Remove engine from the constructor arguments `Arel::Table`

It is never used outside of convenience methods which are only used in
tests. In practice, it just made constructing tables more complicated on
the rails side. This is the minimum possible change to remove the
constructor argument, but continue to have the tests passing.

I'm not sure if we have a reason to keep `project` and friends, and the
solution might actually just be to remove the engine from
`SelectManager` and friends. As such I've held off on deleting those
methods.

We need to figure out what to do with `Table#from`. It's old invocation,
which read `table.from(table)` was certainly nonsensical.

4 files changed, 49 insertions, 103 deletions

diff --git a/lib/arel/table.rb b/lib/arel/table.rb
index fb86c03404..d534c44fa1 100644
--- a/lib/arel/table.rb
+++ b/lib/arel/table.rb
@@ -11,20 +11,18 @@ module Arel
     # TableAlias and Table both have a #table_name which is the name of the underlying table
     alias :table_name :name
 
-    def initialize name, engine = Table.engine
+    def initialize name, options = {}
       @name    = name.to_s
-      @engine  = engine
       @columns = nil
       @aliases = []
-      @table_alias = nil
-
-      if Hash === engine
-        @engine  = engine[:engine] || Table.engine
-
-        # Sometime AR sends an :as parameter to table, to let the table know
-        # that it is an Alias.  We may want to override new, and return a
-        # TableAlias node?
-        @table_alias = engine[:as] unless engine[:as].to_s == @name
+      @engine = Table.engine
+
+      # Sometime AR sends an :as parameter to table, to let the table know
+      # that it is an Alias.  We may want to override new, and return a
+      # TableAlias node?
+      @table_alias = options[:as]
+      if @table_alias.to_s == @name
+        @table_alias = nil
       end
     end
 
@@ -34,12 +32,12 @@ module Arel
       end
     end
 
-    def from table
-      SelectManager.new(@engine, table)
+    def from engine = Table.engine
+      SelectManager.new(engine, self)
     end
 
     def join relation, klass = Nodes::InnerJoin
-      return from(self) unless relation
+      return from unless relation
 
       case relation
       when String, Nodes::SqlLiteral
@@ -47,7 +45,7 @@ module Arel
         klass = Nodes::StringJoin
       end
 
-      from(self).join(relation, klass)
+      from.join(relation, klass)
     end
 
     def outer_join relation
@@ -55,55 +53,39 @@ module Arel
     end
 
     def group *columns
-      from(self).group(*columns)
+      from.group(*columns)
     end
 
     def order *expr
-      from(self).order(*expr)
+      from.order(*expr)
     end
 
     def where condition
-      from(self).where condition
+      from.where condition
     end
 
     def project *things
-      from(self).project(*things)
+      from.project(*things)
     end
 
     def take amount
-      from(self).take amount
+      from.take amount
     end
 
     def skip amount
-      from(self).skip amount
+      from.skip amount
     end
 
     def having expr
-      from(self).having expr
+      from.having expr
     end
 
     def [] name
       ::Arel::Attribute.new self, name
     end
 
-    def select_manager
-      SelectManager.new(@engine)
-    end
-
-    def insert_manager
-      InsertManager.new(@engine)
-    end
-
-    def update_manager
-      UpdateManager.new(@engine)
-    end
-
-    def delete_manager
-      DeleteManager.new(@engine)
-    end
-
     def hash
-      # Perf note: aliases, table alias and engine is excluded from the hash
+      # Perf note: aliases and table alias is excluded from the hash
       #  aliases can have a loop back to this table breaking hashes in parent
       #  relations, for the vast majority of cases @name is unique to a query
       @name.hash
@@ -112,7 +94,6 @@ module Arel
     def eql? other
       self.class == other.class &&
         self.name == other.name &&
-        self.engine == other.engine &&
         self.aliases == other.aliases &&
         self.table_alias == other.table_alias
     end
diff --git a/test/nodes/test_table_alias.rb b/test/nodes/test_table_alias.rb
index 4aafd12b79..e30f97b748 100644
--- a/test/nodes/test_table_alias.rb
+++ b/test/nodes/test_table_alias.rb
@@ -5,27 +5,26 @@ module Arel
   module Nodes
     describe 'table alias' do
       it 'has an #engine which delegates to the relation' do
-        engine   = 'vroom'
-        relation = Table.new(:users, engine)
+        relation = OpenStruct.new(engine: 'vroom')
 
