From 4718a0cb163d43d9dea4a349b9a59750686c8301 Mon Sep 17 00:00:00 2001
From: seenmyfate <seenmyfate@gmail.com>
Date: Fri, 2 Aug 2013 18:04:16 +0100
Subject: [PATCH] Implement `lock` feature

Ensure a Capistrano version by including a `lock` directive in your
Capfile:

  lock '~> 3.0.0'

An error will be raised if the loaded version of Capistrano does not
meet the dependency specified.
---
 lib/capistrano.rb                             |   1 +
 lib/capistrano/dsl.rb                         |   4 +
 lib/capistrano/version_validator.rb           |  37 +++++++
 spec/lib/capistrano/version_validator_spec.rb | 103 ++++++++++++++++++
 4 files changed, 145 insertions(+)
 create mode 100644 lib/capistrano/version_validator.rb
 create mode 100644 spec/lib/capistrano/version_validator_spec.rb

diff --git a/lib/capistrano.rb b/lib/capistrano.rb
index 51267861..03f873c0 100644
--- a/lib/capistrano.rb
+++ b/lib/capistrano.rb
@@ -4,6 +4,7 @@ require 'sshkit'
 Rake.application.options.trace = true
 
 require 'capistrano/version'
+require 'capistrano/version_validator'
 require 'capistrano/i18n'
 require 'capistrano/dsl'
 require 'capistrano/application'
diff --git a/lib/capistrano/dsl.rb b/lib/capistrano/dsl.rb
index 9765754e..df80e1e8 100644
--- a/lib/capistrano/dsl.rb
+++ b/lib/capistrano/dsl.rb
@@ -39,6 +39,10 @@ module Capistrano
       `whoami`
     end
 
+    def lock(locked_version)
+      VersionValidator.new(locked_version).verify
+    end
+
   end
 end
 self.extend Capistrano::DSL
diff --git a/lib/capistrano/version_validator.rb b/lib/capistrano/version_validator.rb
new file mode 100644
index 00000000..ff610399
--- /dev/null
+++ b/lib/capistrano/version_validator.rb
@@ -0,0 +1,37 @@
+module Capistrano
+  class VersionValidator
+
+    def initialize(version)
+      @version = version
+    end
+
+    def verify
+      if match?
+        self
+      else
+        fail "Capfile locked at #{version}, but #{current_version} is loaded"
+      end
+    end
+
+    private
+    attr_reader :version
+
+
+    def match?
+      available =~ requested
+    end
+
+    def current_version
+      VERSION
+    end
+
+    def available
+      Gem::Dependency.new('cap', version)
+    end
+
+    def requested
+      Gem::Dependency.new('cap', current_version)
+    end
+
+  end
+end
diff --git a/spec/lib/capistrano/version_validator_spec.rb b/spec/lib/capistrano/version_validator_spec.rb
new file mode 100644
index 00000000..64385815
--- /dev/null
+++ b/spec/lib/capistrano/version_validator_spec.rb
@@ -0,0 +1,103 @@
+require 'spec_helper'
+
+module Capistrano
+
+  describe VersionValidator do
+    let(:validator) { VersionValidator.new(version) }
+    let(:version) { stub }
+
+    describe '#new' do
+      it 'takes a version' do
+        expect(validator)
+      end
+    end
+
+    describe '#verify' do
+      let(:current_version) { '3.0.1' }
+
+      subject { validator.verify }
+
+      before do
+        validator.stubs(:current_version).returns(current_version)
+      end
+
+      context 'with exact version' do
+        context 'valid' do
+          let(:version) { '3.0.1' }
+          it { should be_true }
+        end
+
+        context 'invalid - lower' do
+          let(:version) { '3.0.0' }
+
+          it 'fails' do
+            expect { subject }.to raise_error
+          end
+        end
+
+        context 'invalid - higher' do
+          let(:version) { '3.0.2' }
+
+          it 'fails' do
+            expect { subject }.to raise_error
+          end
+        end
+
+      end
+
+      context 'with optimistic versioning' do
+        context 'valid' do
+          let(:version) { '>= 3.0.0' }
+          it { should be_true }
+        end
+
+        context 'invalid - lower' do
+          let(:version) { '<= 2.0.0' }
+
+          it 'fails' do
+            expect { subject }.to raise_error
+          end
+        end
+      end
+
+
+
+      context 'with pessimistic versioning' do
+        context '2 decimal places' do
+          context 'valid' do
+            let(:version) { '~> 3.0.0' }
+            it { should be_true }
+          end
+
+          context 'invalid' do
+            let(:version) { '~> 3.1.0' }
+
+            it 'fails' do
+              expect { subject }.to raise_error
+            end
+          end
+        end
+
+        context '1 decimal place' do
+          let(:current_version) { '3.5.0' }
+
+          context 'valid' do
+            let(:version) { '~> 3.1' }
+            it { should be_true }
+          end
+
+          context 'invalid' do
+            let(:version) { '~> 3.6' }
+            it 'fails' do
+              expect { subject }.to raise_error
+            end
+          end
+        end
+
+      end
+
+    end
+
+  end
+
+end