Keep empty collections ignored alongside instance predicates (#1860)

TryGetScrubOrIgnoreByInstance returned as soon as it found predicates registered
for the value's type and none of them matched, skipping the empty collection
check below it. So an empty List<string> started rendering as [] merely because
some unrelated IgnoreInstance or ScrubInstance predicate had been registered for
that type.

No predicate matching is not a decision to keep the value, so the empty
collection check now runs either way.

The test lives in its own file rather than being appended to SerializationTests,
so this does not collide with the other pending fixes that append there.

Author: SimonCropp

src/Verify.Tests/Serialization/IgnoreInstanceTests.NonMatchingPredicateKeepsEmptyCollectionsIgnored.verified.txt

@@ -0,0 +1,5 @@
+{
+  NotEmpty: [
+    TheValue
+  ]
+}

src/Verify.Tests/Serialization/IgnoreInstanceTests.cs

@@ -0,0 +1,17 @@
+public class IgnoreInstanceTests
+{
+    [Fact]
+    public Task NonMatchingPredicateKeepsEmptyCollectionsIgnored() =>
+        Verify(
+            new
+            {
+                Empty = new List<string>(),
+                NotEmpty = new List<string>
+                {
+                    "TheValue"
+                }
+            })
+            // a predicate that never matches is not a decision to keep the value,
+            // so Empty is still ignored as an empty collection
+            .IgnoreInstance<List<string>>(_ => false);
+}

src/Verify/Serialization/SerializationSettings_ShouldIgnore.cs

@@ -23,6 +23,8 @@ internal bool TryGetScrubOrIgnore(Type declaringType, Type memberType, string na
     internal bool TryGetScrubOrIgnoreByInstance(object value, [NotNullWhen(true)] out ScrubOrIgnore? scrubOrIgnore)
     {
         var memberType = value.GetType();
+        // no predicate matching is not a decision to keep the value, so
+        // the empty collection check still applies
         if (GetShouldIgnoreInstance(memberType, out var funcs))
         {
             foreach (var func in funcs)
@@ -34,9 +36,6 @@ internal bool TryGetScrubOrIgnoreByInstance(object value, [NotNullWhen(true)] ou
                     return true;
                 }
             }
-
-            scrubOrIgnore = null;
-            return false;
         }
 
         if (ignoreEmptyCollections &&

src/todo.md

@@ -44,7 +44,7 @@ All six resolved 2026-08-16 (five fixed here; the inline item resolved as by-des
 - [ ] **`MemberConverter` has no exact-type precedence.**
   `Verify/Serialization/VerifierSettings_MemberConverter.cs:13-25` — first registered entry with `IsAssignableFrom` wins, so a base-interface converter registered earlier permanently shadows a more specific one. Contrast `TryGetScrubOrIgnoreByMemberOfType`, which checks the exact declaring type first.
 
-- [ ] **Registering an `IgnoreInstance` predicate disables empty-collection ignoring for that type.**
+- [x] **Registering an `IgnoreInstance` predicate disables empty-collection ignoring for that type.**
   `Verify/Serialization/SerializationSettings_ShouldIgnore.cs:26-40` — when predicates exist but none match, the early `return false` skips the `ignoreEmptyCollections` check at 42-47. An empty `List<string>` starts appearing as `[]` merely because an unrelated predicate was registered.
 
 - [x] **Combinations name cache collapses distinct keys.**