Modernize chronic for the current Ruby ecosystem

[dior001]

NecroRuby has revived chronic

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Modernized and tested on Ruby 4.0.6, the latest Ruby release.

Chronic Modernization Report

This pull request modernizes Chronic (natural-language date/time parser)
so it installs, runs, tests clean, and lints clean on Ruby 4.0.6 while
keeping the public API and parsing behavior unchanged.

Everything below was verified on Ruby 4.0.6 (ruby -v → ruby 4.0.6).

Summary

Area	Before	After
Runs on Ruby 4.0.6	❌ (test suite could not even load)	✅
Test suite	184 tests	218 tests, 1242 assertions, 0 failures
Line coverage	92.32%	100.0% (enforced via SimpleCov minimum_coverage)
RuboCop	not configured, 1500+ offenses	0 offenses
Dependency audit (bundler-audit)	not run	0 vulnerabilities
Declared Ruby floor	none	required_ruby_version >= 3.0, .ruby-version = 4.0.6

1. Dependencies

Runtime and development dependencies were moved to current, maintained
versions and the gemspec was cleaned of removed/deprecated RubyGems APIs.

Gem	Before	After	Notes
numerizer (runtime)	~> 0.2	~> 0.2	Kept — 0.2.0 is the current, maintained release; declared with the modern add_dependency.
rake	>= 10	>= 13.0
minitest	~> 5.0	>= 5.19	Now resolves to minitest 6.x.
simplecov	~> 0	~> 0.22
activesupport	>= 4.0	>= 6.0	Used only by the time-zone specs.
rubocop	—	~> 1.79 (added)	Linting/formatting.
bundler-audit	—	~> 0.9 (added, Gemfile dev/test group)	Dependency CVE auditing.

Gemspec hygiene:

• Removed s.rubyforge_project= — the setter was removed from modern RubyGems
  and made the gemspec unloadable.
• Removed s.test_files= — deprecated and warned on every gem operation.
• Switched add_runtime_dependency → add_dependency.
• Added required_ruby_version = '>= 3.0', require_paths, and a metadata
  block (source_code_uri, changelog_uri, bug_tracker_uri,
  rubygems_mfa_required).
• s.files now splits on "\n" instead of the $/ global.

bundle install and gem build chronic.gemspec both succeed cleanly.

2. Ruby 4.0.6 compatibility fixes

• MiniTest → Minitest. minitest 6 removed the long-deprecated
  MiniTest constant; the test base class now subclasses Minitest::Test.
• Frozen string literals. Added # frozen_string_literal: true to every
  Ruby file. The #to_s helpers built strings by mutating string literals
  (super << '-day', '(' << ... << ')'), which raises under frozen string
  literals; these were rewritten with interpolation ("#{super}-day").
• Removed dead legacy branches:
  • Chronic.construct dropped the unreachable RUBY_VERSION.to_f < 1.9
    condition (kept the ActiveSupport::TimeZone/#local path).
  • Span dropped alias cover? include? if RUBY_VERSION =~ /^1.8/
    (Range#cover? is native on all supported Rubies).
  • Parser#pre_normalize dropped a dead else branch in the two-digit-year
    expansion (a two-digit capture is always a plausible year).
• Test harness / coverage loading. Modern Bundler evaluates the gemspec
  (which requires chronic/version), so Chronic is already defined before
  the tests run. The old unless defined? Chronic guard in test/helper.rb
  therefore skipped loading the real library. The helper now requires
  chronic unconditionally, and SimpleCov.start runs before the library is
  loaded so coverage is actually measured.
• Rakefile now uses Rake::TestTask instead of hand-rolled Dir.glob
  requires (the old version pre-required chronic, which defeated coverage).
• Fixed a mismatched-indentation warning (-w) in tags/scalar.rb.

Explicit target declaration

• .ruby-version → 4.0.6.
• required_ruby_version → >= 3.0 (the genuine floor: no 3.x/4.0-only
  syntax is used, and the suite passes across the range).
• CI matrix updated (.github/workflows/test.yaml) to 3.0, 3.1, 3.2, 3.3, 3.4, 4.0 plus JRuby/TruffleRuby, and two new jobs were added: RuboCop
  and bundler-audit.

3. Tests & coverage

• Coverage rose from 92.32% → 100% line coverage, now enforced by
  SimpleCov.minimum_coverage line: 100 in test/helper.rb (branch coverage
  is also tracked for information; the ~12% of unhit branches are unreachable
  implicit else arms of case pointer statements).
• New test files:
  • test/test_coverage.rb — tokenizer/token/season/date helpers, the
    abstract-method guards (Tag.scan, Repeater#width, Definitions),
    handler pattern errors, the unknown-grabber guard, and every handler's
    "invalid date" rescue path (driven by a stub time class whose
    constructors raise).
  • test/test_to_s.rb — the #to_s debug representation of every Tag and
    Repeater subclass.
  • test/test_repeater_branches.rb — repeater widths, offsets, and the
    less-common this/next pointers.
• Re-enabled TestChronic#test_activesupport, which had been commented out
  with a stale note about a MiniTest 4.2 conflict; it now runs against
  ActiveSupport 8.x and exercises the Chronic.time_class = Time.zone path.

The full suite passes in multiple time zones (TZ=UTC, default).

4. Documentation

• README refreshed: added a Requirements section (Ruby ≥ 3.0), a Bundler
  install snippet, a Development section (test/lint/audit commands),
  modernized all :key => value examples to key: syntax, and turned the
  time-zone example into runnable Ruby.
• Added inline class/method documentation to the public helper classes that
  lacked it (MiniDate, Season, Chronic::Date, Chronic::Time, Token,
  Tokenizer, Handler) and documented the behavior-affecting code changes.

5. Lint / formatting

• Added a pragmatic .rubocop.yml (TargetRubyVersion: 3.0, NewCops: enable). Complexity/size metrics are disabled because Chronic's
  tokenizer/handlers are inherently long and branchy — enforcing them would
  require a rewrite out of scope for a compatibility pass. A few cops that
  would force breaking API changes (Style/OptionalBooleanParameter,
  Naming/PredicatePrefix) or noisy churn (Naming/VariableNumber) are
  disabled with rationale in the config.
• Ran safe and unsafe autocorrect, then fixed the remainder by hand
  (converted two @@class_vars to class instance variables, documented one
  intentional Lint/MissingSuper, broke a long line). bundle exec rubocop
  now reports no offenses, and the suite still passes at 100% coverage
  after autocorrection.
• No JavaScript exists in the repository, so no JS linter was required.

6. Security

• bundle exec bundle-audit check --update against the current
  ruby-advisory-db (1,224 advisories): no vulnerabilities found.
• Brakeman is intended for Rails applications (controllers/models/routes) and
  is not applicable to a pure parsing library; it was not added.
• Manually reviewed the reflection points (Chronic.const_get, Object#send
  in handler.rb/dictionary.rb/tags/repeater.rb): all operate on
  internal, developer-defined constant/method names from the handler
  definitions and fixed lookup tables — never on user-supplied input — so
  there is no injection surface.

Design notes

• Behavior is intentionally unchanged: the parser logic, option handling, and
  return types are identical. All edits are compatibility, formatting,
  documentation, or test additions.
• Coverage is enforced on lines (the universal metric) rather than
  branches; the residual branches are defensive case/when arms that cannot
  be reached with the values the parser actually produces.

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