ResourceFieldAttribute.cs

using System.Reflection;
using JetBrains.Annotations;
using JsonApiDotNetCore.Configuration;

// ReSharper disable NonReadonlyMemberInGetHashCode

namespace JsonApiDotNetCore.Resources.Annotations;

/// <summary>
/// Used to expose a property on a resource class as a JSON:API field (attribute or relationship). See
/// https://jsonapi.org/format/#document-resource-object-fields.
/// </summary>
[PublicAPI]
public abstract class ResourceFieldAttribute : Attribute
{
    // These are definitely assigned after building the resource graph, which is why their public equivalents are declared as non-nullable.
    private string? _publicName;
    private PropertyInfo? _property;
    private ResourceType? _type;

    /// <summary>
    /// The publicly exposed name of this JSON:API field. When not explicitly set, the configured naming convention is applied on the property name.
    /// </summary>
    public string PublicName
    {
        get => _publicName!;
        set
        {
            if (string.IsNullOrWhiteSpace(value))
            {
                throw new ArgumentException("Exposed name cannot be null, empty or contain only whitespace.", nameof(value));
            }

            _publicName = value;
        }
    }

    /// <summary>
    /// The resource property that this attribute is declared on.
    /// </summary>
    public PropertyInfo Property
    {
        get => _property!;
        internal set
        {
            ArgumentNullException.ThrowIfNull(value);
            _property = value;
        }
    }

    /// <summary>
    /// The containing resource type in which this field is declared.
    /// </summary>
    public ResourceType Type
    {
        get => _type!;
        internal set
        {
            ArgumentNullException.ThrowIfNull(value);
            _type = value;
        }
    }

    /// <summary>
    /// Gets the value of this field on the specified resource instance. Throws if the property is write-only or if the field does not belong to the
    /// specified resource instance.
    /// </summary>
    public object? GetValue(object resource)
    {
        ArgumentNullException.ThrowIfNull(resource);
        AssertIsIdentifiable(resource);

        if (Property.GetMethod == null)
        {
            throw new InvalidOperationException($"Property '{Property.DeclaringType?.Name}.{Property.Name}' is write-only.");
        }

        try
        {
            return Property.GetValue(resource);
        }
        catch (TargetException exception)
        {
            throw new InvalidOperationException(
                $"Unable to get property value of '{Property.DeclaringType!.Name}.{Property.Name}' on instance of type '{resource.GetType().Name}'.",
                exception.InnerException ?? exception);
        }
    }

    /// <summary>
    /// Sets the value of this field on the specified resource instance. Throws if the property is read-only or if the field does not belong to the specified
    /// resource instance.
    /// </summary>
    public virtual void SetValue(object resource, object? newValue)
    {
        ArgumentNullException.ThrowIfNull(resource);
        AssertIsIdentifiable(resource);

        if (Property.SetMethod == null)
        {
            throw new InvalidOperationException($"Property '{Property.DeclaringType?.Name}.{Property.Name}' is read-only.");
        }

        try
        {
            Property.SetValue(resource, newValue);
        }
        catch (TargetException exception)
        {
            throw new InvalidOperationException(
                $"Unable to set property value of '{Property.DeclaringType!.Name}.{Property.Name}' on instance of type '{resource.GetType().Name}'.",
                exception.InnerException ?? exception);
        }
    }

    protected void AssertIsIdentifiable(object? resource)
    {
        if (resource is not null and not IIdentifiable)
        {
#pragma warning disable CA1062 // Validate arguments of public methods
            throw new InvalidOperationException($"Resource of type '{resource.GetType()}' does not implement {nameof(IIdentifiable)}.");
#pragma warning restore CA1062 // Validate arguments of public methods
        }
    }

    /// <inheritdoc />
    public override string? ToString()
    {
        return _publicName ?? (_property != null ? _property.Name : base.ToString());
    }

    public string ToFullString()
    {
        return $"{_type?.PublicName}:{ToString()}";
    }

    /// <inheritdoc />
    public override bool Equals(object? obj)
    {
        if (ReferenceEquals(this, obj))
        {
            return true;
        }

        if (obj is null || GetType() != obj.GetType())
        {
            return false;
        }

        var other = (ResourceFieldAttribute)obj;

        return _publicName == other._publicName && _property == other._property;
    }

    /// <inheritdoc />
    public override int GetHashCode()
    {
        return HashCode.Combine(_publicName, _property);
    }
}