Add initial support for Query Objects

A new main component of Rectify is the Query Object. It allows a
database query to be encapsulated into a class. This allows logic that
is specific to the query as well as the query itself to be removed from
the ActiveRecord model as another strategy to reducing their size.

Query Objects need to be derived from `Rectify::Query` and must
implement the `query` method that returns either an
`ActiveRecord::Relation` or an array (via
`ActiveRecord::Quering#find_by_sql`)

This commit also adds a simple way to stub Query Objects with the
`stub_query` RSpec helper.

See the readme for full details of how to use Query Objects in a Rails
app.

.gitignore

@@ -1 +1,2 @@
 *.gem
+*.sqlite3

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rectify (0.2.0)
+    rectify (0.3.0)
       activemodel (~> 4.2, >= 4.2.0)
       activerecord (~> 4.2, >= 4.2.0)
       activesupport (~> 4.2, >= 4.2.0)
@@ -77,6 +77,7 @@ GEM
       rails-deprecated_sanitizer (>= 1.0.1)
     rails-html-sanitizer (1.0.3)
       loofah (~> 2.0)
+    rake (10.4.2)
     rspec (3.4.0)
       rspec-core (~> 3.4.0)
       rspec-expectations (~> 3.4.0)
@@ -93,6 +94,7 @@ GEM
       rspec-support (~> 3.4.0)
     rspec-support (3.4.1)
     slop (3.6.0)
+    sqlite3 (1.3.11)
     thread_safe (0.3.5)
     tzinfo (1.2.2)
       thread_safe (~> 0.1)
@@ -111,9 +113,11 @@ DEPENDENCIES
   actionpack (~> 4.2, >= 4.2.0)
   awesome_print (~> 1.6)
   pry (~> 0.10.3)
+  rake
   rectify!
   rspec (~> 3.4)
   rspec-collection_matchers (~> 1.1, >= 1.1.2)
+  sqlite3
   wisper-rspec (~> 0.0.2)
 
 BUNDLED WITH

Rakefile

@@ -0,0 +1,50 @@
+# Stolen from https://gist.github.com/schickling/6762581
+# Thank you <3
+require "yaml"
+require "active_record"
+
+namespace :db do
+  db_config = YAML.load(File.open("spec/config/database.yml"))
+
+  desc "Migrate the database"
+  task :migrate do
+    ActiveRecord::Base.establish_connection(db_config)
+    ActiveRecord::Migrator.migrate("spec/db/migrate")
+    Rake::Task["db:schema"].invoke
+    puts "Database migrated."
+  end
+
+  desc "Create a db/schema.rb file that is portable against any supported DB"
+  task :schema do
+    ActiveRecord::Base.establish_connection(db_config)
+    require "active_record/schema_dumper"
+    filename = "spec/db/schema.rb"
+    File.open(filename, "w:utf-8") do |file|
+      ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
+    end
+  end
+end
+
+namespace :g do
+  desc "Generate migration"
+  task :migration do
+    name      = ARGV[1] || fail("Specify name: rake g:migration your_migration")
+    timestamp = Time.now.strftime("%Y%m%d%H%M%S")
+    folder    = "../spec/db/migrate"
+    path      = File.expand_path("#{folder}/#{timestamp}_#{name}.rb", __FILE__)
+
+    migration_class = name.split("_").map(&:capitalize).join
+
+    File.open(path, "w") do |file|
+      file.write <<-EOF.strip_heredoc
+        class #{migration_class} < ActiveRecord::Migration
+          def change
+          end
+        end
+      EOF
+    end
+
+    puts "Migration #{path} created"
+    abort # needed stop other tasks
+  end
+end

lib/rectify.rb

@@ -10,4 +10,6 @@
 require "rectify/form"
 require "rectify/command"
 require "rectify/presenter"
+require "rectify/query"
 require "rectify/controller_helpers"
+require "rectify/errors"

