Annotate ChangeTracking for nullability by smitpatel · Pull Request #24261 · dotnet/efcore

smitpatel · 2021-02-24T19:55:14Z

Part of #19007

roji · 2021-02-25T07:51:15Z

        /// <param name="value"> The property value if any. </param>
        /// <returns> True if the property exists, otherwise false. </returns>
-        public virtual bool TryGetValue<TValue>([NotNull] string propertyName, out TValue value)
+        public virtual bool TryGetValue<TValue>([NotNull] string propertyName, out TValue? value)


Probably [NotNullWhen(true)]

But the value can be null even when true

It's the same logic as with GetValue above (or with ReadShadowValue), i.e. whether the user calls TryGetValue<string> or TryGetValue<string?>`. We should make a global decision on that and apply everywhere.

I think this is still left, since we made the decision to have GetValue return TValue and not TValue?.

Part of #19007

Updated and re-requested review.

ghost · 2021-02-25T23:45:53Z

Hello @smitpatel!

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ghost · 2021-02-25T23:54:31Z

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roji · 2021-02-26T08:54:49Z

+                if (value == null)
                {
-                    return null;
+                    return default!;


Shouldn't this method return object[]? (and possibly banged at relevant call sites)? Though as long as it's correct, it's just a private function so no big deal.

small nit: I (now) usually use default! only in generic contexts. In reference type contexts like this one, I tend to use null! for more clarity.

Long chain.
So basically this implements PrincipalKeyValueFactory<object[]> hence type becomes non-nullable. The reason for T = object[] because it is used as dependents map which uses dict underneath which cannot use nullable type as key. So while it is default! it shouldn't hit the code path here.

roji · 2021-02-26T09:02:32Z

                if (index != -1)
                {
-                    ((HashSet<object>)_values[index])?.Remove(removedEntity);
+                    ((HashSet<object>)_values[index]!)?.Remove(removedEntity);


If you want the runtime check, remove the bang; if we know it should never be null, remove the question mark.

roji · 2021-02-26T09:10:23Z


            public T GetValue<T>(int index)
-                => IsEmpty ? default : _values.GetValue<T>(index);
+                => IsEmpty ? default! : _values.GetValue<T>(index);


This could be a case where it's more correct to return T?, since there's an additional Empty state. Is the user expected to know before calling this whether it's empty or not? If not, we probably want to force them to deal with the Empty state.

The way whole T of GetValue flows, this shouldn't be invoked with non-null type if it can be empty. It is same as we returning T from other places, if you ask for wrong nullability it will throw exception. default! throws exception for us. @ajcvickers - Thoughts?

roji

Looks almost perfect, see comments below.

roji · 2021-02-26T09:43:42Z

May bad, forgot to remove auto-merge, sorry.

Following #24261