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Avoid closures in JsonPropertyInfoOfT/JsonTypeInfoOfT #117498

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Avoid closures in JsonPropertyInfoOfT/JsonTypeInfoOfT #117498

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12 changes: 6 additions & 6 deletions ...aries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfoOfT.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,12 +46,12 @@ private protected override void SetGetter(Delegate? getter)
else if (getter is Func<object, T> typedGetter)
{
_typedGet = typedGetter;
_untypedGet = getter is Func<object, object?> untypedGet ? untypedGet : obj => typedGetter(obj);
_untypedGet = getter is Func<object, object?> untypedGet ? untypedGet : obj => _typedGet(obj);
}
else
{
Func<object, object?> untypedGet = (Func<object, object?>)getter;
_typedGet = (obj => (T)untypedGet(obj)!);
_typedGet = (obj => (T)_untypedGet!(obj)!);
_untypedGet = untypedGet;
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@stephentoub stephentoub Jul 10, 2025 •
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Nit: it doesn't actually matter, because the delegate won't be invoked yet, but could we switch these two lines so that _untypedGet is set before it's referenced? I find it a bit easier to reason about. (You might also be able to remove the !, I'm not sure)

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Hypothetically, if I called the getter to store a copy of the existing delegate, but then set a new delegate via the setter, my copy would start pointing to the new behaviour. I think that makes a subtle difference that could regress code that is heavy on contract customization.

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Hypothetically, if I called the getter to store a copy of the existing delegate, but then set a new delegate via the setter, my copy would start pointing to the new behaviour. I think that makes a subtle difference that could regress code that is heavy on contract customization.

This is in reference to the PR, not to my nit, yes?

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Yep

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Does this mean I should close this?

I don't mind either way. This is a drop in the bucket. I'm looking at a relatively big app (40 MB) where 15% of the app is System.Text.Json because of how many generics S.T.Json will create for every type used with Json. This looked like something we could do something about, the rest I don't know how to fix.

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Does this mean I should close this?

Yeah I think so. It doesn't change things much either way so I would err towards preserving the current behaviour.

}
}
Expand All @@ -69,12 +69,12 @@ private protected override void SetSetter(Delegate? setter)
else if (setter is Action<object, T> typedSetter)
{
_typedSet = typedSetter;
_untypedSet = setter is Action<object, object?> untypedSet ? untypedSet : (obj, value) => typedSetter(obj, (T)value!);
_untypedSet = setter is Action<object, object?> untypedSet ? untypedSet : (obj, value) => _typedSet(obj, (T)value!);
}
else
{
Action<object, object?> untypedSet = (Action<object, object?>)setter;
_typedSet = ((obj, value) => untypedSet(obj, value));
_typedSet = ((obj, value) => _untypedSet!(obj, value));
_untypedSet = untypedSet;
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Ditto

}
}
Expand All @@ -100,12 +100,12 @@ private protected override void SetShouldSerialize(Delegate? predicate)
else if (predicate is Func<object, T?, bool> typedPredicate)
{
_shouldSerializeTyped = typedPredicate;
_shouldSerialize = typedPredicate is Func<object, object?, bool> untypedPredicate ? untypedPredicate : (obj, value) => typedPredicate(obj, (T?)value);
_shouldSerialize = typedPredicate is Func<object, object?, bool> untypedPredicate ? untypedPredicate : (obj, value) => _shouldSerializeTyped(obj, (T?)value);
}
else
{
Func<object, object?, bool> untypedPredicate = (Func<object, object?, bool>)predicate;
_shouldSerializeTyped = (obj, value) => untypedPredicate(obj, value);
_shouldSerializeTyped = (obj, value) => _shouldSerialize!(obj, value);
_shouldSerialize = untypedPredicate;
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Ditto

}
}
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4 changes: 2 additions & 2 deletions ...libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfoOfT.cs
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Expand Up @@ -86,13 +86,13 @@ private protected override void SetCreateObject(Delegate? createObject)
else if (createObject is Func<T> typedDelegate)
{
typedCreateObject = typedDelegate;
untypedCreateObject = createObject is Func<object> untypedDelegate ? untypedDelegate : () => typedDelegate()!;
untypedCreateObject = createObject is Func<object> untypedDelegate ? untypedDelegate : () => _typedCreateObject!()!;
}
else
{
Debug.Assert(createObject is Func<object>);
untypedCreateObject = (Func<object>)createObject;
typedCreateObject = () => (T)untypedCreateObject();
typedCreateObject = () => (T)_createObject!();
}

_createObject = untypedCreateObject;
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