Initial scaffold: gemspec, lib, tests, CI matrix, scripts, and docs

Author: dbongo

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+jobs:
+  test:
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # ---- Ruby ≤ 2.2 need Bundler 1.17.x ------------------------
+          - ruby: "2.0.0-p648"
+            bundler: "1.17.3"
+          - ruby: "2.1.10"
+            bundler: "1.17.3"
+          - ruby: "2.2.10"
+            bundler: "1.17.3"
+          # ---- Normal modern combo -----------------------------------
+          - ruby: "2.3.8"
+          - ruby: "2.4.10"
+          - ruby: "2.5.9"
+          - ruby: "2.6.7"
+          - ruby: "2.7.8"
+          - ruby: "3.0.6"
+          - ruby: "3.1.4"
+          - ruby: "3.2.3"
+          - ruby: "3.3.0"
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler: ${{ matrix.bundler || 'latest' }}
+          bundler-cache: true   # caches Gem/ bundler dir
+
+      # For 2.0–2.2, force-install bundler 1.17 (setup-ruby can’t)
+      - name: Install Bundler 1.x on very old Rubies
+        if: matrix.bundler
+        run: gem install bundler -v "$BUNDLER_VERSION"
+        env:
+          BUNDLER_VERSION: ${{ matrix.bundler }}
+
+      - name: Install dependencies
+        run: bundle install --jobs 3 --retry 3
+
+      - name: Run specs
+        run: bundle exec rspec

.gitignore

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+# macOS
+.DS_Store
+
+# editor
+*.swp
+.idea/
+.vscode/
+
+# ruby
+.ruby-version
+.rvmrc
+/.bundle/
+/vendor/bundle/
+/Gemfile.lock
+
+# gems and packages
+*.gem
+/pkg/
+
+# docs and coverage
+/doc/
+/rdoc/
+/_yardoc/
+/.yardoc
+/coverage/
+/spec/reports/
+
+# logs and temp
+/log/
+/tmp/
+
+# test
+.rspec_status
+
+# misc
+tags
+.loadpath
+.project

.rspec

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+--format documentation
+--color
+--require spec_helper

Gemfile

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+source "https://rubygems.org"
+
+git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
+
+# Specify your gem's dependencies in callable.gemspec
+gemspec

LICENSE.txt

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+The MIT License (MIT)
+
+Copyright (c) 2025 Michael Crowther
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# Callable
+
+Callable is a minimal Ruby mix-in that provides your classes with a simple `.call` class method. It allows you to instantiate and immediately invoke an instance method (`call`) without boilerplate or additional dependencies. Perfect for clean, readable, and concise service objects.
+
+## Features
+
+- Provides a `.call` class method to any Ruby class.
+- Transparently forwards positional arguments, keyword arguments, and blocks.
+- Handles argument errors gracefully, raising clear exceptions.
+- Zero external runtime dependencies.
+- Compatible with MRI Ruby 2.0 through Ruby 3.x.
+
+## Installation
+
+Add this to your application's Gemfile:
+
+```ruby
+gem 'callable'
+```
+
+Then execute:
+
+```bash
+bundle install
+```
+
+Or install directly:
+
+```bash
+gem install callable
+```
+
+## Usage
+
+Simply include Callable in your class and implement an instance method named `call`:
+
+```ruby
+class SendNotification
+  include Callable
+
+  def initialize(user, message)
+    @user = user
+    @message = message
+  end
+
+  def call
+    NotificationMailer.notify(@user, @message).deliver_now
+  end
+end
+
+SendNotification.call(current_user, "Hello from Callable!")
+```
+
+Then run your class using the `.call` class method:
+
+```ruby
+SendNotification.call(current_user, "Hello from Callable!")
+
+# or use .() (syntactic sugar for .call)
+SendNotification.(current_user, "Hello from Callable!")
+```
+
+
+## Development
+
+After cloning the repo, install dependencies with `bundle install`, then run tests with `bundle exec rspec`.
+
+## Contributing
+
+Bug reports and pull requests are welcome on GitHub at https://github.com/dbongo/callable.
+
+## License
+
+The gem is available under the MIT License.

Rakefile

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+require "bundler/gem_tasks"
+require "rspec/core/rake_task"
+
+desc "Run specs"
+RSpec::Core::RakeTask.new(:spec)
+
+# Run the suite under every ruby installed via rbenv/rvm
+namespace :multi do
+  task :spec do
+    rubies = %w[
+      2.0.0-p648 2.1.10 2.2.10 2.3.8 2.4.10 2.5.9
+      2.6.7 2.7.8 3.0.6 3.1.4 3.2.3 3.3.0
+    ]
+    rubies.each do |v|
+      puts "\n=== Ruby #{v} ==="
+      cmd = "RBENV_VERSION=#{v} bundle _#{v < '2.3' ? '1.17.3' : '2'}_ exec rspec"
+      system(cmd) || abort("Failed on #{v}")
+    end
+  end
+end

bin/console

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+#!/usr/bin/env ruby
+
+require "bundler/setup"
+require "callable"
+
+# You can add fixtures and/or initialization code here to make experimenting
+# with your gem easier. You can also use a different console, if you like.
+
+# (If you use this, don't forget to add pry to your Gemfile!)
+# require "pry"
+# Pry.start
+
+require "irb"
+IRB.start(__FILE__)

bin/setup

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+#!/usr/bin/env bash
+set -euo pipefail
+IFS=$'\n\t'
+set -vx
+
+bundle install
+
+# Do any other automated setup that you need to do here

callable.gemspec

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+# frozen_string_literal: true
+
+require_relative "lib/callable/version"
+
+Gem::Specification.new do |spec|
+  spec.name          = "callable"
+  spec.version       = Callable::VERSION
+  spec.authors       = ["Michael Crowther"]
+  spec.email         = ["[email protected]"]
+
+  spec.summary       = "Lightweight .call mix-in for service objects"
+  spec.description   = "Callable provides Ruby classes with a convenient `.call` method, "\
+                       "simplifying instantiation and method invocation."
+  spec.homepage      = "https://github.com/dbongo/callable"
+  spec.license       = "MIT"
+  spec.required_ruby_version = ">= 2.0.0"
+
+  spec.metadata = {
+    "homepage_uri"    => spec.homepage,
+    "source_code_uri" => spec.homepage,
+    "changelog_uri"   => "#{spec.homepage}/blob/main/CHANGELOG.md"
+  }
+
+  spec.files         = Dir["lib/**/*.rb", "LICENSE", "README.md"]
+  spec.require_paths = ["lib"]
+
+  spec.add_development_dependency "bundler", ">= 1.17"
+  spec.add_development_dependency "rake", "~> 13.0"
+  spec.add_development_dependency "rspec", "~> 3.0"
+end