Generate YAML fixture for DataObjects

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0.0.3 2021-02-26 00:02 UTC

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Last update: 2021-05-26 00:39:50 UTC


Generate a YAML fixture from DataObjects


composer require chrispenny/silverstripe-data-object-to-fixture

Purpose (early stage)

The purpose of this module (at this early stage) is not to create perfect fixtures, but more to provide a solid guideline for what your fixture should look like.

For example: Writing unit test fixtures can be difficult, especially when you're needing to visualise the structure and relationships of many different DataObjects (and then add an extra layer if you're using, say, Fluent).

Purpose (future development)

One goal for the future of this module is for it to work in tandem with the Populate module. I would like to get to a stage where content authors are able to (for example) "export pages" through the CMS, so that those pages can then be recreated via Populate (without a dev needing to create the fixture themselves).


This is in very, very early development stages. Please be aware that:

  • Namespaces might change
  • Classes might change
  • Entire paradigms on how I generate the fixtures might change

What won't change:

  • The public API will not change. There will still be a service with those 3 main methods.

I would not recommend that you use this module (at this stage) for any application critical features, but I would recommend that you use it as a developer tool (to help you write your own fixtures, either for tests, or to be used with Populate).

Dev task

A dev task can be found at /chrispenny/silverstripe-data-object-to-fixture.

This task will allow you to generate a fixture (output on the screen for you to copy/paste) for any DataObject that you have defined in your project.

General usage

// Instantiate the Service.
$service = new FixtureService();

// Fetch the DataObject that you wish to generate a fixture for.
/** @var Page $page */
$page = Page::get()->byID(1);

// Add the DataObject to the Service.

// Check for warnings? This is somewhat important, because if you have looping relationships (which we have no way of
// creating fixtures for at the moment) this is how you'll know about it.
if (count($service->getWarnings()) > 0) {

// Do something with the fixture output.

// Or maybe save the output to a file?
$fixture = Director::baseFolder() . '/app/resources/fixture.yml';
file_put_contents($fixture, $service->outputFixture());

Set a maximum depth to export

If you are having issues with "nesting level of '256' reached", then one option is to set a maximum depth that the Service will attempt to export.

// Instantiate the Service.
$service = new FixtureService();

Excluding classes from export

There might be some classes (like Members?) that you don't want to include in your fixture. The manifest will check classes for the existence (and truth) of the config variable exclude_from_fixture_relationships.

You can set this in a yml file:

  exclude_from_fixture_relationships: 1

  exclude_from_fixture_relationships: 1

  exclude_from_fixture_relationships: 1

  exclude_from_fixture_relationships: 1

The above examples have been set in _config/model.yml. If you wish to override them, you can also do so by adding your own yml config "After" dataobjecttofixturemodel. EG:

Name: my_dataobjecttofixturemodel
After: dataobjecttofixturemodel
  exclude_from_fixture_relationships: 0

Excluding relationships from export

Similar to excluding classes, there might be some specific relationships on specific classes that you want to exclude. Perhaps you have identified a looping relationship, and you would like to exclude one of them to make things predictable, or perhaps it's just a relationship you don't need in your fixtures.

You can exclude specific relationships by adding excluded_fixture_relationships to the desired class.

excluded_fixture_relationships accepts an array of relationship names.


class MyModel extends DataObject
    private static $has_one = [
        'FeatureImage' => Image::class,
    - FeatureImage

Common issues

Relationship to ElementalArea missing

TL;DR: There is a looping relationship between Page and ElementalArea in later versions of Elemental. You can exclude the has_one on ElementalArea as follows.

    - TopPage

Extra info: Issue.

Nesting level of '256' reached

Above are three options that you can use to attempt to reduce this.

I would recommend that you begin by exluding classes that you don't need for your export, then move to excluding specific relationships that might be causing deep levels of nested relationships, and finally, if those fail, you can set a max depth.

DataObject::get() cannot query non-subclass DataObject directly

You might see this error if you have a relationship being defined as simply DataObject::class, EG:

private static $has_one = [
    'Parent' => DataObject::class,

This module needs to know what DataObject it is querying for. Modules like Userforms do this because you can technically have any Model as the parent. These modules do, however, store the class name for this relationship in a separate field so that we are able to query for the parent appropriately. For Userforms, the class name for this relationship is stored in a field called ParentClass. This module doesn't know that though.

You can tell this module where that class name information lives for any relationship by using the following configuration (this is using Userforms as the example):

    ParentID: ParentClass

field_classname_map is the config we want to populate, and it expects an array with the relationship field name as the key, and the corresponding class name field as the value.

The module uses relField() with the value, so you could be presenting this information through a data field, or a method.

Supported relationships

  • has_one
  • has_many
  • many_many where a through relationship has been defined.

Unsupported relationships

  • many_many where no through relationship has been defined (you should be using through.... Use through).
  • has_one relationships that result in a loop of relationships (belongs_to is the "backward" definition for a has_one relationship, unfortunately, this is not currently supported in fixtures, so, we have no way to create a fixture for relationships that loop).

Fluent support

It is my intention to support Fluent and exporting Localised fields.

Current state does support this, but, again, this is still very early development, so you should be validating everything before you just go right ahead and assume it's perfect.

Future features

  • Add the option/ability to store binary files so that they can be restored with the fixture.
  • Let me know what else you'd like!

Things that this module does not currently do

  • Export _Live tables. I hope to add _Live table exports soon(ish).
  • There is no ordering logic for records within the same class. This means that if you have classes that can have relationships to itself, the order or records might not be correct.
  • Support for exporting/saving away Asset binary files has not been added. This means that in the current state, you can only generate the database record for an Asset.