, `javascript_inline_importmap_tag`, `javascript_import_module_tag`, `javascript_importmap_module_preload_tags`, `javascript_module_preload_tag`	✅	Same, byte-identical output	✅
Asset resolution (`path_to_asset` → `compute_asset_path`)	✅ (sprockets/propshaft)	`/javascripts/x.js`, URLs pass through; does not fail on missing files (no manifest)	🔶
SRI integrity (`enable_integrity!`, `integrity:`)	✅	P2 — omitted (no asset pipeline with integrity support)	⬜
Packager (`bin/importmap pin/unpin/update`, jsDelivr/npm)	✅	P2 (needs an HTTP client)	⬜
Reloader (`EventedFileUpdateChecker`)	✅	Not needed (compile-time)	—
CSP nonce in tags	✅	Omitted (no CSP layer; nonce always nil — matches the nil-request oracle)	❌ (equivalent: none, until a CSP layer exists)
`preloaded_module_packages`	✅	Omitted — `preloaded_module_paths` suffices without integrity	❌
Glob quirk: `*/.js{,m}` pins `.js`/`.jsm` but not `.mjs`	✅ (quirk)	Preserved 1:1 (oracle-confirmed)	✅

Testing

crystal spec   # 17 examples, 0 failures; output byte-for-byte

Oracle: oracle/importmap_cases.rb → oracle/importmap_expected.yml (21 cases). Benchmarks: bench/importmap_bench.{cr,rb} against the real gem — ~11.6× faster on tag rendering (bench/results/204-importmap.md).

Repository

importmap.cr

Owner

OrelSokolov

Statistic

0
0
0
1
0
2 days ago
October 12, 2026

License

Links

Synced at

Mon, 12 Oct 2026 05:24:01 GMT

Languages

Crystal 77.06% Ruby 22.94%