Trunk Based

Development

Fallacies of "safe" development

DevOps*: We don't trust developers, deployment/release should be done by a dedicated team
QA*: We don't trust developers, untested code should not be in "trunk"
Developers: We don't trust other teams, they are going to break our staff

* DevOps here represents "someone who runs deployments" and not the culture it is supposed to represent.
*QA (Quality Assurance) here is more Quality Control

Not only simple git conflicts

Semantic Conflicts
Conflicts within user flow
Conflicts within requirements

CI is...

Everyone merges their work into master daily
Fix Broken Builds Immediately
Everyone can see what's happening

https://trunkbaseddevelopment.com/

Slicing large work into a bunch of small changes is more work.
The need to slice work into smaller chunks means unfinished features in trunk
There's a fear that changes could break production since "story" for related code is not "tested".

Challenges

Spike Solution

Try and throw away implementation

How to deal with unfinished work?

Feature flags/toggles
Branch by abstraction

Feature Flags

In essence, replace VCS branches with conditional branches in the code

if (myNewCoolFeatureEnabled) {
   return <MyNewCoolComponent some={props} />
}

Many More

Common mistakes with Feature Flags

Feature Flag Reuse
Unclear Feature Flag Names/Description
Not managing your feature flags

Branch by Abstraction

class MyServiceSwitcher implements MyService
{
  	public function __construct(
		private MyServiceOldImplementation $old,
		private MyServiceImplementation $new,
		private FeatureFlags $featureFlags
  	) {}
  
	public function doSomething()
  	{
		$isEnabled = $this->featureFlags->isEnabled('relace_some_service')
		if ($isEnabled) {
			return $this->new->doSomething();
		}
		return $this->old->doSomething();
	}
}