migrate automatically

MIT-LICENSE

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+Copyright (c) 2007 PJ Hyett
+
+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

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+== AutoMigrations
+
+Forget migrations, auto-migrate!
+
+
+== Usage
+
+Write out your schema (or use an existing one)
+
+  $ cat db/schema.rb
+
+  ActiveRecord::Schema.define do
+
+    create_table :posts do |t|
+      t.string   :title
+      t.text     :body
+      t.timestamps
+    end
+
+  end
+
+  $ rake db:auto:migrate
+
+  Created posts table
+
+...a few days later
+
+  $ cat db/schema.rb
+
+  ActiveRecord::Schema.define do
+
+    create_table :posts do |t|
+      t.string   :title
+      t.text     :content
+      t.timestamps
+    end
+
+  end
+
+  $ rake db:auto:migrate
+  -- add_column("posts", :content, :text)
+     -> 0.0307s
+  -- remove_column("posts", "body")
+     -> 0.0311s
+
+Found a bug?  Sweet.  Add it at the Lighthouse: 
+  http://err.lighthouseapp.com/projects/466-plugins/tickets/new
+
+Feature requests are welcome. 
+
+* PJ Hyett [ pjhyett@gmail.com ]

Rakefile

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+require 'rake'
+require 'rake/testtask'
+require 'rake/rdoctask'
+
+desc 'Default: run unit tests.'
+task :default => :test
+
+desc 'Test the auto_migrations plugin.'
+Rake::TestTask.new(:test) do |t|
+  t.libs << 'lib'
+  t.pattern = 'test/**/*_test.rb'
+  t.verbose = true
+end
+
+desc 'Generate documentation for the auto_migrations plugin.'
+Rake::RDocTask.new(:rdoc) do |rdoc|
+  files = ['README', 'LICENSE', 'lib/**/*.rb']
+  rdoc.rdoc_files.add(files)
+  rdoc.main = "README" # page to start on
+  rdoc.title = "auto_migrations"
+  rdoc.template = File.exists?(t="/Users/chris/ruby/projects/err/rock/template.rb") ? t : "/var/www/rock/template.rb"
+  rdoc.rdoc_dir = 'doc' # rdoc output folder
+  rdoc.options << '--inline-source'
+end

init.rb

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+require 'auto_migrations'
+ActiveRecord::Migration.send :include, AutoMigrations

