Upgrading a module to be compatible with Silverstripe CMS 4

This guide will help you upgrade a Silverstripe CMS 3 module to be compatible with Silverstripe CMS 4.

You should be familiar with Upgrading a project to Silverstripe CMS 4 before reading this guide. The process for upgrading a Silverstripe CMS module is very similar to the process for Upgrading a Silverstripe CMS project. This guide focuses on highlighting ways in which upgrading a module differs from upgrading a regular project.

Improving the upgrade experience of your users with a ".upgrade.yml" file

Making your module compatible with Silverstripe CMS 4 is only one part of the process. As a module maintainer, you also want to provide a good upgrade experience for your users. Your module can integrate with the Silverstripe CMS upgrader just like the Silverstripe CMS core modules.

Your Silverstripe CMS 4 module should ship with a .upgrade.yml file. This file is read by the upgrader and will define new APIs introduced by the upgraded version of your module. Each step in this guide details what entry you should add to your module's .upgrade.yml file.

Step 0 - Branching off your project

You'll want to run your module upgrade on a dedicated development branch. While it's possible to upgrade a module from within a Silverstripe CMS project, it's usually cleaner and easier to clone your module and work directly on it.

# We're assumming that the default branch of you module is the latest SS3 compatible branch 
git clone git@github.com:example-user/silverstripe-example-module.git
cd silverstripe-example-module

git checkout -b pulls/ss4-upgrade
git push origin pulls/ss4-upgrade --set-upstream

If you're planning to keep supporting the Silverstripe CMS 3 version of your module, consider creating a dedicated Silverstripe CMS 3 branch.

To require the development branch of your module in a Silverstripe CMS 4 project, you can use composer and prefix the name the name of your branch with dev-.

composer require example-user/silverstripe-example-module dev-pulls/ss4-upgrade

If the development branch is hosted on a different Git remote than the one used to publish your module, you'll need to add a VCS entry to your test project's composer.json file.

  "name": "example-user/test-project",
  "type": "project",
  "require": {
    "example-user/silverstripe-example-module": "dev-pulls/ss4-upgrade"
  "repositories": [
      "type": "vcs",
      "url": "git@github.com:alternative-user/silverstripe-example-module.git"

You will not be able to install your development branch in a Silverstripe CMS 4 project until you've adjusted your module's dependencies.

Step 1 - Upgrade your dependencies

Before you can install your module in a Silverstripe CMS 4 project, you must update your module's composer.json file to require Silverstripe CMS 4 compatible dependencies. In most cases, you'll be better off updating your module's composer file manually, especially if your module only requires a small number of dependencies. You can use upgrader's recompose command if you want, but you'll need to carefully validate the resulting composer.json file.

Update module's type

Silverstripe CMS 4 modules are now installed inside the vendor directory. To get your module installed in the vendor directory, you'll need to update its type to silverstripe-vendormodule. You'll also need to add a dependency to silverstripe/vendor-plugin.

    "name": "example-user/silverstripe-example-module",
-    "type": "silverstripe-module",
+    "type": "silverstripe-vendormodule",
    "require": {
+        "silverstripe/vendor-plugin": "^1",
+        "silverstripe/framework": "^3"


Prefer specific modules over recipes

When upgrading a project, it is recommended to require recipes rather than modules. However, when upgrading a module, you want to limit the number of additional packages that gets installed along with your module. You should target specific packages that your module depends on.

For example, let's say your module adds a ModelAdmin to the Silverstripe CMS administration area without interacting with the CMS directly. In this scenario, the main module you need is silverstripe/admin which contains the ModelAdmin class and related administration functionality. If you update your composer.json file to require silverstripe/recipe-cms, you'll force your users to install a lot of modules they may not need like silverstripe/cms, silverstripe/campaign-admin, silverstripe/asset-admin, silverstripe/versioned-admin.

Avoid rigid constraints

Choose constraints based on the minimum version of Silverstripe CMS 4 you are planning on supporting and allow your module to work with future releases.

For example, if your module requires an API that got introduced with the 4.1 release of silverstripe/framework, then that's the version you should target. You should use the caret symbol (^) over the tilde (~) so your module works with more recent releases. In this scenario, your constraint should look like "silverstripe/framework": "^4.1".

