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[release/6.0] [mono] Use string.Empty for empty string custom arg values #58113

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Merged
marek-safar merged 2 commits into from
Aug 27, 2021
Merged

[release/6.0] [mono] Use string.Empty for empty string custom arg values #58113

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5c47007
[mono] Use string.Empty for empty string custom arg values
uweigand Aug 24, 2021
ce2242f
Add test that GetCustomAttribute returns string.Empty
lambdageek Aug 26, 2021
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53 changes: 53 additions & 0 deletions src/libraries/System.Reflection/tests/CustomAttributeTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -76,5 +76,58 @@ public void AttributeWithDifferentPropertyTypes()
Assert.Equal(1, attr.ObjectArray.Length);
Assert.Null(attr.StringArray);
}

public class StringValuedAttribute : Attribute
{
public StringValuedAttribute (string s)
{
NamedField = s;
}
public StringValuedAttribute () {}
public string NamedProperty
{
get => NamedField;
set { NamedField = value; }
}
public string NamedField;
}

internal class ClassWithAttrs
{
[StringValuedAttribute("")]
public void M1() {}

[StringValuedAttribute(NamedProperty = "")]
public void M2() {}

[StringValuedAttribute(NamedField = "")]
public void M3() {}
}

[Fact]
public void StringAttributeValueRefEqualsStringEmpty () {
StringValuedAttribute attr;
attr = typeof (ClassWithAttrs).GetMethod("M1")
.GetCustomAttributes(typeof(StringValuedAttribute), true)
.Cast<StringValuedAttribute>()
.Single();

Assert.Same(string.Empty, attr.NamedField);

attr = typeof (ClassWithAttrs).GetMethod("M2")
.GetCustomAttributes(typeof(StringValuedAttribute), true)
.Cast<StringValuedAttribute>()
.Single();

Assert.Same(string.Empty, attr.NamedField);


attr = typeof (ClassWithAttrs).GetMethod("M3")
.GetCustomAttributes(typeof(StringValuedAttribute), true)
.Cast<StringValuedAttribute>()
.Single();

Assert.Same(string.Empty, attr.NamedField);
}
}
}
6 changes: 5 additions & 1 deletion src/mono/mono/metadata/custom-attrs.c
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Expand Up @@ -397,7 +397,11 @@ MONO_RESTORE_WARNING
// to decode some attributes in assemblies that Windows .NET Framework
// and CoreCLR both manage to decode.
// See https://simonsapin.github.io/wtf-8/ for a description of wtf-8.
*out_obj = (MonoObject*)mono_string_new_wtf8_len_checked (p, slen, error);
// Always use string.Empty for empty strings
if (slen == 0)
*out_obj = (MonoObject*)mono_string_empty_internal (mono_domain_get ());
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@marek-safar marek-safar Aug 27, 2021

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nit: wouldn't mono_string_empty_wrapper be better?

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@akoeplinger akoeplinger Aug 27, 2021

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that one is marked MONO_RT_EXTERNAL_ONLY so cannot be used in runtime code.

else
*out_obj = (MonoObject*)mono_string_new_wtf8_len_checked (p, slen, error);
return NULL;
}
case MONO_TYPE_CLASS: {
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