Issue 52

Add a dry run option for the runners that won't actually apply the changes but rather shows what would have happened.
Thanks to evonzee for the patch (although it was changed a bit)

doc/example/example-msbuild.proj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 	<PropertyGroup>
-	    <MigratorTasksPath>$(MSBuildProjectDirectory)/../bin</MigratorTasksPath>
+	    <MigratorTasksPath>$(MSBuildProjectDirectory)\..\..\build</MigratorTasksPath>
 	</PropertyGroup>
 
 	<!-- Migration-related targets, properties, etc. -->
@@ -14,7 +14,31 @@
 
         <Migrate Provider="MySql"
             Connectionstring="Data Source=localhost;Database=test;User Id=root;Password=;"
-            Directory="migrations"
+            Migrations="$(MSBuildProjectDirectory)\migrations\migrations.dll"
             To="$(SchemaVersion)"/>
     </Target>
-</Project>
+
+    <Target Name="Migrate-DryRun">
+        <CreateProperty Value="-1"  Condition="'$(SchemaVersion)'==''">
+            <Output TaskParameter="Value" PropertyName="SchemaVersion"/>
+        </CreateProperty>
+
+        <Migrate Provider="MySql"
+            Connectionstring="Data Source=localhost;Database=test;User Id=root;Password=;"
+            Migrations="$(MSBuildProjectDirectory)\migrations\migrations.dll"
+            To="$(SchemaVersion)"
+            DryRun="true"/>
+    </Target>
+
+    <Target Name="Migrate-Dump">
+        <CreateProperty Value="-1"  Condition="'$(SchemaVersion)'==''">
+            <Output TaskParameter="Value" PropertyName="SchemaVersion"/>
+        </CreateProperty>
+
+        <Migrate Provider="MySql"
+            Connectionstring="Data Source=localhost;Database=test;User Id=root;Password=;"
+            Migrations="$(MSBuildProjectDirectory)\migrations\migrations.dll"
+            To="$(SchemaVersion)"
+            ScriptFile="MSBuild-migrations.sql"/>
+    </Target>
+</Project>

doc/example/example-nant.build

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <project name="migrator" xmlns="http://nant.sf.net/release/0.85/nant.xsd">
-	<loadtasks assembly="../bin/Migrator.NAnt.dll" />
+	<loadtasks assembly="../../build/Migrator.NAnt.dll" />
 	<target name="migrate" description="Migrate the database">
 		<property name="version" value="-1" overwrite="false" />
 	  	<migrate
@@ -9,4 +9,24 @@
 	    	directory="migrations"
 	    	to="${version}" />
 	</target>
+
+	<target name="migrate-dryrun" description="Migrate the database">
+		<property name="version" value="-1" overwrite="false" />
+	  	<migrate
+	    	provider="MySql"
+	    	connectionstring="Data Source=localhost;Database=test;User Id=root;Password=;"
+	    	directory="migrations"
+	    	to="${version}" 
+            dryrun="true"/>
+	</target>
+
+	<target name="migrate-dump" description="Migrate the database">
+		<property name="version" value="-1" overwrite="false" />
+	  	<migrate
+	    	provider="MySql"
+	    	connectionstring="Data Source=localhost;Database=test;User Id=root;Password=;"
+	    	directory="migrations"
+	    	to="${version}" 
+            scriptFile="nant-migrations.sql"/>
+	</target>
 </project>

src/Migrator.Console/MigratorConsole.cs

@@ -28,6 +28,7 @@ public class MigratorConsole
 		private string _migrationsAssembly;
 		private bool _list = false;
 		private bool _trace = false;
+		private bool _dryrun = false;
 		private string _dumpTo;
 		private int _migrateTo = -1;
 		private string[] args;
@@ -80,6 +81,9 @@ public void Migrate()
 			CheckArguments();
 
 			Migrator mig = GetMigrator();
+            if (mig.DryRun)
+                mig.Logger.Log("********** Dry run! Not actually applying changes. **********");
+
 			if (_migrateTo == -1)
 				mig.MigrateToLastVersion();
 			else
@@ -137,6 +141,7 @@ public void PrintUsage()
 			Console.WriteLine("\t-{0}{1}", "list".PadRight(tab), "List migrations");
 			Console.WriteLine("\t-{0}{1}", "trace".PadRight(tab), "Show debug informations");
 			Console.WriteLine("\t-{0}{1}", "dump FILE".PadRight(tab), "Dump the database schema as migration code");
+			Console.WriteLine("\t-{0}{1}", "dryrun".PadRight(tab), "Simulation mode (don't actually apply/remove any migrations)");
 			Console.WriteLine();
 		}
 
@@ -155,6 +160,7 @@ private Migrator GetMigrator()
 