Avoid tracking unnecessary files

If you run composer commands from your module's folder, a lock file will be created and dependencies will be installed in a vendor folder. You may also get project-files and public-files entries added under the extra key in your composer.json.

While these changes may be useful for testing, they should not be part of the final release of your module.

Finalising the module's dependency upgrade

You should commit the changes to your module's composer.json and push them to your remote branch.

By this point, your module should be installable in a test Silverstripe CMS 4 project. It will be installed under the vendor directory (e.g.: vendor/example-user/silverstripe-example-module). However, it will throw exceptions if you try to run it.

From this point, you can either work from a test project or you can keep working directly on your module.

Step 2 - Update your environment configuration

As a module maintainer, you shouldn't be shipping any environment file with your module. So there's no need for you to run the upgrader environment command. If your module requires environment variables, you should update your documentation accordingly, but otherwise you can move on to the next step.

Step 3 - Namespacing your module

Namespacing your module is mandatory to get it working with Silverstripe CMS 4. You can use the add-namespace upgrader command to achieve this.

# If you are working from a test project, you need to specify the `--root-dir` parameter
upgrade add-namespace --root-dir vendor/example-user/silverstripe-example-module \
  "ExampleUser\\SilverstripeExampleModule" \
# If you are working directly from the module, you can ommit `--root-dir` parameter
upgrade add-namespace "ExampleUser\\SilverstripeExampleModule" code/

If your module codebase is structured in folders, you can use the --psr4 and --recursive flag to quickly namespace your entire module in one command. This command will recursively go through the code directory and namespace all files based on their position relative to code.

upgrade add-namespace --recursive --psr4 "ExampleUser\\SilverstripeExampleModule" code/

Configuring autoloading

You need to update your composer.json file with an autoload entry, so composer knows what folder maps to what namespace.

You can do this manually:

    "name": "example-user/silverstripe-example-module",
    "type": "silverstripe-vendormodule",
    "require": {
        "silverstripe/framework": "^4",
        "silverstripe/vendor-plugin": "^1"
-    }
+    },
+    "autoload": {
+        "psr-4": {
+            "ExampleUser\\SilverstripeExampleModule\\": "code/",
+            "ExampleUser\\SilverstripeExampleModule\\Tests\\": "tests/"
+        }
+    }

Alternatively, you can use the --autoload parameter when calling add-namespace to do this for you.

upgrade add-namespace --recursive --psr4 --autoload "ExampleUser\\SilverstripeExampleModule" code/
upgrade add-namespace --recursive --psr4 --autoload "ExampleUser\\SilverstripeExampleModule\\Tests" tests

Learn more about configuring autoloading in your composer.json file.

Preparing your

add-namespace will create a .upgrade.yml file that maps your old class names to their new namespaced equivalent. This will be used by the upgrade command in the next step.

Depending on the nature of your module, you may have some class names that map to other common names. When the upgrade command runs, it will try to substitute any occurrence of the old name with the namespaced one. This can lead to accidental substitution. For example, let's say you have a Link class in your module. In many project the word Link will be used for other purposes like a field label or property names. You can manually update your .upgrade.yml file to define a renameWarnings section. This will prompt users upgrading to confirm each substitution.

  # Prompt user before replacing references to Link
  Link: ExampleUser\SilverstripeExampleModule\Model\Link
  # No prompt when replacing references to ExampleModuleController
  ExampleModuleController: ExampleUser\SilverstripeExampleModule\Controller
  - Link

Make sure to commit this file and to ship it along with your upgraded module. This will allow your users to update references to your module's classes if they use the upgrader on their project.

Finalising your namespaced module

By this point:

  • all your classes should be inside a namespace
  • your composer.json file should have an autoload definition
  • you should have a .upgrade.yml file.

However, your codebase is still referencing Silverstripe CMS classes by their old non-namespaced names. Commit your changes before proceeding to the next step.

Step 4 - Update codebase with references to newly namespaced classes

This part of the process is identical for both module upgrades and project upgrades.

