Fix issue where copy/paste + delete of original association causes association ends to be removed

[amolenaar]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Documentation content changes

What is the current behavior?

Create a class, connect both ends of an association to it. Copy + paste the association and remove the original.

See tests/test_multiple_associations.py for a failing scenario.

What is the new behavior?

I hope it will work as expected: association ends remain in tact as well as the navigability.

Does this PR introduce a breaking change?

• Yes
• No

Notes

This is also applicable for Connectors!

Scenario's I can think of:

• Class and association are pasted in a new diagram
• Class and association are pasted in a new diagram and original association is deleted
• Class and association are pasted in a new diagram and new association is deleted
• Association is pasted in a new diagram and reconnected to the class (same subject as original)
• Association is pasted and directly deleted
• Class and association are pasted in a new diagram and one end is connected to a different class

What's the behavior we're looking for?

• If an association has >1 presentations, it can only connect to those same types ()
• If an association has ==1 presentations, it can reconnect to another type, association is updated

[danyeaw]

These changes look great, nice simplifications as well and moves us a step closer to full pytest. I just had a nitpick about spelling and a question.

[danyeaw]

I'm sure this is my misunderstanding, if the original a is deleted, I would think that the copy of a called aa is also deleted. Why would these assert statements pass?

[amolenaar]

a is an AssociationItem, aa is also an AssociationItem. Both point to the same association (the subject). If I remove one, the model should not change, since there's still a presentation of the Association model element in a diagram.

[danyeaw]

Thanks for the explanation 👍

[sourcery-ai]

Sourcery Code Quality Report (beta)

✅  Merging this PR will increase code quality in the affected files by 0.03 out of 10.

Quality metrics	Before	After	Change
Complexity	1.40	1.52	0.12 🔴
Method Length	54.86	52.56	-2.30 🔵
Quality	8.63	8.66	0.03 🔵

Other metrics	Before	After	Change
Lines	1517	1480	-37

Changed files	Quality Before	Quality After	Quality Change
gaphor/UML/classes/association.py	8.71	8.76	0.05 🔵
gaphor/UML/classes/classconnect.py	8.47	8.48	0.01 🔵
gaphor/UML/classes/classespropertypages.py	8.88	8.85	-0.03 🔴
gaphor/UML/classes/tests/test_association.py	8.45	8.63	0.18 🔵
gaphor/UML/classes/tests/test_classconnect.py	7.97	7.94	-0.03 🔴

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Overall	Recommendation
gaphor/UML/classes/association.py	AssociationEnd.post_update	17	351.75	3.65	Split out functionality
gaphor/UML/classes/association.py	AssociationItem.post_update	17	183.87	4.73	Split out functionality
gaphor/UML/classes/classespropertypages.py	AssociationPropertyPage.construct	9	196.75	5.34	Split out functionality
gaphor/UML/classes/classespropertypages.py	OperationsPage.construct	6	168.76	5.96	Split out functionality
gaphor/UML/classes/classespropertypages.py	AttributesPage.construct	6	154.80	6.16	Split out functionality

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Let us know what you think of it by mentioning @sourcery-ai in a comment.