Constructor Binding with ConfigurationKeyName attribute fails to bind correctly

[bbartels]

Description

When binding root-level configuration properties using Microsoft.Extensions.Configuration.Binder, binding to a record defined with a positional parameter decorated with [ConfigurationKeyName] fails to bind the expected value (throws Exception), while binding to a class with an attributed property works as expected. The following minimal reproducible example demonstrates the issue.

Reproduction Steps

using System;
using System.Collections.Generic;
using Microsoft.Extensions.Configuration;
#nullable disable

var inMemorySettings = new Dictionary<string, string>
{
    { "example-secret-key", "my-secret-value" }
};

IConfiguration configuration = new ConfigurationBuilder()
    .AddInMemoryCollection(inMemorySettings)
    .Build();

var secretsClass = configuration.Get<ExampleSecretsClass>();
Console.WriteLine("ExampleSecretsClass.SecretKey: " + (secretsClass?.SecretKey ?? "null"));

var secretsRecord = configuration.Get<ExampleSecretsRecord>();
Console.WriteLine("ExampleSecretsRecord.SecretKey: " + (secretsRecord?.SecretKey ?? "null"));

public class ExampleSecretsClass
{
    [ConfigurationKeyName("example-secret-key")]
    public string SecretKey { get; init; } = string.Empty;
}

public record ExampleSecretsRecord([property: ConfigurationKeyName("example-secret-key")] string SecretKey);

Expected behavior

When using constructor binding with ConfigurationKeyName, the binding fails and an Exception is thrown

Actual behavior

It should bind even when constructor binding is used

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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[ericstj]

Seems like this is a feature request to honor attributes on properties when mapping those to constructor parameters. Today it looks like the binder will only use the exact parameter names when mapping to configuration properties

runtime/src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

Lines 591 to 598 in 8a9d492

	foreach (ParameterInfo parameter in parameters)
	{
	string name = parameter.Name!;
	if (!propertyNames.Contains(name))
	{
	missingParameters.Add(name);
	}
	}

I can also imagine that we allow for applying the attribute to the constructor parameter.

[ericstj]

Looks similar to #79957 which may be a duplicate / superset of this.

[ericstj]

@bbartels as a workaround you can try

public record ExampleSecretsRecord([property: ConfigurationKeyName("example-secret-key")] string SecretKey)
{
    public ExampleSecretsRecord() : this(string.Empty) { }
}

That would allow the ConfigurationBinder to construct the object and bind to the properties instead of constructor parameters.

Note that neither type here will work well with the source-generator because it doesn't support init properties. #107856