         node = TableAlias.new relation, :foo
-        node.engine.must_equal engine
+        node.engine.must_equal 'vroom'
       end
 
       describe 'equality' do
         it 'is equal with equal ivars' do
-          relation1 = Table.new(:users, 'vroom')
+          relation1 = Table.new(:users)
           node1     = TableAlias.new relation1, :foo
-          relation2 = Table.new(:users, 'vroom')
+          relation2 = Table.new(:users)
           node2     = TableAlias.new relation2, :foo
           array = [node1, node2]
           assert_equal 1, array.uniq.size
         end
 
         it 'is not equal with different ivars' do
-          relation1 = Table.new(:users, 'vroom')
+          relation1 = Table.new(:users)
           node1     = TableAlias.new relation1, :foo
-          relation2 = Table.new(:users, 'vroom')
+          relation2 = Table.new(:users)
           node2     = TableAlias.new relation2, :bar
           array = [node1, node2]
           assert_equal 2, array.uniq.size
diff --git a/test/test_select_manager.rb b/test/test_select_manager.rb
index 78b3a25928..f55b3877eb 100644
--- a/test/test_select_manager.rb
+++ b/test/test_select_manager.rb
@@ -110,14 +110,14 @@ module Arel
       describe 'having' do
         it 'converts strings to SQLLiterals' do
           table   = Table.new :users
-          mgr = table.from table
+          mgr = table.from
           mgr.having 'foo'
           mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo }
         end
 
         it 'can have multiple items specified separately' do
           table = Table.new :users
-          mgr = table.from table
+          mgr = table.from
           mgr.having 'foo'
           mgr.having 'bar'
           mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo AND bar }
@@ -125,7 +125,7 @@ module Arel
 
         it 'can have multiple items specified together' do
           table = Table.new :users
-          mgr = table.from table
+          mgr = table.from
           mgr.having 'foo', 'bar'
           mgr.to_sql.must_be_like %{ SELECT FROM "users" HAVING foo AND bar }
         end
@@ -135,7 +135,7 @@ module Arel
         it 'converts to sqlliterals' do
           table = Table.new :users
           right = table.alias
-          mgr   = table.from table
+          mgr   = table.from
           mgr.join(right).on("omg")
           mgr.to_sql.must_be_like %{ SELECT  FROM "users" INNER JOIN "users" "users_2" ON omg }
         end
@@ -143,7 +143,7 @@ module Arel
         it 'converts to sqlliterals with multiple items' do
           table = Table.new :users
           right = table.alias
-          mgr   = table.from table
+          mgr   = table.from
           mgr.join(right).on("omg", "123")
           mgr.to_sql.must_be_like %{ SELECT  FROM "users" INNER JOIN "users" "users_2" ON omg AND 123 }
         end
@@ -153,7 +153,7 @@ module Arel
     describe 'clone' do
       it 'creates new cores' do
         table   = Table.new :users, :as => 'foo'
-        mgr = table.from table
+        mgr = table.from
         m2 = mgr.clone
         m2.project "foo"
         mgr.to_sql.wont_equal m2.to_sql
@@ -161,7 +161,7 @@ module Arel
 
       it 'makes updates to the correct copy' do
         table   = Table.new :users, :as => 'foo'
-        mgr = table.from table
+        mgr = table.from
         m2 = mgr.clone
         m3 = m2.clone
         m2.project "foo"
@@ -173,7 +173,7 @@ module Arel
     describe 'initialize' do
       it 'uses alias in sql' do
         table   = Table.new :users, :as => 'foo'
-        mgr = table.from table
+        mgr = table.from
         mgr.skip 10
         mgr.to_sql.must_be_like %{ SELECT FROM "users" "foo" OFFSET 10 }
       end
@@ -182,14 +182,14 @@ module Arel
     describe 'skip' do
       it 'should add an offset' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.skip 10
         mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
       end
 
       it 'should chain' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.skip(10).to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
       end
     end
@@ -197,14 +197,14 @@ module Arel
     describe 'offset' do
       it 'should add an offset' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.offset = 10
         mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
       end
 
       it 'should remove an offset' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.offset = 10
         mgr.to_sql.must_be_like %{ SELECT FROM "users" OFFSET 10 }
 
