Add Excluding by type with inheritance support #3115

Copilot · 2025-10-18T07:36:52Z

Summary

This PR implements the API proposal from #2390 to add a cleaner, more intuitive way to exclude all members of a certain type from structural equivalency assertions, with full support for inheritance and generic type hierarchies.

Motivation

Previously, to exclude all members of a specific type (e.g., TimeSpan), you had to write verbose predicate expressions:

options.Excluding(mi => mi.Type == typeof(TimeSpan))

For interfaces, the syntax was even more complex:

options.Excluding(mi => typeof(IEnumerable<int>).IsAssignableFrom(mi.Type))

And for open generic types like Nullable<>, it was quite cumbersome:

options.Excluding(mi => mi.Type.IsGenericType && 
                         mi.Type.GetGenericTypeDefinition() == typeof(Nullable<>))

Changes

This PR adds two new methods to SelfReferenceEquivalencyOptions<TSelf>:

1. Generic Method: `Excluding<TMember>()`

subject.Should().BeEquivalentTo(expectation, options => options
    .Excluding<TimeSpan>());

2. Type Parameter Method: `Excluding(Type type)`

subject.Should().BeEquivalentTo(expectation, options => options
    .Excluding(typeof(Nullable<>)));

Features

Type Matching with Inheritance Support

For non-sealed types, the exclusion includes all derived types:

options.Excluding<BaseClass>()  // Excludes BaseClass and all types deriving from it

Sealed Type Matching

For sealed types (like string), only exact matches are excluded:

options.Excluding<string>()  // Excludes only string (sealed type)

Interface and Abstract Type Support

For interfaces and abstract types, all implementing/derived types are excluded:

options.Excluding<IEnumerable<int>>()  // Excludes List<int>, int[], HashSet<int>, etc.

Open Generic Type Matching with Full Inheritance Support

Supports excluding all closed generics and types deriving from them:

options.Excluding(typeof(Nullable<>))        // Excludes int?, double?, DateTime?, etc.
options.Excluding(typeof(OpenGeneric<>))    // Excludes OpenGeneric<int>, DerivedOpenGeneric<T>, etc.

This includes:

Closed generics: class ClosedGeneric : OpenGeneric<int>
Derived open generics: class DerivedOpenGeneric<T> : OpenGeneric<T>
Closed derived generics: class ClosedDerivedGeneric : DerivedOpenGeneric<int>

Multiple Exclusions

Methods can be chained for excluding multiple types:

options.Excluding<TimeSpan>()
       .Excluding<DateTime>()
       .Excluding<double>()

Works at All Nesting Levels

Exclusions apply throughout the entire object graph, including nested objects and collections.

Implementation Details

Added new ExcludeMemberByTypeSelectionRule class that implements IMemberSelectionRule
The rule intelligently handles multiple scenarios:
- Sealed types: Uses exact type equality (memberType == targetType)
- Non-sealed types: Uses assignability check to include derived types (targetType.IsAssignableFrom(memberType))
- Open generic types: Matches closed generics and checks inheritance hierarchy for all derived types
Comprehensive XML documentation for all public APIs
Updated documentation in objectgraphs.md and releases.md

Testing

Added 21 unit tests covering all scenarios including inheritance cases
All 628 existing equivalency tests pass (no regressions)
Full test suite: 5,875+ tests passing
Manual verification confirms all use cases work correctly

Breaking Changes

None. This is a purely additive change that maintains full backward compatibility.

Fixes #2390

Original prompt

This section details on the original issue you should resolve

<issue_title>[API Proposal]: Allow BeEquivalentTo to exclude all members of a certain type</issue_title>
<issue_description>### Background and motivation

A shortcut to options.Excluding(mi => mi.Type == typeof(TimeSpan));

API Proposal
public abstract class SelfReferenceEquivalencyAssertionOptions<TSelf> : IEquivalencyOptions
    where TSelf : SelfReferenceEquivalencyAssertionOptions<TSelf>
{
    public TSelf Excluding<TMember>()
    {
    }
}
Also supports excluding all members whose type is assignable to IMyInterface

options.Excluding<IMyInterface>();

And excludeing all members whose type is a closed generic of Nullable<T>, i.e. it excludes int?, double?, etc.

options.Excluding(typeof(Nullable<>))

API Usage

Instead of options.Excluding(mi => mi.Type == typeof(TimeSpan));, you can do options.Excluding<TimeSpan>()

Alternative Designs

Maybe name it ExcludingMembersOfType<T>

Risks

No response

Are you willing to help with a proof-of-concept (as PR in that or a separate repo) first and as pull-request later on?

