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Update ResilienceProperties to correctly handle null values #2300

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merged 3 commits into from
Sep 26, 2024
Merged

Update ResilienceProperties to correctly handle null values #2300

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7249a68
Fixes #2299
iliar-turdushev Sep 20, 2024
864e2eb
Replaces "val == null" with "val is null"
iliar-turdushev Sep 20, 2024
1392bec
Added a comment describing the need to use "!" operator
iliar-turdushev Sep 26, 2024
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20 changes: 17 additions & 3 deletions src/Polly.Core/ResilienceProperties.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,24 @@ public sealed class ResilienceProperties
/// <returns>True, if a property was retrieved.</returns>
public bool TryGetValue<TValue>(ResiliencePropertyKey<TValue> key, [MaybeNullWhen(false)] out TValue value)
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{
if (Options.TryGetValue(key.Key, out object? val) && val is TValue typedValue)
if (Options.TryGetValue(key.Key, out object? val))
{
value = typedValue;
return true;
if (val is TValue typedValue)
{
value = typedValue;
return true;
}
else if (val is null)
{
// We have to use null-forgiving operator "!" here to suppress a null-state analysis warning.
// The reason is the following. The output type "TValue" doesn't have any type constraints as
// "notnull", "class" or "struct", therefore the analyzer considers "TValue" as non-nullable
// and warns us that we're assigning "null" to it. But that's not correct, because "TValue"
// could be a nullable type, e.g. "string?", and assigning "null" to it is correct. Therefore
// it is reasonable to use "!" here to suppress the warning.
value = default!;
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return true;
}
}

value = default;
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23 changes: 23 additions & 0 deletions test/Polly.Core.Tests/ResiliencePropertiesTests.cs
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Expand Up @@ -14,6 +14,18 @@ public void TryGetValue_Ok()
val.Should().Be(12345);
}

[Fact]
public void TryGetValue_ValueIsNull_Ok()
{
var key = new ResiliencePropertyKey<string?>("dummy");
var props = new ResilienceProperties();

props.Set(key, null);

props.TryGetValue(key, out var val).Should().Be(true);
val.Should().Be(null);
}

[Fact]
public void TryGetValue_NotFound_Ok()
{
Expand All @@ -34,6 +46,17 @@ public void GetValue_Ok()
props.GetValue(key, default).Should().Be(12345);
}

[Fact]
public void GetValue_ValueIsNull_Ok()
{
var key = new ResiliencePropertyKey<string?>("dummy");
var props = new ResilienceProperties();

props.Set(key, null);

props.GetValue(key, "default").Should().Be(null);
}

[Fact]
public void GetValue_NotFound_EnsureDefault()
{
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