Herb: Implement Action View Helper Registry

[marcoroth]

This pull request introduces a comprehensive Action View Helper Registry, a single source of truth for all Rails view helper methods, generated across C, TypeScript, Ruby, Java, and Rust from individual YAML configuration files.

Motivation

Previously, metadata about Action View helpers (signatures, documentation URLs, tag mappings, options) was scattered across multiple hand-written files:

• C handler files (image_tag.c, link_to.c, etc.) with hardcoded detect/extract functions
• A hand-written TypeScript file in the language server (action_view_helpers.ts)
• Hardcoded source strings in linter rules and rewriter code

Adding or modifying a helper required touching 3+ files across multiple languages. There was no central place to answer "what helpers exist?" or "what does this helper produce?"

Additionally, for the precompilation and reactivity it is important to understand which built-in helpers are being used in a template, so that we can either handle it accordingly, or warn/error when we see the usage of one of these helpers in the compilation step for reactive templates.

What changed

Registry data (config/action_view_helpers/)

YAML files organized by gem and module:

config/action_view_helpers/
  actionview/           (187 helpers)
    url_helper/           link_to, button_to, mail_to, ...
    asset_tag_helper/     image_tag, video_tag, ...
    form_tag_helper/      text_field_tag, select_tag, ...
    form_helper/          form_with, text_field, ...
    text_helper/          truncate, highlight, ...
    ...
  actionpack/           (6 helpers)
    polymorphic_routes/   polymorphic_url, polymorphic_path
    ...
  turbo-rails/          (16 helpers)
  actioncable/          (1 helper)
  actiontext/           (3 helpers)

Code generation (templates/template.rb)

New classes (HelperType, HelperTagInfo, HelperContent, HelperSpecialBehavior, etc.) parse the YAML and feed 8 ERB templates that generate:

• C: helper_registry.h/c (type enum, registry struct, lookup functions) + generated_handlers.c/h (detect, extract_tag_name, extract_content functions for all supported helpers)
• TypeScript: action-view-helpers.ts (enum, interfaces, registry maps, scoped query functions)
• Ruby: helper_registry.rb (typed classes, registry module with lookup methods, scoped queries)
• Java: HelperRegistry.java (enum, entry class, static registry)
• Rust: action_view_helpers.rs (enum, structs, lookup functions)

Generated C handlers replace hand-written code

6 of 7 supported helpers now have their detect, extract_tag_name, extract_content, and supports_block functions generated from YAML instead of hand-written. The individual .c files
(image_tag.c, turbo_frame_tag.c, etc.) were stripped down to only their unique helper-specific functions (src extraction, path wrapping, id wrapping). Only link_to.c retains its hand-written transform
due to complex href/route-helper logic.

Language server improvements

• Hover for all helpers: Hovering over any of the registered helpers in ERB shows signature, description, and documentation link, not just the 7 supported ones
• Nested helper hover: Hovering over dom_id inside <%= turbo_frame_tag dom_id(user) do %> shows dom_id's documentation
• Registry-driven lookups: HELPER_BY_SOURCE, HELPERS_BY_TAG_NAME, findPreferredHelperForTag() replace all hardcoded source strings

CleanShot.2026-04-05.at.19.31.21.mp4

Consumer code updates

• Linter: erb-no-javascript-tag-helper, html-require-script-nonce, a11y-no-autofocus-attribute now use registry lookups instead of hardcoded strings
• Rewriter: html-to-action-view-tag-helper uses findPreferredHelperForTag() and HELPER_REGISTRY for tag-to-helper mapping
• Language server: hover_service.ts and rewrite_code_action_service.ts use registry for all helper resolution

Deleted

• javascript/packages/language-server/src/action_view_helpers.ts replaced by generated @herb-tools/core export
• src/analyze/action_view/content_tag.c fully generated
• src/analyze/action_view/tag.c fully generated

[github-advanced-security]

CodeQL found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1611

npx https://pkg.pr.new/@herb-tools/language-server@1611

npx https://pkg.pr.new/@herb-tools/linter@1611

commit: 050f94a

[github-actions]

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