AutoClassDataSourceAttribute.cs

using System.Diagnostics.CodeAnalysis;
using AutoFixture.TUnit.Internal;

namespace AutoFixture.TUnit;

/// <summary>
/// Provides a data source for a data theory, with the data coming from a class
/// which must implement IEnumerable&lt;object?[]&gt;,
/// combined with auto-generated data specimens generated by AutoFixture.
/// </summary>
[SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes",
    Justification = "This attribute is the root of a potential attribute hierarchy.")]
public class AutoClassDataSourceAttribute : BaseDataSourceAttribute
{
    /// <summary>
    /// Initializes a new instance of the <see cref="AutoClassDataSourceAttribute"/> class.
    /// </summary>
    /// <param name="sourceType">The type of the class that provides the data.</param>
    /// <param name="parameters">The parameters passed to the data provider class constructor.</param>
    public AutoClassDataSourceAttribute(Type sourceType, params object?[] parameters)
        : this(() => new Fixture(), sourceType, parameters)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="AutoClassDataSourceAttribute"/> class.
    /// </summary>
    /// <param name="fixtureFactory">The fixture factory that provides missing data from <paramref name="sourceType"/>.</param>
    /// <param name="sourceType">The type of the class that provides the data.</param>
    /// <param name="parameters">The parameters passed to the data provider class constructor.</param>
    /// <para>
    /// This constructor overload exists to enable a derived attribute to
    /// supply a custom fixture factory that again may contain custom behavior.
    /// </para>
    /// <example>
    /// In the following example MyTestData is a class that provides test data,
    /// that would be complicated or probably impossible to provide using other options.
    /// The missing arguments for the test are being supplied from the Fixture instance.
    /// <code>
    /// [Test]
    /// [AutoClassDataSource(typeof(MyTestData))]
    /// public void ClassDataSuppliesExtraValues(int sum, int[] numbers, Person client)
    /// {
    ///     var actual = numbers.Sum(x => x);
    ///
    ///     Assert.Equal(sum, actual);
    ///     Assert.NotNull(client);
    /// }
    ///
    /// private class MyTestData : IEnumerable&lt;object?[]&gt;
    /// {
    ///     public IEnumerator&lt;object?[]&gt; GetEnumerator()
    ///     {
    ///         yield return new object?[] { 0, new int[0] };
    ///         yield return new object?[] { 4, new int[] { 1, 2, 1} };
    ///         yield return new object?[] { 23, new int [] { 0, 13, 15, -5 } };
    ///     }
    ///
    ///     IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
    /// }
    /// </code>
    /// </example>
    protected AutoClassDataSourceAttribute(Func<IFixture> fixtureFactory, Type sourceType, params object?[] parameters)
    {
        this.FixtureFactory = fixtureFactory ?? throw new ArgumentNullException(nameof(fixtureFactory));
        this.SourceType = sourceType ?? throw new ArgumentNullException(nameof(sourceType));
        this.Parameters = parameters ?? [null];
    }

    /// <summary>
    /// Gets the fixture factory that provides the missing data from <see cref="SourceType"/>.
    /// </summary>
    public Func<IFixture> FixtureFactory { get; }

    /// <summary>
    /// Gets the type of the class that provides the data.
    /// </summary>
    public Type SourceType { get; }

    /// <summary>
    /// Gets the constructor parameters for <see cref="SourceType"/>.
    /// </summary>
    public object?[] Parameters { get; }

    /// <inheritdoc />
    public override IEnumerable<object?[]> GetData(DataGeneratorMetadata dataGeneratorMetadata)
    {
        var source = new AutoDataSource(this.FixtureFactory,
            new ClassDataSource(this.SourceType, this.Parameters));

        return source.GetDataSources(dataGeneratorMetadata).Select(x => x());
    }
}