From f0b782d060f76647e36adc40fe5fe818ec8e2c66 Mon Sep 17 00:00:00 2001
From: Piotr Sarnacki <drogus@gmail.com>
Date: Fri, 9 Dec 2011 20:07:29 +0100
Subject: [PATCH] Allow to filter migrations by passing a block

Example:
  ActiveRecord::Migrator.migrate(path) do |migration|
    migration.name =~ /User/
  end

The above example will migrate only migrations with User in
the name
---
 activerecord/lib/active_record/migration.rb | 22 ++++++++++++---------
 activerecord/test/cases/migration_test.rb   | 18 +++++++++++++++++
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 97ac39a350..46464783fd 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -528,16 +528,16 @@ module ActiveRecord
       attr_writer :migrations_paths
       alias :migrations_path= :migrations_paths=
 
-      def migrate(migrations_paths, target_version = nil)
+      def migrate(migrations_paths, target_version = nil, &block)
         case
           when target_version.nil?
-            up(migrations_paths, target_version)
+            up(migrations_paths, target_version, &block)
           when current_version == 0 && target_version == 0
             []
           when current_version > target_version
-            down(migrations_paths, target_version)
+            down(migrations_paths, target_version, &block)
           else
-            up(migrations_paths, target_version)
+            up(migrations_paths, target_version, &block)
         end
       end
 
@@ -549,12 +549,12 @@ module ActiveRecord
         move(:up, migrations_paths, steps)
       end
 
-      def up(migrations_paths, target_version = nil)
-        self.new(:up, migrations_paths, target_version).migrate
+      def up(migrations_paths, target_version = nil, &block)
+        self.new(:up, migrations_paths, target_version).migrate(&block)
       end
 
-      def down(migrations_paths, target_version = nil)
-        self.new(:down, migrations_paths, target_version).migrate
+      def down(migrations_paths, target_version = nil, &block)
+        self.new(:down, migrations_paths, target_version).migrate(&block)
       end
 
       def run(direction, migrations_paths, target_version)
@@ -657,7 +657,7 @@ module ActiveRecord
       end
     end
 
-    def migrate
+    def migrate(&block)
       current = migrations.detect { |m| m.version == current_version }
       target = migrations.detect { |m| m.version == @target_version }
 
@@ -674,6 +674,10 @@ module ActiveRecord
 
       ran = []
       runnable.each do |migration|
+        if block && !block.call(migration)
+          next
+        end
+
         Base.logger.info "Migrating to #{migration.name} (#{migration.version})" if Base.logger
 
         seen = migrated.include?(migration.version.to_i)
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index b5fae3b7d3..1e68911ab3 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -1235,6 +1235,24 @@ if ActiveRecord::Base.connection.supports_migrations?
       assert_raise(ActiveRecord::StatementInvalid) { Reminder.find(:first) }
     end
 
+    def test_filtering_migrations
+      assert !Person.column_methods_hash.include?(:last_name)
+      assert !Reminder.table_exists?
+
+      name_filter = lambda { |migration| migration.name == "ValidPeopleHaveLastNames" }
+      ActiveRecord::Migrator.up(MIGRATIONS_ROOT + "/valid", &name_filter)
+
+      Person.reset_column_information
+      assert Person.column_methods_hash.include?(:last_name)
+      assert_raise(ActiveRecord::StatementInvalid) { Reminder.find(:first) }
+
+      ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid", &name_filter)
+
+      Person.reset_column_information
+      assert !Person.column_methods_hash.include?(:last_name)
+      assert_raise(ActiveRecord::StatementInvalid) { Reminder.find(:first) }
+    end
+
     class MockMigration < ActiveRecord::Migration
       attr_reader :went_up, :went_down
       def initialize