Support for required properties #1355
Description
Problem Statement
Traditionally, Autofac creates objects by calling one of their constructors. The constructor accepts dependencies and then assigns/initializes values.
Starting in C#11, dependencies can also be expressed using the required keyword. When a property is required, if the constructor that was called does not have the [SetsRequiredMembers] attribute, the property must have a value set immediately following construction.
Currently AutoFac does not support this core enhancement to object construction.
Desired Solution
When Autofac constructs an object, the constructor should be examined for [SetsRequiredMembers]. If it is not found, all writable properties containing the RequiredMemberAttribute attribute should be injected.
public class Foo1 {
//This should be injected
public required Dependency? Dep { protected get; init; }
}
public class Foo2 {
//This should not
public required Dependency? Dep { protected get; init; }
[SetsRequiredMembers]
public Foo2() {
this.Dep = null;
}
}Additional Context
Because C#11 introduces this core-level enhancement to object construction, the above rules should always be enabled.
The following code will be helpful in implementing this enhancement:
public class PS : IPropertySelector {
public static IPropertySelector Instance { get; }
private static string RequiredAttributeName { get; }
private static string SetsRequiredMembersAttributeName { get; }
static PS() {
Instance = new PS();
//The type names are stored as strings so that this can also be used with legacy .NET platforms
RequiredAttributeName = "System.Runtime.CompilerServices.RequiredMemberAttribute";
SetsRequiredMembersAttributeName = "System.Diagnostics.CodeAnalysis.SetsRequiredMembersAttribute";
}
public bool NeedsPropertyInjection(ConstructorInfo constructorInfo) {
var SetsRequiredMembers = constructorInfo.GetCustomAttributesData().Any(x => string.Equals(x.AttributeType.FullName, SetsRequiredMembersAttributeName, StringComparison.InvariantCultureIgnoreCase));
var ret = !SetsRequiredMembers;
return ret;
}
public bool InjectProperty(PropertyInfo propertyInfo, object instance) {
var ret = propertyInfo.CanWrite
&& propertyInfo.GetCustomAttributesData().Any(x => string.Equals(x.AttributeType.FullName, RequiredAttributeName, StringComparison.InvariantCultureIgnoreCase))
;
return ret;
}
}