# If upgrading from inside a test project
upgrade-code upgrade --root-dir vendor/example-user/silverstripe-example-module \
# If upgrading the module directly
upgrade-code upgrade ./

All references to the old class names will be replaced with namespaced class names.

By this point, you should be able to load your module with PHP. However, your module will be using deprecated APIs.

Step 5 - Updating your codebase to use Silverstripe CMS 4 API

This step will allow you to update references to deprecated APIs. If you are planning on making changes to your own module's API, take a minute to define those changes in your .upgrade.yml:

  • this will help you with updating your own codebase
  • your users will be warned when using your module's deprecated APIs.

You can define warnings for deprecated APIs along with a message. If there's a one-to-one equivalent for the deprecated API, you can also define a replacement. e.g.:

      message: 'This warning message will be displayed to your users'
      url: 'https://github.com/example-users/silverstripe-example-module/en/4/changelogs/#object-replace'
      message: 'Replace with a different method'
      replacement: 'newBetterMethod'
      message: 'Replace with a different property'
      replacement: 'newProperty'

When you are done updating your .upgrade.yml file, you can run the inspect command to search for deprecated APIs.

# If upgrading from inside a test project
upgrade-code inspect --root-dir vendor/example-user/silverstripe-example-module \
# If upgrading the module directly
upgrade-code inspect code/

Step 6 - Update your entry point

Module do not have an entry point. So there's nothing to do here.

Step 7 - Update project structure

This step is optional. We recommend renaming code to src. This is only a convention and will not affect how your module will be executed.

If you do rename this directory, do not forget to update your autoload configuration in your composer.json file.

Step 8 - Switch to public web-root

The public web root does not directly affect module. So you can skip this step.

Step 9 - Move away from hardcoded paths for referencing static assets

While Silverstripe CMS 4 projects can get away with directly referencing static assets under some conditions, modules must dynamically expose their static assets. This is necessary to move modules to the vendor folder and to enable the public web root.

Exposing your module's static assets

You'll need to update your module's composer.json file with an extra.expose key.

    "name": "example-user/silverstripe-example-module",
    "type": "silverstripe-vendormodule",
    "require": {
        "silverstripe/framework": "^4",
        "silverstripe/vendor-plugin": "^1"
    "autoload": {
        "psr-4": {
            "ExampleUser\\SilverstripeExampleModule\\": "code/"
    "autoload-dev": {
        "psr-4": {
            "ExampleUser\\SilverstripeExampleModule\\Tests\\": "tests/"
-    }
+    },
+    "extra": {
+        "expose": [
+            "images",
+            "styles",
+            "javascript"
+        ]
+    }

Referencing static assets

This process is essentially the same for projects and modules. The only difference is that module static asset paths must be prefix with the module's name as defined in their composer.json file.

- Requirements::css('silverstripe-example-module/styles/admin.css');
+ Requirements::css('example-user/silverstripe-example-module: styles/admin.css');
$pathToImage =
-    'silverstripe-example-module/images/logo.png';
+    ModuleResourceLoader::singleton()->resolveURL('example-user/silverstripe-example-module: images/logo.png');

Step 10 - Update database class references

Just like projects, your module must define class names remapping for every DataObject child.

    ExampleModuleDummyDataObject: ExampleUser\SilverstripeExampleModule\Models\DummyDataObject

On the first dev/build after a successful upgrade, the ClassName field on each DataObject table will be substituted with the namespaced classname.

Extra steps

You've been through all the steps covered in the regular project upgrade guide. These 2 additional steps might not be necessary.

Create migration tasks

Depending on the nature of your module, you might need to perform additional tasks to complete the upgrade process. For example, the framework module ships with a file migration task that converts files from the old Silverstripe CMS 3 structure to the new structure required by Silverstripe CMS 4.

Extend BuildTasks and create your own migration task if your module requires post-upgrade work. Document this clearly for your users so they know they need to run the task after they're done upgrading their project.

Keep updating your

The upgrader can be run on projects that have already been upgraded to Silverstripe CMS 4. As you introduce new API and deprecate old ones, you can keep updating your .upgrade.yml file to make it easy for your users to keep their code up to date. If you do another major release of your module aimed at Silverstripe CMS 4, you can use all the tools in the upgrader to make the upgrade process seamless for your users.