README

We've all been there. You have an application in production, and now one of the database tables needs a structural change. You can't manually go in and change all the affected database rows. So what do you do? Put the logic in a migration? Seems a little risky, no?

Morpher is a Laravel package that provides a unified pattern of transforming data between database migrations. It allows you to keep your migration logic clean and terse and move responsibility for data manipulation to a more appropriate location. It also provides a robust way to write tests for these transformations, which otherwise proves to be a real challenge.

Installation

composer require ricorocks-digital-agency/morpher

It's not required, but you might want to publish the config file:

php artisan vendor:publish --tag=morpher

Create your first Morph

Let's set up an example scenario. Your users table has a single name column, but you now need to separate it out into first_name and last_name columns. Your application has been live for a little while, so there is going to be a need to perform a data transformation.

You start by creating a migration:

php artisan make:migration split_names_on_users_table

That migration's up method might look something like this:

public function up()
{
    Schema::table('users', function (Blueprint $table) {
        $table->dropColumn('name');
        $table->addColumn('first_name')->nullable();
        $table->addColumn('last_name')->nullable();
    });
}

So, how do we go about taking all of the existing names, preparing the data, and inserting it into our new table?

Let's start by creating out first Morph:

php artisan make:morph SplitUserNames

This will create a new class in database/morphs called SplitUserNames. Our next step is to link our migration to our new Morph. We can do this using the $migration property in the morph class:

protected static $migration = SplitNamesOnUsersTable::class;

If you need more complex logic, you can instead override the migration method and return a migration class name that way.

⚡ Working with anonymous migrations? You can instead use the filename of the migration as the value of the $migration property. For example: protected static $migration = "2021_05_01_000000_create_some_anonymous_table";

Our next task is to describe our Morph. In the app/Morphs/SplitUserNames class, we need to do the following:

Retrieve the current names prior to the migration being run.
Split the names into first and last names.
Insert the names after the migration has finished.

To accomplish this, our Morph might look as follows:

class SplitUserNames extends Morph
{
    protected static $migration = SplitNamesOnUsersTable::class;
    protected $newNames;
    
    public function prepare()
    {
        // Get all of the names along with their ID
        $names = DB::table('users')->select(['id', 'name'])->get();
        
        // Set a class property with the mapped version of the names
        $this->newNames = $names->map(function($data) {
            $nameParts = $this->splitName($data->name);
            return ['id' => $data->id, 'first_name' => $nameParts[0], 'last_name' => $nameParts[1]];
        });
    }
    
    protected function splitName($name)
    {
        // ...return some splitting logic here
    }

    public function run()
    {
        // Now we run the database query based on our transformed data
        DB::table('users')->upsert($this->newNames->toArray(), 'id');
    }
}

Now, when we run php artisan migrate, this Morph will run automatically.

Lifecycle

It helps to understand the lifecycle that a Morph goes through in order to make full use it.

When a Morph is linked to a migration, and that migration's up method is run (usually from migrating the database), the following happens (in order):

The prepare method will be called on the Morph class. You can do anything you need to prepare data here.
The migration will run.
The canRun method will be called on the Morph class. Returning false in this method will stop the process here.
The run method will be called on the Morph class. This is where you should perform your data transformations.

Testing Morphs

One of the biggest challenges presented by data morphing is writing feature tests. It becomes very tricky to insert data to test on prior to the morph taking place. And yet, automated tests are so important when the code you're running will be modifying real data. Morpher makes the process of testing data a breeze so that you no longer have to compromise.

To get started, we recommend creating a separate test case (or more than one test case) per Morph you'd like to write tests for. Add the TestsMorphs trait to that test class, and add the supportMorphs call to end of the setUp method.

use RicorocksDigitalAgency\Morpher\Support\TestsMorphs;

class UserMorphTest extends TestCase {

    use TestsMorphs;
    
    protected function setUp(): void
    {
        parent::setUp();
        $this->supportMorphs();
    }

}

⚠️ The TestsMorphs trait conflicts with other database traits, such as RefreshDatabase or DatabaseTransactions. As such, ensure that your morph test cases are isolated (in separate test classes) from other tests in your suite.

With that done, you can get to work writing your tests! In order to do this, we provide a robust inspection API to facilitate Morph tests.

use RicorocksDigitalAgency\Morpher\Facades\Morpher;

class UserMorphTest extends TestCase {

    // ...After setup
    
    public function test_it_translates_the_user_names_correctly() {
        Morpher::test(UserMorph::class)
            ->beforeThisMigration(function($morph) {
                /**
                 * We use the `beforeMigrating` hook to allow for "old"
                 * data creation. In our user names example, we'll
                 * create users with combined forename and surname.  
                 */
                 DB::table('users')->insert([['name' => 'Joe Bloggs'], ['name' => 'Luke Downing']]);
            })
            ->before(function($morph) {
                /**
                 * We use the `before` hook to perform any expectations 
                 * after the migration has run but before the Morph
                 * has been executed.
                 */
                 $this->assertCount(2, User::all());
            })
            ->after(function($morph) {
                /**
                 * We use the `after` hook to perform any expectations 
                 * after the morph has finished running. For example,
                 * we would expect data to have been transformed. 
                 */
                 [$joe, $luke] = User::all();
                 
                 $this->assertEquals("Joe", $joe->forename);
                 $this->assertEquals("Bloggs", $joe->surname);
                 
                 $this->assertEquals("Luke", $luke->forename);
                 $this->assertEquals("Downing", $luke->surname);
            });
    }

}

As you can see, there are several inspections methods we can make use of to fully test our Morphs. Note that you only need to use the inspections relevant to your particular Morph.

`beforeThisMigration`

This method is run prior to the migration connected to the Morph being run on the database. It is also run prior to the prepare method on your Morph being called. Seen as your tests won't have "old" data for your Morph to alter, you can use this method to create fake data ready for your Morph to use.

Note that in most cases, your Laravel Factories will likely be outdated, so you may have to resort to manual methods such as the DB Facade. You could also create a versioned Factory that uses the old data structure.

`before`

This method is executed prior to the run method being called on your Morph, but after the prepare method. You could use this as an opportunity to make sure your prepare method has collected the expected data and stored it on the Morph object, if your Morph needs to perform that step.

`after`

This method is executed after the run method has been called on your Morph. You should use this to check that the data migration has run successfully and that your data has actually been transformed.

Disabling Morphs

It may be helpful, particularly in local development where you destroy and rebuild the database regularly, to disable Morphs from running. To do this, add the following to your environment file:

RUN_MORPHS=false

Notes and Considerations

Everything in the run method is encapsulated in a database transaction. This means that if there is an exception whilst running your morph, no data changes will be persisted.
It's important to remember that this package isn't magic. If you do something stupid to the data in your database, there is no going back. Back up your data before migrating.
You can override the canRun method to stop a faulty data set ruining your database. Perform any checks you want in this method, and just return a boolean to tell us if we should go ahead.
Want to write your progress to the console during a Morph? You can do so using the $this->console property on the Morph class!

ricorocks-digital-agency / morpher

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