@@ -214,7 +214,7 @@ module Arel
 
       it 'should return the offset' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.offset = 10
         assert_equal 10, mgr.offset
       end
@@ -379,13 +379,13 @@ module Arel
     describe 'ast' do
       it 'should return the ast' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         assert mgr.ast
       end
 
       it 'should allow orders to work when the ast is grepped' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.project Arel.sql '*'
         mgr.from table
         mgr.orders << Arel::Nodes::Ascending.new(Arel.sql('foo'))
@@ -406,7 +406,7 @@ module Arel
       # This should fail on other databases
       it 'adds a lock node' do
         table   = Table.new :users
-        mgr = table.from table
+        mgr = table.from
         mgr.lock.to_sql.must_be_like %{ SELECT FROM "users" FOR UPDATE }
       end
     end
diff --git a/test/test_table.rb b/test/test_table.rb
index 14256475ec..394a755727 100644
--- a/test/test_table.rb
+++ b/test/test_table.rb
@@ -47,12 +47,6 @@ module Arel
       assert_equal "INSERT INTO \"users\" VALUES(NULL)", im.to_sql
     end
 
-    it 'should return IM from insert_manager' do
-      im = @relation.insert_manager
-      assert_kind_of Arel::InsertManager, im
-      assert_equal im.engine, @relation.engine
-    end
-
     describe 'skip' do
       it 'should add an offset' do
         sm = @relation.skip 2
@@ -60,29 +54,6 @@ module Arel
       end
     end
 
-    describe 'select_manager' do
-      it 'should return an empty select manager' do
-        sm = @relation.select_manager
-        sm.to_sql.must_be_like 'SELECT'
-      end
-    end
-
-    describe 'update_manager' do
-      it 'should return an update manager' do
-        um = @relation.update_manager
-        assert_kind_of Arel::UpdateManager, um
-        assert_equal um.engine, @relation.engine
-      end
-    end
-
-    describe 'delete_manager' do
-      it 'should return a delete manager' do
-        dm = @relation.delete_manager
-        assert_kind_of Arel::DeleteManager, dm
-        assert_equal dm.engine, @relation.engine
-      end
-    end
-
     describe 'having' do
       it 'adds a having clause' do
         mgr = @relation.having @relation[:id].eq(10)
@@ -149,14 +120,9 @@ module Arel
     end
 
     describe 'new' do
-      it 'should accept an engine' do
-        rel = Table.new :users, 'foo'
-        rel.engine.must_equal 'foo'
-      end
-
       it 'should accept a hash' do
-        rel = Table.new :users, :engine => 'foo'
-        rel.engine.must_equal 'foo'
+        rel = Table.new :users, :as => 'foo'
+        rel.table_alias.must_equal 'foo'
       end
 
       it 'ignores as if it equals name' do
@@ -228,10 +194,10 @@ module Arel
 
     describe 'equality' do
       it 'is equal with equal ivars' do
-        relation1 = Table.new(:users, 'vroom')
+        relation1 = Table.new(:users)
         relation1.aliases     = %w[a b c]
         relation1.table_alias = 'zomg'
-        relation2 = Table.new(:users, 'vroom')
+        relation2 = Table.new(:users)
         relation2.aliases     = %w[a b c]
         relation2.table_alias = 'zomg'
         array = [relation1, relation2]
@@ -239,10 +205,10 @@ module Arel
       end
 
       it 'is not equal with different ivars' do
-        relation1 = Table.new(:users, 'vroom')
+        relation1 = Table.new(:users)
         relation1.aliases     = %w[a b c]
         relation1.table_alias = 'zomg'
-        relation2 = Table.new(:users, 'vroom')
+        relation2 = Table.new(:users)
         relation2.aliases     = %w[x y z]
         relation2.table_alias = 'zomg'
         array = [relation1, relation2]