No</issue_description>

Comments on the Issue (you are @copilot in this section)
@jnyrup Should this also be able to handle polymorphism and open generic types?
Examples:

Excludes all members whose type is assignable to MyInterface
options.Excluding<MyInterface>()
Excludes all members whose type is a closed generic of Nullable<T>, i.e. it excludes int?, double?, etc.
options.Excluding(typeof(Nullable<>))
```</body></comment_new>
<comment_new><author>@dennisdoomen</author><body>
I like that. Let's do that.</body></comment_new>
</comments>

Fixes #3114

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dennisdoomen · 2025-10-18T08:02:01Z

Tests/FluentAssertions.Equivalency.Specs/SelectionRulesSpecs.ExcludingByType.cs

+    public class ExcludingByType
+    {
+        [Fact]
+        public void When_excluding_members_by_type_it_should_exclude_exact_type_matches()


@copilot don't use terms like "when" and "should", but instead use a current or future tense form for all test name.

Renamed all test methods to use present/future tense without "when" and "should" (commit edeadd1).

Src/FluentAssertions/Equivalency/Selection/ExcludeMemberByTypeSelectionRule.cs

dennisdoomen

Also update the objectgraphs.md and releases.md

Src/FluentAssertions/Equivalency/Selection/ExcludeMemberByTypeSelectionRule.cs

github-actions · 2025-10-18T09:13:55Z

Test Results

37 files ± 0 37 suites ±0 2m 53s ⏱️ +5s
6 288 tests + 20 6 288 ✅ + 20 0 💤 ±0 0 ❌ ±0
39 074 runs +120 39 074 ✅ +120 0 💤 ±0 0 ❌ ±0

Results for commit 56a159e. ± Comparison against base commit d73f064.

This pull request removes 10 and adds 28 tests. Note that renamed tests count towards both.

FluentAssertions.Specs.Streams.StreamAssertionSpecs+HaveLength ‑ When_a_throwing_stream_should_have_a_length_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+HaveLength ‑ When_a_throwing_stream_should_have_a_length_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+HavePosition ‑ When_a_throwing_stream_should_have_a_position_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+HavePosition ‑ When_a_throwing_stream_should_have_a_position_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+NotHaveLength ‑ When_a_throwing_stream_should_not_have_a_length_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+NotHaveLength ‑ When_a_throwing_stream_should_not_have_a_length_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+NotHavePosition ‑ When_a_throwing_stream_should_not_have_a_position_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
FluentAssertions.Specs.Streams.StreamAssertionSpecs+NotHavePosition ‑ When_a_throwing_stream_should_not_have_a_position_it_should_fail(exception: System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'GetLengthExceptionMessage'.)
Object name: 'GetPositionExceptionMessage'.)

FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_all_closed_generic_types
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_all_types_deriving_from_an_abstract_type
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_all_types_implementing_a_generic_interface
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_exact_type_using_a_type_instance
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_exact_type_using_a_type_parameter
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_multiple_types
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Can_exclude_value_types
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Excluding_applies_to_all_levels_in_a_nested_structure
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Excluding_applies_to_collections_as_well
FluentAssertions.Equivalency.Specs.SelectionRulesSpecs+ExcludingByType ‑ Excluding_by_type_with_nested_generics_works
…

♻️ This comment has been updated with latest results.

Copilot · 2025-10-18T09:14:14Z

Also update the objectgraphs.md and releases.md

Updated both objectgraphs.md and releases.md with documentation for the new Excluding<T>() and Excluding(Type) methods.

github-actions · 2025-10-18T09:18:47Z

Qodana for .NET

5 new problems were found

Inspection name	Severity	Problems
`Auto-property accessor is never used (private accessibility)`	🔶 Warning	3
`Redundant using directive`	🔶 Warning	1
`Unused type parameter`	🔶 Warning	1

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…by type Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

…hould" Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

github-actions · 2025-12-14T12:22:50Z

Qodana for .NET

It seems all right 👌

No new problems were found according to the checks applied

💡 Qodana analysis was run in the pull request mode: only the changed files were checked
☁️ View the detailed Qodana report

Contact Qodana team

Contact us at qodana-support@jetbrains.com

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Or share your feedback: https://jb.gg/qodana-discussions

coveralls · 2025-12-14T12:40:34Z

Pull Request Test Coverage Report for Build 20550527439

Details

23 of 23 (100.0%) changed or added relevant lines in 2 files are covered.
5 unchanged lines in 2 files lost coverage.
Overall coverage decreased (-0.02%) to 97.164%

