Refactor pyerverse Association Logic

[Julfried]

Type of Changes

	Type
✓	🐛 Bug fix
✓	🔨 Refactoring

Description

Closes #9045

Summary

Fixed incorrect UML semantics in pyreverse for aggregation vs composition relationships. The previous implementation had no explicit CompositionsHandler class and did not differentiate between Aggregation and Composition properly, treating most relationships as aggregation by default.

Problem

Pyreverse previously lacked proper UML relationship semantics. So I would proposes the following distinction for Python class relationships:

fields.py

# Test for https://github.com/pylint-dev/pylint/issues/9045

class P:
    pass

class A:
    x: P  # just type hint, no ownership → Association

class B:
    def __init__(self, x: P):
        self.x = x  # receives object, not created → Aggregation

class C:
    x: P
    def __init__(self, x: P):
        self.x = x  # receives object, not created → Aggregation

class D:
    x: P
    def __init__(self):
        self.x = P()  # creates object → Composition

class E:
    def __init__(self):
        self.x = P()  # creates object → Composition

fields.mmd

classDiagram
  class A {
    x
  }
  class B {
    x
  }
  class C {
    x
  }
  class D {
    x
  }
  class E {
    x
  }
  class P {
  }
  P --> A : x
  P --* D : x
  P --* E : x
  P --o B : x
  P --o C : x

Changes Made

1. Added CompositionsHandler

Created dedicated handler following chain of responsibility pattern:
CompositionsHandler → AggregationsHandler → AssociationsHandler

2. Updated Printers

• Added EdgeType.COMPOSITION enum value
• Updated MermaidJS and PlantUML printers with correct arrows per Mermaid docs
• For the Dot printer I used plain arrows, but I did not manage to find something in the dot language documentation

3. Prevented Duplicate Relationships

Modified extract_relationships() to process relationships by priority and avoid duplicates.

Currently I only made the modifications needed to implement the new Associations Logic. If you like the proposed distinction I would work on making the tests pass :)

[github-actions]

🤖 According to the primer, this change has no effect on the checked open source code. 🤖🎉

This comment was generated for commit d0ea86e