Deprecating code#

Needs of developers (both on core framework and custom projects) can outgrow the capabilities of a certain API. Existing APIs might turn out to be hard to understand, maintain, test or stabilise. In these cases, it is best practice to "refactor" these APIs into something more useful.

Sometimes refactoring API means we rename or entirely remove classes and methods in a major release. To make upgrading to that release easier, deprecation warnings should be provided so developers know what is going to be removed and how they need to update their code.

Deprecating API best practice#

• Add a @deprecated item to the docblock tag, with the version when the code was deprecated and a message indicating what to use instead.
• Update the deprecated code to throw a Deprecation::notice() warning.
• Both the docblock and error message should contain the version where the functionality is deprecated from. So, if you're committing the change to a 4.12 minor release, the version will be 4.12.0.
• Make sure that the old deprecated method works by calling the new function where possible - avoid duplicated code.
• Deprecated APIs can be removed only after developers have had sufficient time to react to the changes. Hence, deprecated APIs should be removed in major releases only. Between major releases, leave the code in place with a deprecation warning.

When deprecating a method:

• Add the following docblock @deprecated 1.2.3 Use anotherMethod() instead
• Deprecation::notice('1.2.3', 'Use anotherMethod() instead'); to the top of the method
• Wrap Deprecation::notice() with Deprecation::withSuppressedNotice() if there's no replacement for that deprecated method and it's not feasible to wrap all calls to the method

When deprecating a class:

• Add the following docblock @deprecated 1.2.3 Use AnotherClass instead
• Add Deprecation::notice('1.2.3', 'Use AnotherClass instead', Deprecation::SCOPE_CLASS); to the top of __construct()

• Wrap Deprecation::notice() with Deprecation::withSuppressedNotice() if there's no replacement for that deprecated class and it's not feasible to wrap all instantiations of the class

  namespace App;
  
  /**
   * @deprecated 4.12.0 Will be removed without equivalent functionality
   */
  class MyDeprecatedClass extends AnotherClass
  {
      public function __construct()
      {
          Deprecation::withSuppressedNotice(function () {
              Deprecation::notice(
                  '4.12.0',
                  'Will be removed without equivalent functionality',
                  Deprecation::SCOPE_CLASS
              );
          });
          parent::__construct();
      }
  }

When deprecating config:

• Add the following docblock @deprecated 1.2.3 Use different_config instead

When deprecating some behaviour, combination of configuration values, parameters, etc:

• Add Deprecation::notice('1.2.3', 'Using x with y is deprecated. Do [other thing] instead', Deprecation::SCOPE_GLOBAL);
• It may not be immediately clear where this type of deprecation warning should go. In that case, add it to the HTTPApplication::warnAboutDeprecatedSetups() method.
• It may be appropriate to link to some documentation in the message for this type of deprecation warning.

In all cases if the replacement method or configuration property exists in another class, or you're replacing one class with another, refer to the replacement using its fully qualified class name.

Avoiding deprecated API#

Wherever possible, once some API has been deprecated, we should stop using it. This allows projects to emit deprecation warnings and have an accurate list of code that they need to change.

In some cases, we may not yet have a replacement for code that is required for the current major - but that we still have to call and support internally. In these cases, since we can't stop calling the code, wrap the call to the deprecated code in Deprecation::withSuppressedNotice() e.g:

use SilverStripe\Dev\Deprecation;

// ...

// The $myVariable variable will get the result of the call to the deprecated $obj->myDeprecatedMethod()
$myVariable = Deprecation::withSuppressedNotice(function () {
    return $obj->myDeprecatedMethod();
});

For any unit tests using the deprecated method/class/config, add the following the the top of the unit test. This ensures that deprecated code is still supported as usual when Deprecation warnings are not enabled, though the tests are skipped whenever you are testing to see if deprecated code is still be called.

namespace SilverStripe\Test;

use SilverStripe\Dev\Deprecation;
use SilverStripe\Dev\SapphireTest;

class MyTest extends SapphireTest
{
    public function testSomething()
    {
        if (Deprecation::isEnabled()) {
            $this->markTestSkipped('Test calls deprecated code');
        }
        // ...
    }
}

Here's an example for replacing Director::isDev() with a (theoretical) SilverStripe\Core\Env::is_dev():

namespace SilverStripe\Control;

use SilverStripe\Dev\Deprecation;
// ...

class Director
{
    // ...

    /**
     * Returns true if your are in development mode
     * @deprecated 4.12.0 Use SilverStripe\Core\Env::is_dev() instead.
     */
    public function isDev()
    {
        Deprecation::notice('4.12.0', 'Use SilverStripe\Core\Env::is_dev() instead');
        return Env::is_dev();
    }
}

This change could be committed to a minor release like 4.12.0, and remains deprecated in all subsequent minor releases (e.g. 4.13.0), until a new major release (e.g. 5.0.0), at which point it gets removed from the codebase.

Enabling deprecation warnings#

Deprecation warnings aren't enabled by default. They can be turned on for dev environments with one of the following methods:

.env

SS_DEPRECATION_ENABLED=true

// app/_config.php
use SilverStripe\Dev\Deprecation;

Deprecation::enable();

To test that deprecated code is no longer being called, run code via CI in an installer/kitchen-sink project that has deprecations enabled. Then view the CI output in the "Run tests" of the GitHub actions CI job and/or view the contents of silverstripe.log in the GitHub actions CI artifact to see if there are deprecation warnings. There should be zero deprecation warnings.

See upgrading - deprecations for more details about enabling deprecation warnings.