Scaffolding fails for a self-referencing many-to-many join table when both FKs yield the same navigation name

[ilkertskn]

• The name generated for the left skip navigation was neither added to the existing identifiers nor present in the model when the right name was generated, and the identifier list is shared by both ends when the join table references a single entity type, so the uniquifier produced the same name twice and AddSkipNavigation threw, failing the whole scaffolding operation
• Add the generated name to the identifiers so the right-hand side sees it
• Add a test for a self-referencing join table whose foreign keys yield the same candidate name

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        Fixes #bugnumber

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[ilkertskn]

@dotnet-policy-service agree

[Copilot]

Pull request overview

Fixes a reverse-engineering/scaffolding failure for self-referencing many-to-many join tables where both skip navigations end up with the same generated name, causing AddSkipNavigation to throw and scaffolding to fail.

Changes:

• Ensures the left skip-navigation name is added to the existing identifier set before generating the right skip-navigation name (preventing duplicate-name generation in self-referencing join scenarios).
• Adds a new regression test intended to cover colliding skip-navigation names on a self-referencing join table.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/EFCore.Design/Scaffolding/Internal/RelationalScaffoldingModelFactory.cs	Makes the left skip-navigation name visible to subsequent naming to avoid collisions when both ends share the same identifier list.
test/EFCore.Design.Tests/Scaffolding/Internal/RelationalScaffoldingModelFactoryTest.cs	Adds a regression test for self-referencing many-to-many join-table skip-navigation name collisions.

Suppressed comments (1)

test/EFCore.Design.Tests/Scaffolding/Internal/RelationalScaffoldingModelFactoryTest.cs:2734

• The assertions only check for uniqueness, which could still pass if the candidate names don’t collide (or if the uniquifier changes behavior). Tightening this to assert the expected collision resolution (e.g. Products and ProductsNavigation) makes the regression coverage more direct and stable.

        Assert.Equal(2, skipNavigationNames.Count);
        Assert.Equal(skipNavigationNames.Count, skipNavigationNames.Distinct().Count());

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