 			Migrator migrator = new Migrator(_provider, _connectionString, asm, _trace);
 			migrator.args = args;
+		    migrator.DryRun = _dryrun;
 			return migrator;
 		}
 
@@ -170,6 +176,10 @@ private void ParseArguments(string[] argv)
 				{
 					_trace = true;
 				}
+				else if (argv[i].Equals("-dryrun"))
+				{
+					_dryrun = true;
+				}
 				else if (argv[i].Equals("-version"))
 				{
 					_migrateTo = int.Parse(argv[i+1]);

src/Migrator.MSBuild/MigrateTask.cs

@@ -52,6 +52,7 @@ public class Migrate : Task
 		private string _connectionString;
 		private ITaskItem[] _migrationsAssembly;
 		private bool _trace;
+		private bool _dryrun;
 	    private string _scriptFile;
 
         private string _directory;
@@ -109,6 +110,12 @@ public bool Trace
 			get { return _trace; }
 		}
 
+		public bool DryRun
+		{
+			set { _dryrun = value; }
+			get { return _dryrun; }
+		}
+
         /// <summary>
         /// Gets value indicating whether to script the changes made to the database 
         /// to the file indicated by <see cref="ScriptFile"/>.
@@ -152,6 +159,7 @@ public override bool Execute()
         private void Execute(Assembly asm)
 	    {
             Migrator mig = new Migrator(Provider, ConnectionString, asm, Trace, new TaskLogger(this));
+            mig.DryRun = DryRun;
             if (ScriptChanges)
             {
                 using (StreamWriter writer = new StreamWriter(ScriptFile))
@@ -168,6 +176,9 @@ private void Execute(Assembly asm)
 
 	    private void RunMigration(Migrator mig)
 	    {
+            if (mig.DryRun)
+                mig.Logger.Log("********** Dry run! Not actually applying changes. **********");
+
 	        if (_to == -1)
 	            mig.MigrateToLastVersion();
 	        else

src/Migrator.NAnt/MigrateTask.cs

@@ -42,6 +42,7 @@ public class MigrateTask : Task
 		private string _connectionString;
 		private FileInfo _migrationsAssembly;
 		private bool _trace;
+		private bool _dryrun;
         private string _scriptFile;
 
         private string _directory;
@@ -100,6 +101,13 @@ public bool Trace
 			set { _trace = value; }
 			get { return _trace; }
 		}
+
+		[TaskAttribute("dryrun")]
+		public bool DryRun
+		{
+			set { _dryrun = value; }
+			get { return _dryrun; }
+		}
 
         /// <summary>
         /// Gets value indicating whether to script the changes made to the database 
@@ -140,6 +148,7 @@ protected override void ExecuteTask()
         private void Execute(Assembly asm)
         {
             Migrator mig = new Migrator(Provider, ConnectionString, asm, Trace, new TaskLogger(this));
+            mig.DryRun = DryRun;
             if (ScriptChanges)
             {
                 using (StreamWriter writer = new StreamWriter(ScriptFile))
@@ -156,6 +165,9 @@ private void Execute(Assembly asm)
 
         private void RunMigration(Migrator mig)
         {
+            if (mig.DryRun)
+                mig.Logger.Log("********** Dry run! Not actually applying changes. **********");
+
             if (_to == -1)
                 mig.MigrateToLastVersion();
             else

src/Migrator/BaseMigrate.cs

@@ -10,6 +10,7 @@ public abstract class BaseMigrate
         protected List<long> _availableMigrations;
         protected List<long> _original;
         protected long _current;
+        protected bool _dryrun;
 
         protected BaseMigrate(List<long> availableMigrations, ITransformationProvider provider, ILogger logger)
         {
@@ -35,6 +36,12 @@ public virtual long Current
             protected set { _current = value; }
         }
 
+        public virtual bool DryRun
+        {
+            get { return _dryrun; }
+            set { _dryrun = value; }
+        }
+
         public abstract long Previous { get; }
         public abstract long Next { get; }
 

src/Migrator/Compile/ScriptEngine.cs

@@ -2,6 +2,7 @@
 using System.CodeDom.Compiler;
 using System.IO;
 using System.Reflection;
+using Migrator.Framework;
 
 namespace Migrator.Compile
 {
@@ -75,8 +76,9 @@ private CompilerParameters SetupCompilerParams()
 
         private string FullAssemblyPath(string assemblyName)
         {
-            string assemblyLocation = Assembly.GetExecutingAssembly().Location;
-            return Path.Combine(Directory.GetParent(assemblyLocation).FullName, "Migrator.Framework.dll");
+            string assemblyLocation = Assembly.GetAssembly(typeof(MigrationAttribute)).Location;
+            Console.Out.WriteLine("Assembly Path: {0}", assemblyLocation);
+            return Path.Combine(Directory.GetParent(assemblyLocation).FullName, assemblyName);
         }
     }
 }

