Add schema dumper

lib/rein.rb

@@ -14,6 +14,7 @@
 require 'rein/schema'
 require 'rein/type/enum'
 require 'rein/view'
+require 'rein/schema_dumper'
 
 module ActiveRecord
   class Migration # :nodoc:
@@ -33,4 +34,8 @@ class Migration # :nodoc:
     include Rein::Type::Enum
     include Rein::View
   end
+
+  class SchemaDumper
+    prepend Rein::SchemaDumper
+  end
 end

lib/rein/schema_dumper.rb

@@ -0,0 +1,58 @@
+module Rein
+  # @api private
+  module SchemaDumper
+    def tables(stream)
+      super
+      check_constraints(stream)
+    end
+
+    def check_constraints(stream)
+      puts constraints.to_a
+
+      stream.puts if constraints.any?
+
+      constraints.each do |constraint|
+        column_name = constraint['column_name']
+        check_clause = constraint['check_clause']
+
+        case check_clause
+        when /#{column_name}\s+(>=|>|=|!=|<|<=)\s+(\d+)/
+          add_numericality_constraint_command(stream, constraint, $1, $2)
+        end
+      end
+    end
+
+    private
+
+    def constraints
+      @constraints ||= @connection.execute <<-SQL
+        select *
+        from information_schema.check_constraints as c, information_schema.constraint_column_usage as u
+        where c.constraint_name = u.constraint_name
+          and c.constraint_schema = 'public'
+          and u.constraint_schema = 'public'
+      SQL
+    end
+
+    def add_numericality_constraint_command(stream, constraint, operator, value)
+      table_name = constraint['table_name']
+      column_name = constraint['column_name']
+
+      definition = definition_from_numerical_operator(operator)
+      stream.puts <<-RUBY
+  add_numericality_constraint "#{table_name}", "#{column_name}", #{definition}: #{value}
+      RUBY
+    end
+
+    def definition_from_numerical_operator(operator)
+      case operator
+      when '>=' then 'greater_than_or_equal_to'
+      when '>'  then 'greater_than'
+      when '<=' then 'less_than_or_equal_to'
+      when '<'  then 'less_than'
+      when '='  then 'equal_to'
+      when '!=' then 'not_equal_to'
+      end
+    end
+  end
+end

spec/integration/reversible_spec.rb

@@ -37,6 +37,10 @@ def down(*args)
     Migrator.migrate
   end
 
+  after(:all) do
+    Migrator.migrate
+  end
+
   it 'reverses check constraints' do
     expect(TableConstraint.where(constraint_name: 'no_r_titles')).to exist
     Migrator.down(2)

spec/integration/schema_dumper_spec.rb

@@ -0,0 +1,12 @@
+require 'spec_helper'
+
+RSpec.describe Rein::SchemaDumper do
+  it 'dumps constraints from the database' do
+    stream = StringIO.new
+
+    ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, stream)
+
+    output = stream.string
+    expect(output).to include 'add_numericality_constraint "books", "published_month", greater_than_or_equal_to: 1'
+  end
+end