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Compile lambda for null access expressions #3157

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Merged
merged 2 commits into from
Sep 14, 2022
Merged

Compile lambda for null access expressions #3157

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Compile lambda for null access expressions
bahusoid Sep 12, 2022
7376d1a
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bahusoid Sep 12, 2022
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30 changes: 30 additions & 0 deletions src/NHibernate.Test/Criteria/Lambda/ExpressionProcessorFindValueFixture.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,36 @@ public void StaticPropertyInstanceMethodCall()

Assert.AreEqual(expected, actual);
}

[Test]
public void NullableNullHasValue()
{
int? v = null;
var actual = GetValue(() => v.HasValue);
var expected = v.HasValue;

Assert.AreEqual(expected, actual);
}

[Test]
public void NullableNullGetValueOrDefault()
{
int? v = null;
var actual = GetValue(() => v.GetValueOrDefault());
var expected = v.GetValueOrDefault();

Assert.AreEqual(expected, actual);
}

[Test]
public void NullableNullValue()
{
int? v = null;
Expression<Func<int>> expression = () => v.Value;

Assert.Throws<InvalidCastException>(() => GetValue(expression));
Assert.Throws<InvalidCastException>(() => expression.Compile().Invoke());
}
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@fredericDelaporte fredericDelaporte Sep 12, 2022 •
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What about e => v.HasValue || e.SomeProperty = v.Value? I wonder if it is supported or if it would throw.

(There is not much value in supporting this, excepted "feature parity" with linq-to-object: the .Value is not needed in any way in such a query and can just be dropped. But still, it is better to know what how it behaves with NHibernate.)

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It throws on v.Value evaluation:

    NHibernate.HibernateException : Evaluation failure on null.Value
  ----> System.InvalidOperationException : Nullable object must have a value.

Maybe we shouldn't try to evaluate it in this context. But it's a different story not related to this PR.

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For sure, it would be beneficial if nullable.Value works (with the SQL parameter becoming false, true, or NULL). The value of supporting this would be that users don't have to remember to adapt their expression specially.

No idea what the effort would be to support it though.

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it would be beneficial if nullable.Value works

Just to clarify things. This PR fixes regression caused by optimizations made in #2948, #2957. nullableNullParam.HasValue or nullableNullParam.GetValueOrDefault() works in 5.3 but throws on master (5.4-dev).

nullable.Value fails the same in 5.3. So it's more like another feature request.


[Test]
public void StaticPropertyInstanceMultipleMethodCall()
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11 changes: 9 additions & 2 deletions src/NHibernate/Impl/ExpressionProcessor.cs
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Expand Up @@ -261,18 +261,25 @@ public static object FindValue(Expression expression)
return constantExpression.Value;
case ExpressionType.MemberAccess:
var memberExpression = (MemberExpression) expression;
var instance = findValue(memberExpression.Expression);
if (instance == null && memberExpression.Expression != null)
break;

switch (memberExpression.Member.MemberType)
{
case MemberTypes.Field:
return ((FieldInfo) memberExpression.Member).GetValue(findValue(memberExpression.Expression));
return ((FieldInfo) memberExpression.Member).GetValue(instance);
case MemberTypes.Property:
return ((PropertyInfo) memberExpression.Member).GetValue(findValue(memberExpression.Expression));
return ((PropertyInfo) memberExpression.Member).GetValue(instance);
}
break;
case ExpressionType.Call:
var methodCallExpression = (MethodCallExpression) expression;
var args = methodCallExpression.Arguments.ToArray(arg => FindValue(arg));
var callingObject = findValue(methodCallExpression.Object);
if (callingObject == null && methodCallExpression.Object != null)
break;

return methodCallExpression.Method.Invoke(callingObject, args);
case ExpressionType.Convert:
var unaryExpression = (UnaryExpression) expression;
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