feat: add mutator support for generic classes

[simonresch]

Adds mutator support for generic classes.

Constructing mutators for generic classes would previously either fail or not work as expected due to parameter and return types being reported as java.lang.Object by the reflection API (type erasure). Since we can't provide a general Object mutator this would creation of a valid mutator for most generic classes.
Using the AnnotatedType of the class we resolve type parameters to create the correct underlying mutators.

Example fuzz test:

  public static class MyClass<L, S> {
    private final L[] list;
    private final Set<S> set;

    public MyClass(L[] list, Set<S> set) {
      this.list = list;
      this.set = set;
    }

    public L[] getList() {
      return this.list;
    }

    public Set<S> getSet() {
      return this.set;
    }
  }

  @FuzzTest
  void fuzzTest(@NotNull(constraint = PropertyConstraint.RECURSIVE) MyClass<String, Integer> data) {
    if (data.getList().length > 5
        && data.getList()[5].equals("foo")
        && data.getSet().size() == 5) {
      throw new RuntimeException("Can fuzz generics");
    }
  }

[Copilot]

Pull Request Overview

This PR adds support for generic classes in the mutator framework by resolving type parameters at runtime. Previously, generic classes would fail to create valid mutators due to type erasure causing parameter and return types to be reported as java.lang.Object. The implementation uses AnnotatedType to resolve type parameters and construct mutators with the correct concrete types.

Key Changes:

• Added type resolution logic to handle generic type parameters in constructors, methods, and return types
• Updated all aggregate mutator factories to resolve generic types before creating mutators
• Added comprehensive test coverage for generic classes across different mutator types (setter-based, constructor-based, cached, records)

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
BeanSupport.java	Adds core type resolution methods for resolving generic type arguments in methods, constructors, and return types
AggregatesHelper.java	Updates mutator creation to use resolved types instead of raw types from reflection API
CachedConstructorMutatorFactory.java	Uses resolved parameter types when building mutators for generic classes
ConstructorBasedBeanMutatorFactory.java	Resolves parameter types and return types when matching getters to constructors
SetterBasedBeanMutatorFactory.java	Resolves setter parameter types to properly handle generic classes
SuperBuilderMutatorFactory.java	Updates to use resolved parameter types for builder pattern support
SetterBasedBeanMutatorTest.java	Adds test for generic class with setter-based mutation
RecordMutatorTest.java	Adds test for generic record types
ConstructorBasedBeanMutatorTest.java	Adds tests for generic classes with single and nested type parameters
CachedConstructorMutatorTest.java	Adds test for generic class with cached constructor
StressTest.java	Adds stress test cases for various generic class patterns

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[simonresch]

Added a commit to support non-trivial use of the type variable. For example the fuzz test

  public static class MyClass<L, S> {
    private final L[] list;
    private final Set<S> set;

    public MyClass(L[] list, Set<S> set) {
      this.list = list;
      this.set = set;
    }

    public L[] getList() {
      return this.list;
    }

    public Set<S> getSet() {
      return this.set;
    }
  }

  @FuzzTest
  void fuzzTest(@NotNull(constraint = PropertyConstraint.RECURSIVE) MyClass<String, Integer> data) {
    if (data.getList().length > 5
        && data.getList()[5].equals("foo")
        && data.getSet().size() == 5) {
      throw new RuntimeException("Can fuzz generics");
    }
  }

will create a mutator like this: Arguments[[String[], Set<Integer>] -> MyClass]

[Copilot]

Pull Request Overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

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[oetr]

Awesome, thanks!

The type resolution doesn't work for some cases, but other than that it looks solid. Great work!

[oetr]

Great work!

Just some small final issues from my side.