Allow Transitive Dependencies

[1ma]

Problem

deptrac only allows explicit dependencies listed in the ruleset and sometimes the list can get quite unwieldly, especially when there's lots of layers (e.g. a DDD project with 3 layers per bounded context and upstream relations). In these situations it would be handy if deptrac allowed transitive dependencies (IOW if B can depend on A and C can depend on B then C should be able to depend on A, too).

Since this would be a breaking change it could be implemented as a command flag (something like --allow-transitive-deps). Thoughts?

Example

paths:
  - ./src

layers:
  - name: Domain
    collectors:
      - type: className
        regex: ^Domain\\.*
  - name: Application
    collectors:
      - type: className
        regex: ^Application\\.*
  - name: Infrastructure
    collectors:
      - type: className
        regex: ^Infrastructure\\.*

ruleset:
  Domain:
  Application:
    - Domain
  Infrastructure:
    - Application

// src/Infrastructure/Controller.php

namespace Infrastructure;

class Controller
{
    public function __invoke()
    {
        new \Domain\Entity();
    }
}

$ php vendor/bin/deptrac 

deptrac is alpha, not production ready.
please help us and report feedback / bugs.

Start to create an AstMap for 3 Files.
...
AstMap created.
start emitting dependencies "InheritanceDependencyEmitter"
start emitting dependencies "BasicDependencyEmitter"
end emitting dependencies
start flatten dependencies
end flatten dependencies
collecting violations.
formatting dependencies.
Infrastructure\Controller::11 must not depend on Domain\Entity (Infrastructure on Domain)

Found 1 Violations

Desired output:

$ php vendor/bin/deptrac 

deptrac is alpha, not production ready.
please help us and report feedback / bugs.

Start to create an AstMap for 3 Files.
...
AstMap created.
start emitting dependencies "InheritanceDependencyEmitter"
start emitting dependencies "BasicDependencyEmitter"
end emitting dependencies
start flatten dependencies
end flatten dependencies
collecting violations.
formatting dependencies.

Found 0 Violations

PS related, but vague-r issue: #158

[josefsabl]

It could be useful for some architectures. I think this would, however, be better if you could specify this in the ruleset, not as a global flag. Parts of your system may have different rules.

[MartinMystikJonas]

Maybe this could be somehow specified in rules. Like "Application" means only Application and "+Application" means Application plus all layers Application can depend on.

[smoench]

I would be fine with this notation. Does anyone want to provide a PR?