Files with Coverage Reduction	New Missed Lines	%
Src/FluentAssertions/Equivalency/Steps/EnumerableEquivalencyValidator.cs	2	96.15%
Src/FluentAssertions/Equivalency/Node.cs	3	87.8%

Totals
Change from base Build 20440195444:	-0.02%
Covered Lines:	12849
Relevant Lines:	13068

💛 - Coveralls

Tests/FluentAssertions.Equivalency.Specs/SelectionRulesSpecs.ExcludingByType.cs

Src/FluentAssertions/Equivalency/Selection/ExcludeMemberByTypeSelectionRule.cs

…lentTo

github-actions · 2025-12-28T07:30:30Z

Qodana for .NET

It seems all right 👌

No new problems were found according to the checks applied

💡 Qodana analysis was run in the pull request mode: only the changed files were checked
☁️ View the detailed Qodana report

Contact Qodana team

Contact us at qodana-support@jetbrains.com

Or via our issue tracker: https://jb.gg/qodana-issue
Or share your feedback: https://jb.gg/qodana-discussions

Copilot AI assigned Copilot and dennisdoomen Oct 18, 2025

Copilot started work on behalf of dennisdoomen October 18, 2025 07:37 View session

Copilot AI changed the title ~~[WIP] Add API options for excluding member types~~ Add Excluding<T>() and Excluding(Type) methods to exclude members by type in equivalency assertions Oct 18, 2025

Copilot AI requested a review from dennisdoomen October 18, 2025 07:50

Copilot finished work on behalf of dennisdoomen October 18, 2025 07:50

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jnyrup reviewed Oct 18, 2025

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Src/FluentAssertions/Equivalency/Selection/ExcludeMemberByTypeSelectionRule.cs Show resolved Hide resolved

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Src/FluentAssertions/Equivalency/Selection/ExcludeMemberByTypeSelectionRule.cs Show resolved Hide resolved

Copilot started work on behalf of dennisdoomen October 18, 2025 09:06 View session

Copilot AI changed the title ~~Add Excluding<T>() and Excluding(Type) methods to exclude members by type in equivalency assertions~~ Add Excluding by type with inheritance support Oct 18, 2025

Copilot finished work on behalf of dennisdoomen October 18, 2025 09:15

Copilot AI requested a review from dennisdoomen October 18, 2025 09:15

Copilot AI and others added 4 commits December 14, 2025 13:08

Initial plan

c3dd3f1

Add Excluding<T>() and Excluding(Type) methods for excluding members …

98403b8

…by type Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

Add additional tests for edge cases in Excluding by type feature

15397ed

Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

Rename test methods to use present/future tense without "when" and "s…

d69b765

…hould" Co-authored-by: dennisdoomen <572734+dennisdoomen@users.noreply.github.com>

dennisdoomen force-pushed the copilot/add-excluding-options-to-api branch from 6fb54bc to 1b5e9a0 Compare December 14, 2025 12:08

dennisdoomen force-pushed the copilot/add-excluding-options-to-api branch from 1b5e9a0 to 4033707 Compare December 14, 2025 12:30

dennisdoomen force-pushed the copilot/add-excluding-options-to-api branch 3 times, most recently from 8231fea to c6fcbe4 Compare December 14, 2025 19:54

dennisdoomen marked this pull request as ready for review December 14, 2025 19:55

dennisdoomen requested a review from jnyrup December 14, 2025 19:55

dennisdoomen approved these changes Dec 14, 2025

View reviewed changes

jnyrup requested changes Dec 15, 2025

View reviewed changes

Add support for excluding members by ((open)generic) type in BeEquiva…

56a159e

…lentTo

dennisdoomen force-pushed the copilot/add-excluding-options-to-api branch from c6fcbe4 to 56a159e Compare December 28, 2025 07:18

dennisdoomen requested a review from jnyrup December 28, 2025 07:20

jnyrup approved these changes Dec 28, 2025

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dennisdoomen merged commit dc2445b into main Dec 28, 2025
14 checks passed

dennisdoomen deleted the copilot/add-excluding-options-to-api branch December 28, 2025 08:11

dennisdoomen added the enhancement label Dec 28, 2025

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Add Excluding by type with inheritance support #3115

Add Excluding by type with inheritance support #3115

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Summary

Motivation

Changes

1. Generic Method: Excluding<TMember>()

2. Type Parameter Method: Excluding(Type type)

Features

Type Matching with Inheritance Support

Sealed Type Matching

Interface and Abstract Type Support

Open Generic Type Matching with Full Inheritance Support

Multiple Exclusions

Works at All Nesting Levels

Implementation Details

Testing

Breaking Changes

API Proposal

API Usage

Alternative Designs

Risks

Are you willing to help with a proof-of-concept (as PR in that or a separate repo) first and as pull-request later on?

Comments on the Issue (you are @copilot in this section)

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Copilot AI commented Oct 18, 2025 •

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1. Generic Method: `Excluding<TMember>()`

2. Type Parameter Method: `Excluding(Type type)`

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