Avoid uncompilable output when migrating JobBuilderFactory/StepBuilderFactory

[steve-aom-elliott]

Problem

When a class injects JobBuilderFactory or StepBuilderFactory via a multi-arg constructor, or exposes the factory through accessor methods, the current recipes produce uncompilable code:

• The field is deleted while getters, setters, and helper methods still reference it.

• MigrateJobBuilderFactory already has a constructor carve-out that drops the JobBuilderFactory parameter, but the matching this.<field> = <param>; body assignment is left behind — orphaning both sides after field deletion.

• MigrateStepBuilderFactory has no constructor carve-out, so the StepBuilderFactory parameter survives even when the rest of the file has been migrated, leaving a reference to a class that no longer exists in Spring Batch 5.

• This affects classes that follow the standard Spring constructor-injection pattern — exactly the shape called out in Deprecated StepBuilderFactory/JobBuilderFactory types left alone when it's not used in same Java file #788 and Migration to Spring Batch 5.2 : StepBuilderFactory/JobBuilderFactory partially migrated when used as constructor arguments #789.

Changes

Field deletion is now usage-aware (both recipes). Before deleting a JobBuilderFactory/StepBuilderFactory field, each visitor scans the class for type-aware references to the field outside the methods it will rewrite (constructors and methods containing .get(...)). The check uses J.Identifier.getFieldType() and confirms the declaring type matches the enclosing class, so local variables and parameters that happen to share the field's simple name are not false positives. If outside references exist (getters, setters, helper methods), the field is preserved and constructor parameter removal is skipped — the field, parameter, and body assignment remain wired up for the developer to clean up.

Constructor body cleanup moves in lockstep with parameter removal (both recipes). When a JobBuilderFactory/StepBuilderFactory parameter is dropped from a method declaration, any matching this.<field> = <removedParam>; body assignment is removed rather than being left referencing a parameter that no longer exists.

MigrateStepBuilderFactory gets a constructor carve-out. AddJobRepositoryVisitor.visitMethodDeclaration now rewrites constructors that take a StepBuilderFactory parameter, mirroring the existing behavior in MigrateJobBuilderFactory. Gated by the field-preservation guard above.

Tests

Five new tests across MigrateJobBuilderFactoryTest and MigrateStepBuilderFactoryTest:

• Field preserved when getters/setters reference it; the .get(...) chain still rewrites.

• Constructor body assignment removed when its parameter is removed (no accessors present).

• StepBuilderFactory constructor parameter removed and body assignment cleaned up.

• StepBuilderFactory field preserved when accessor methods reference it.

• Local variable shadowing the field's simple name does not trigger preservation — the tightened type-aware check ignores it.

• Closes Deprecated StepBuilderFactory/JobBuilderFactory types left alone when it's not used in same Java file #788

• Closes Migration to Spring Batch 5.2 : StepBuilderFactory/JobBuilderFactory partially migrated when used as constructor arguments #789