lib/rectify/errors.rb

@@ -0,0 +1,11 @@
+module Rectify
+  class UnableToComposeQueries < StandardError
+    def initialize(query, other)
+      super(
+        "Unable to composite queries #{query.class.name} and " \
+        "#{other.class.name}. You cannot compose queries where #query " \
+        "returns an ActiveRecord::Relation in one and an array in the other."
+      )
+    end
+  end
+end

lib/rectify/query.rb

@@ -0,0 +1,65 @@
+module Rectify
+  module SqlQuery
+    def query
+      model.find_by_sql([sql, params])
+    end
+  end
+
+  class Query
+    def initialize(scope = ActiveRecord::NullRelation)
+      @scope = scope
+    end
+
+    def query
+      @scope
+    end
+
+    def |(other)
+      if relation? && other.relation?
+        Rectify::Query.new(cached_query.merge(other.cached_query))
+      elsif eager? && other.eager?
+        Rectify::Query.new(cached_query | other.cached_query)
+      else
+        fail UnableToComposeQueries.new(self, other)
+      end
+    end
+
+    def count
+      cached_query.count
+    end
+
+    def first
+      cached_query.first
+    end
+
+    def each(&block)
+      cached_query.each(&block)
+    end
+
+    def exists?
+      return cached_query.exists? if relation?
+
+      cached_query.present?
+    end
+
+    def none?
+      !exists?
+    end
+
+    def to_a
+      cached_query.to_a
+    end
+
+    def relation?
+      cached_query.is_a?(ActiveRecord::Relation)
+    end
+
+    def eager?
+      cached_query.is_a?(Array)
+    end
+
+    def cached_query
+      @cached_query ||= query
+    end
+  end
+end

lib/rectify/rspec.rb

@@ -0,0 +1,3 @@
+require "rectify/rspec/stub_query"
+require "rectify/rspec/helpers"
+require "rectify/rspec/matchers"

lib/rectify/rspec/helpers.rb

@@ -0,0 +1,10 @@
+module Rectify
+  module RSpec
+    module Helpers
+      def stub_query(query_class, options = {})
+        results = options.fetch(:results, [])
+        allow(query_class).to receive(:new) { StubQuery.new(results) }
+      end
+    end
+  end
+end

lib/rectify/rspec/matchers.rb

@@ -0,0 +1,51 @@
+require "rspec/expectations"
+
+module Rectify
+  module DatabaseReporting
+    SQL_TO_IGNORE = /
+      pg_table|
+      pg_attribute|
+      pg_namespace|
+      current_database|
+      information_schema|
+      ^TRUNCATE TABLE|
+      ^ALTER TABLE|
+      ^BEGIN|
+      ^COMMIT|
+      ^ROLLBACK|
+      ^RELEASE|
+      ^SAVEPOINT|
+      ^SHOW|
+      ^PRAGMA
+    /xi
+  end
+end
+
+RSpec::Matchers.define :make_database_queries_of do |expected|
+  supports_block_expectations
+
+  queries = []
+
+  match do |proc|
+    ActiveSupport::Notifications
+      .subscribe("sql.active_record") do |_, _, _, _, query|
+        sql = query[:sql]
+
+        unless Rectify::DatabaseReporting::SQL_TO_IGNORE.match(sql)
+          queries << sql
+        end
+      end
+
+    proc.call
+
+    queries.size == expected
+  end
+
+  failure_message do |_|
+    all_queries = queries.join("\n")
+
+    "expected the number of queries to be #{expected} " \
+    "but there were #{queries.size}.\n\n" \
+    "Here are the queries that were made:\n\n#{all_queries}"
+  end
+end

lib/rectify/rspec/stub_query.rb

@@ -0,0 +1,13 @@
+module Rectify
+  module RSpec
+    class StubQuery < Query
+      def initialize(results)
+        @results = Array(results)
+      end
+
+      def query
+        @results
+      end
+    end
+  end
+end

lib/rectify/version.rb

@@ -1,3 +1,3 @@
 module Rectify
-  VERSION = "0.2.0"
+  VERSION = "0.3.0"
 end