src/Migrator/MigrateAnywhere.cs

@@ -14,12 +14,11 @@ public class MigrateAnywhere : BaseMigrate
         public MigrateAnywhere(List<long> availableMigrations, ITransformationProvider provider, ILogger logger)
             : base(availableMigrations, provider, logger)
         {
-            _current = 0;
-            if (provider.AppliedMigrations.Count > 0)
-            {
-                _current = provider.AppliedMigrations[provider.AppliedMigrations.Count - 1];
-            }
-            _goForward = false;
+			_current = 0;
+			if (provider.AppliedMigrations.Count > 0) {
+				_current = provider.AppliedMigrations[provider.AppliedMigrations.Count - 1];
+			}
+			_goForward = false;
         }
 
         public override long Next
@@ -62,27 +61,39 @@ public override bool Continue(long version)
         public override void Migrate(IMigration migration)
         {
             _provider.BeginTransaction();
-            MigrationAttribute attr =
-                (MigrationAttribute) Attribute.GetCustomAttribute(migration.GetType(), typeof (MigrationAttribute));
-
-            if (_provider.AppliedMigrations.Contains(attr.Version))
-            {
-                // we're removing this one
-                _logger.MigrateDown(Current, migration.Name);
-                migration.Down();
-                _provider.MigrationUnApplied(attr.Version);
-                _provider.Commit();
-                migration.AfterDown();
+            MigrationAttribute attr = (MigrationAttribute)Attribute.GetCustomAttribute(migration.GetType(), typeof(MigrationAttribute));
+
+            if (_provider.AppliedMigrations.Contains(attr.Version)) {
+            	RemoveMigration(migration, attr);
+            } else {
+            	ApplyMigration(migration, attr);
             }
-            else
+        }
+
+        private void ApplyMigration(IMigration migration, MigrationAttribute attr)
+        {
+            // we're adding this one
+            _logger.MigrateUp(Current, migration.Name);
+            if(! DryRun)
             {
-                // we're adding this one
-                _logger.MigrateUp(Current, migration.Name);
                 migration.Up();
                 _provider.MigrationApplied(attr.Version);
                 _provider.Commit();
                 migration.AfterUp();
             }
         }
+
+        private void RemoveMigration(IMigration migration, MigrationAttribute attr)
+        {
+            // we're removing this one
+            _logger.MigrateDown(Current, migration.Name);
+            if (! DryRun)
+            {
+                migration.Down();
+                _provider.MigrationUnApplied(attr.Version);
+                _provider.Commit();
+                migration.AfterDown();
+            }
+        }
     }
-}
+}

src/Migrator/Migrator.cs

@@ -29,6 +29,7 @@ public class Migrator
         private readonly MigrationLoader _migrationLoader;
 
         private ILogger _logger = new Logger(false);
+        protected bool _dryrun;
         private string[] _args;
 
         public string[] args
@@ -76,7 +77,8 @@ public List<Type> MigrationsTypes
         }
 
         /// <summary>
-        /// Run all migrations up to the latest.
+        /// Run all migrations up to the latest.  Make no changes to database if
+        /// dryrun is true.
         /// </summary>
         public void MigrateToLastVersion()
         {
@@ -104,6 +106,12 @@ public ILogger Logger
             }
         }
 
+        public virtual bool DryRun
+        {
+            get { return _dryrun; }
+            set { _dryrun = value; }
+        }
+
         /// <summary>
         /// Migrate the database to a specific version.
         /// Runs all migration between the actual version and the
@@ -112,6 +120,7 @@ public ILogger Logger
         /// the <c>Up()</c> method will be invoked.
         /// If <c>version</c> lower then the current version,
         /// the <c>Down()</c> method of previous migration will be invoked.
+        /// If <c>dryrun</c> is set, don't write any changes to the database.
         /// </summary>
         /// <param name="version">The version that must became the current one</param>
         public void MigrateTo(long version)
@@ -125,6 +134,7 @@ public void MigrateTo(long version)
 
             bool firstRun = true;
             BaseMigrate migrate = BaseMigrate.GetInstance(_migrationLoader.GetAvailableMigrations(), _provider, _logger);
+            migrate.DryRun = DryRun;
             Logger.Started(migrate.AppliedVersions, version);
 
             while (migrate.Continue(version))

src/config/AssemblyInfo.cs

@@ -24,4 +24,4 @@
 //      Build Number
 //      Revision
 //
-[assembly: AssemblyVersion("0.7.0.*")]
+[assembly: AssemblyVersion("0.8.0.*")]