active_support.cr

A Crystal port of Rails ActiveSupport 8.1.4 — core extensions (blank?, Duration, date math, Inflector, deep hash ops), Concern, delegate, Notifications, cache stores, I18n, number helpers, message verification/encryption and time zones. Namespace ActiveSupport mirrors the original 1:1; the goal is that Ruby snippets from the Rails docs work unchanged. Estimated parity ~85%. Core extensions are implemented by reopening Crystal stdlib types (adding methods is allowed; overriding existing ones is not) and by macros in place of define_method.

⚠️ EXPERIMENTAL FRAMEWORK, DO NOT USE IN PRODUCTION YET.

Installation

dependencies:
  active_support_cr:
    github: OrelSokolov/active_support.cr

shards install

Requires Crystal >= 1.21.0. pg and redis are needed only for the optional adapters/* cache stores.

Usage

require "active_support_cr"

2.days.ago
%w[a b c].to_sentence            # => "a, b, and c"
"post".pluralize                  # => "posts"
hash.deep_merge(other)
"42".present?                     # => true
Time.use_zone("Europe/Berlin") { Time.current }

Ruby-compat aliases

Ruby's attr_* macros live in the zero-dependency attr_reader.cr shard and are re-exported here (delegating to the idiomatic Crystal getter/setter/property):

class Entry
  attr_reader :body, :content_type        # Ruby symbol style
  attr_accessor hits : Int32 = 0          # typed declarations work too
end

Feature comparison vs activesupport 8.1.4

Core extensions

Feature	Original (activesupport)	Port (active_support.cr)	Status
Object: blank?, present?, presence, in?, presence_in, deep_dup, to_param	✅	Same	✅
NilClass: blank?, present?, try	✅	Same	✅
String: squish, truncate, truncate_bytes, at/from/to, first/last, starts_with?/ends_with?, exclude?, remove, indent, strip_heredoc	✅	Same	✅
Inflector: pluralize, camelize, underscore, tableize, classify, humanize, titleize, parameterize, demodulize, foreign_key, ordinalize	✅	Same	✅
Hash: symbolize_keys, deep_symbolize_keys, stringify_keys, except, slice, reverse_merge, with_defaults, deep_merge, deep_transform_keys/values, compact_blank, assert_valid_keys	✅	Same	✅
Array: in_groups_of, in_groups, split, extract!, to_sentence, second..fifth, second_to_last, wrap, excluding, including	✅	Same	✅
Enumerable: index_by, index_with, many?, exclude?, pluck, pick, sole, in_order_of, compact_blank	✅	Same	✅
Int/Numeric: seconds..years, bytes..exabytes, multiple_of?, in_milliseconds (Duration mechanics)	✅	Duration is a fixed Time::Span (see deviations)	🔶
Date/Time math: beginning/end_of_*, all_day/..., ago/since, advance, change, yesterday/tomorrow, next_week/prev_*, months_ago/..., next_occurring, past?/future?/today?, to_fs(:db/:short/:long/:iso8601)	✅	Same	✅
constantize / String#constantize	✅	Not portable — dependent shards use compile-time registries	❌ (equivalent: compile-time class registry)

Time zones

Feature	Original	Port	Status
Time.zone, TimeWithZone, in_time_zone, utc/localtime, formatted_offset	✅	TimeZone built on Time::Location; TWZ arithmetic, <=>/== by UTC instant, zoned strftime, to_fs	✅
Per-user timezone: Time.use_zone(zone, &)	✅	Fiber-local override registry + ensure-restore	✅
Time.current, TimeZone#now, I18n.l with TWZ	✅	Same	✅
DST-aware calendar Duration arithmetic across TWZ	✅	Duration is a fixed span — twz + 1.day always shifts 24 h	❌ (equivalent: shift via Time#shift calendar math)

Infrastructure

Feature	Original	Port	Status
ActiveSupport::Concern (included do / class_methods do)	✅	Crystal included hook + macros	✅
attr_reader / attr_writer / attr_accessor	✅	Re-exported from the attr_reader.cr shard; Ruby symbol args (:foo) and typed declarations accepted	✅
delegate :x, to: :y, prefix:, allow_nil: / delegate_missing_to	✅	Macros	✅
mattr_accessor/cattr_accessor, class_attribute, thread_mattr_*	✅	Macros over @@/fiber-locals	✅
ActiveSupport::Notifications (instrument/subscribe/publish)	✅	Same	✅
ActiveSupport::Cache: MemoryStore, NullStore, FileStore; fetch/read/write/exist?/delete, expires_in:, race_condition_ttl:	✅	Same Store API	✅
RedisCacheStore	✅	adapters/redis_cache.cr (SET/GET EX, INCRBY counters, namespace); stores raw strings — INCR on a write-stored integer succeeds (Rails wraps values in a coder and returns nil)	🔶
SolidCache (PG table)	separate gem	adapters/pg_cache.cr: solid_cache_entries(key, value, expires_at) + atomic SQL counters + delete_expired	🔶
I18n: t(key, scope:, default:, count:), yml locales, pluralization, l, available_locales, fallbacks	✅	Same	✅
NumberHelper family	✅	Same (locale data)	✅
MessageVerifier / MessageEncryptor (signed/encrypted cookies)	✅	SHA1/SHA256 digests, KeyGenerator-derived keys, legacy {"_rails":...} envelope read/write (wire format of actionpack 8.1 cookies)	✅
SecureRandom.base58/base36, Digest::UUID	✅	Same	✅
ActiveSupport::CurrentAttributes	✅	class Current < AS::CurrentAttributes, typed attribute user: User? (nilable), class-level accessors, reset/reset_all; reset wired into request dispatch by railties.cr	🔶 (process-global class vars, not fiber-isolated; no instance/set{}/callbacks API)
TaggedLogging, Deprecation, BacktraceCleaner	✅	Same	✅
HashWithIndifferentAccess	✅	Approximation used by params: Symbol|String keys	🔶

Deviations & Crystal-specific notes

• Core extensions reopen stdlib types (struct Int, class String); overriding existing stdlib methods is forbidden, so those keep Crystal semantics.
• Duration is a fixed Time::Span: calendar months/years have variable length, and TWZ arithmetic does not cross DST boundaries the way Rails durations do.
• The fiber-local zone registry is not cleaned up if a fiber dies inside a use_zone block; Time.zone without a fiber override is process-global (like Rails' Time.zone=).
• FileStore writes timestamps with sub-second precision (expiry < 1 s).
• Cache stores keep raw string values (see RedisCacheStore row).

Testing

crystal spec

Suite: 323/323. Oracle specs (oracle/cases.rb → expected.yml, including 19 tz_* timezone cases) are recorded with the real activesupport 8.1.4 and replayed unchanged; cache stores are additionally verified against a real redis-server (oracle/cache_stores_cases.rb) and a shared contract spec runs across all four stores.