lib/auto_migrations.rb

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+module AutoMigrations
+
+  def self.run
+    # Turn off schema_info code for auto-migration
+    class << ActiveRecord::Schema
+      alias :old_define :define
+      def define(info={}, &block) instance_eval(&block) end
+    end
+
+    load(File.join(RAILS_ROOT, 'db', 'schema.rb'))
+    ActiveRecord::Migration.drop_unused_tables
+    ActiveRecord::Migration.drop_unused_indexes
+
+    class << ActiveRecord::Schema
+      alias :define :old_define
+    end
+  end
+
+  def self.schema_to_migration
+    schema = File.read(File.join(RAILS_ROOT, "db", "schema.rb"))
+    schema.gsub!(/#(.)+\n/, '')
+    schema.sub!(/ActiveRecord::Schema.define(.+)do[ ]?\n/, '')
+    schema.gsub!(/^/, '  ')
+    schema = "class InitialSchema < ActiveRecord::Migration\n  def self.up\n" + schema
+    schema << "\n  def self.down\n"
+    schema << (ActiveRecord::Base.connection.tables - ["schema_info"]).map do |table| 
+                "    drop_table :#{table}\n"
+              end.join
+    schema << "  end\nend\n"
+    migration_file = File.join(RAILS_ROOT, "db", "migrate", "001_initial_schema.rb")
+    File.open(migration_file, "w") { |f| f << schema }
+    puts "Migration created at db/migrate/001_initial_schema.rb"
+  end
+
+  def self.included(base)
+    base.extend ClassMethods
+    class << base
+      cattr_accessor :tables_in_schema, :indexes_in_schema
+      self.tables_in_schema, self.indexes_in_schema = [], []
+      alias_method_chain :method_missing, :auto_migration
+    end
+  end
+
+  module ClassMethods
+
+    def method_missing_with_auto_migration(method, *args, &block)
+      case method
+      when :create_table
+        auto_create_table(method, *args, &block)
+      when :add_index
+        auto_add_index(method, *args, &block)
+      else
+        method_missing_without_auto_migration(method, *args, &block) 
+      end
+    end
+
+    def auto_create_table(method, *args, &block)
+      table_name = args.shift.to_s    
+      options    = args.pop || {}
+
+      (self.tables_in_schema ||= []) << table_name
+
+      # Table doesn't exist, create it
+      unless ActiveRecord::Base.connection.tables.include?(table_name)
+        return method_missing_without_auto_migration(method, *[table_name, options], &block)
+      end
+
+      # Grab database columns
+      fields_in_db = ActiveRecord::Base.connection.columns(table_name).inject({}) do |hash, column|
+        hash[column.name] = column
+        hash
+      end
+
+      # Grab schema columns (lifted from active_record/connection_adapters/abstract/schema_statements.rb)
+      table_definition = ActiveRecord::ConnectionAdapters::TableDefinition.new(ActiveRecord::Base.connection)
+      table_definition.primary_key(options[:primary_key] || "id") unless options[:id] == false
+      yield table_definition
+      fields_in_schema = table_definition.columns.inject({}) do |hash, column|
+        hash[column.name.to_s] = column
+        hash
+      end
+
+      # Add fields to db new to schema
+      (fields_in_schema.keys - fields_in_db.keys).each do |field|
+        column = fields_in_schema[field]
+        add_column table_name, column.name, column.type.to_sym, :limit => column.limit, :precision => column.precision, 
+          :scale => column.scale, :default => column.default, :null => column.null
+      end
+
+      # Remove fields from db no longer in schema
+      (fields_in_db.keys - fields_in_schema.keys & fields_in_db.keys).each do |field|
+        column = fields_in_db[field]
+        remove_column table_name, column.name
+      end
+
+      # Change field type if schema is different from db
+      (fields_in_schema.keys & fields_in_db.keys).each do |field|
+        if (field != 'id') && (fields_in_schema[field].type.to_sym != fields_in_db[field].type.to_sym)
+          change_column table_name, fields_in_schema[field].name.to_sym, fields_in_schema[field].type.to_sym
+        end
+      end
+    end
+
+    def auto_add_index(method, *args, &block)      
+      table_name = args.shift.to_s
+      fields     = Array(args.shift).map(&:to_s)
+      options    = args.shift
+
+      index_name = options[:name] if options  
+      index_name ||= "index_#{table_name}_on_#{fields.join('_and_')}"
+
+      (self.indexes_in_schema ||= []) << index_name
+
+      unless ActiveRecord::Base.connection.indexes(table_name).detect { |i| i.name == index_name }
+        method_missing_without_auto_migration(method, *[table_name, fields, options], &block)
+      end
+    end
+
+    def drop_unused_tables
+      (ActiveRecord::Base.connection.tables - tables_in_schema - ["schema_info"]).each do |table|
+        drop_table table
+      end
+    end
+
+    def drop_unused_indexes
+      tables_in_schema.each do |table_name|
+        indexes_in_db = ActiveRecord::Base.connection.indexes(table_name).map(&:name)
+        (indexes_in_db - indexes_in_schema & indexes_in_db).each do |index_name|
+          remove_index table_name, :name => index_name
+        end
+      end
+    end
+
+  end
+
+end

tasks/auto_migrations_tasks.rake

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+namespace :db do
+  namespace :auto do
+    desc "Use schema.rb to auto-migrate"
+    task :migrate => :environment do
+      AutoMigrations.run
+    end 
+  end
+
+  namespace :schema do
+    desc "Create migration from schema.rb"
+    task :to_migration => :environment do
+      AutoMigrations.schema_to_migration
+    end
+  end
+end

test/auto_migrations_test.rb

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+require 'test/unit'
+
+class AutoMigrationsTest < Test::Unit::TestCase
+  # Replace this with your real tests.
+  def test_this_plugin
+    flunk
+  end
+end