Slides from StripeCon15 - London, 16th October 2015

1. Why you shouldn’t
edit SilverStripe
core files
(and how to do it anyway)
By Loz Calver / @kinglozzer

2. What do you mean “editing
core files”?
Modifying someone else’s code
Code outside the scope of “your project”
Applies to framework, cms and any other modules

3. Why would I edit core files?
Bugs - SilverStripe isn’t (quite) perfect
Security
need urgent/immediate fix
email us!
Missing/upcoming features - time delay between minor versions
Clients!
security@silverstripe.org

4. Why shouldn’t I edit core files?
Other developers don’t know what you’ve done
Updates are harder
(you should all be keeping up to date!)
eventually you’ll get bored or frustrated and give up
You might accidentally introduce other issues

5. How can I avoid editing core?

6. Workaround 1: Extensions
Example 1: adding database fields & extra methods
MyMemberExtension.php
<?php
class MyMemberExtension extends DataExtension {
private static $db = array(
'DateOfBirth' => 'SS_Datetime'
);
public function SayHi() {
return "Hi " . $this->owner->Name;
}
}
_config.yml
Member:
extensions:
- MyMemberExtension

7. Workaround 1: Extensions
Example 2: augmenting database queries
BlogPostFilter.php
<?php
class BlogPostFilter extends DataExtension {
public function augmentSQL(SQLQuery &$query) {
$stage = Versioned::current_stage();
if ($stage == 'Live' || !Permission::check('VIEW_DRAFT_CONTENT')) {
$sqlNow = Convert::raw2sql(SS_Datetime::now());
$query->addWhere(sprintf('"PublishDate" < '%s'', $sqlNow));
}
}
}
_config.yml
BlogPost:
extensions:
- BlogPostFilter

8. Workaround 1: Extensions
Pros
Can be used to add things to built-in classes
Reusable: package them up, release them as modules!
Cons/Caveats
Reliant on extension points
Extensions have limited power

9. Workaround 2: Injector
Example: adding an extension hook
ManyManyListWithHook.php
<?php
class ManyManyListWithHook extends ManyManyList {
public function add($item, $extraFields = null) {
parent::add($item, $extraFields);
if($item instanceof DataObject) {
$item->extend('onAfterManyManyAdd', $this);
}
}
}
_config.yml
Injector:
ManyManyList:
class: ManyManyListWithHook

10. Credit to / module@camspiers silverstripe-cacheinclude

11. Workaround 2: Injector
Example: using the extension hook
MemberExtension.php
<?php
class MemberExtension extends Extension {
public function onAfterManyManyAdd(ManyManyList $list) {
Debug::log('Member added to many_many relation');
}
}
_config.yml
Member:
extensions:
- MemberExtension

12. Workaround 2: Injector
Pros
Can “replace” an entire class
Super powerful
Cons/Caveats
With great power comes great responsibility
Must be instantiated with one of:
Class::create()
Injector::inst()->get('Class')
Injector::inst()->create('Class')
Injector::inst()->createWithArgs('Class')

14. When all else fails, fork it!
Create a fork, apply your fix
Use Git to periodically rebase from “upstream”
Composer helps to make this easier!

15. Example
composer.json
{
"require": {
"silverstripe/cms": "3.1.15",
"silverstripe/framework": "3.1.15"
},
"repositories": [
{
"type": "vcs",
"url": "git@github.com:kinglozzer/sapphire.git"
}
]
}

16. Example
composer.json
{
"require": {
"silverstripe/cms": "3.1.15",
"silverstripe/framework": "dev-hotfix"
},
"repositories": [
{
"type": "vcs",
"url": "git@github.com:kinglozzer/sapphire.git"
}
]
}

17. Not quite...

18. Fixed!
composer.json
{
"require": {
"silverstripe/cms": "3.1.15",
"silverstripe/framework": "dev-hotfix"
},
"repositories": [
{
"type": "vcs",
"url": "git@github.com:kinglozzer/sapphire.git"
}
]
}

19. Fixed!
composer.json
{
"require": {
"silverstripe/cms": "3.1.15",
"silverstripe/framework": "dev-hotfix as 3.1.15"
},
"repositories": [
{
"type": "vcs",
"url": "git@github.com:kinglozzer/sapphire.git"
}
]
}

20. Forking
Pros
Easier to:
keep track of modifications made
re-apply changes during updates - rebase/cherry-pick
create a PR!
Cons/Caveats
While easier, it’s still extra effort!
Slows down composer updates

21. Summary
Use extensions where possible
For simple additions/fixes to methods, Injector should be okay
For anything else you can’t work around, fork as last resort
Use Composer!

22. Thanks/questions
Feedback welcomed!
@kinglozzer @kinglozzer lozcalver@bigfork.co.uk