dotnet/src/webdriver/Support/DefaultWait{T}.cs

// <copyright file="DefaultWait{T}.cs" company="Selenium Committers">
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
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using System.Diagnostics.CodeAnalysis;
using System.Globalization;

namespace OpenQA.Selenium.Support.UI;

/// <summary>
/// An implementation of the <see cref="IWait&lt;T&gt;"/> interface that may have its timeout and polling interval
/// configured on the fly.
/// </summary>
/// <typeparam name="T">The type of object on which the wait it to be applied.</typeparam>
public class DefaultWait<T> : IWait<T>
{
    private readonly T input;
    private readonly IClock clock;
    private readonly List<Type> ignoredExceptions = new List<Type>();

    /// <summary>
    /// Initializes a new instance of the <see cref="DefaultWait&lt;T&gt;"/> class.
    /// </summary>
    /// <param name="input">The input value to pass to the evaluated conditions.</param>
    public DefaultWait(T input)
        : this(input, SystemClock.Instance)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="DefaultWait&lt;T&gt;"/> class.
    /// </summary>
    /// <param name="input">The input value to pass to the evaluated conditions.</param>
    /// <param name="clock">The clock to use when measuring the timeout.</param>
    /// <exception cref="ArgumentNullException">If <paramref name="clock"/> or <paramref name="input"/> are <see langword="null"/>.</exception>
    public DefaultWait(T input, IClock clock)
    {
        this.input = input ?? throw new ArgumentNullException(nameof(input), "input cannot be null"); ;
        this.clock = clock ?? throw new ArgumentNullException(nameof(clock), "clock cannot be null"); ;
    }

    /// <summary>
    /// Gets or sets how long to wait for the evaluated condition to be true. The default timeout is 500 milliseconds.
    /// </summary>
    public TimeSpan Timeout { get; set; } = DefaultSleepTimeout;

    /// <summary>
    /// Gets or sets how often the condition should be evaluated. The default timeout is 500 milliseconds.
    /// </summary>
    public TimeSpan PollingInterval { get; set; } = DefaultSleepTimeout;

    /// <summary>
    /// Gets or sets the message to be displayed when time expires.
    /// </summary>
    public string Message { get; set; } = string.Empty;

    private static TimeSpan DefaultSleepTimeout => TimeSpan.FromMilliseconds(500);

    /// <summary>
    /// Configures this instance to ignore specific types of exceptions while waiting for a condition.
    /// Any exceptions not whitelisted will be allowed to propagate, terminating the wait.
    /// </summary>
    /// <param name="exceptionTypes">The types of exceptions to ignore.</param>
    public void IgnoreExceptionTypes(params Type[] exceptionTypes)
    {
        if (exceptionTypes == null)
        {
            throw new ArgumentNullException(nameof(exceptionTypes), "exceptionTypes cannot be null");
        }

        foreach (Type exceptionType in exceptionTypes)
        {
            if (!typeof(Exception).IsAssignableFrom(exceptionType))
            {
                throw new ArgumentException("All types to be ignored must derive from System.Exception", nameof(exceptionTypes));
            }
        }

        this.ignoredExceptions.AddRange(exceptionTypes);
    }

    /// <summary>
    /// Repeatedly applies this instance's input value to the given function until one of the following
    /// occurs:
    /// <para>
    /// <list type="bullet">
    /// <item>the function returns neither null nor false</item>
    /// <item>the function throws an exception that is not in the list of ignored exception types</item>
    /// <item>the timeout expires</item>
    /// </list>
    /// </para>
    /// </summary>
    /// <typeparam name="TResult">The delegate's expected return type.</typeparam>
    /// <param name="condition">A delegate taking an object of type T as its parameter, and returning a TResult.</param>
    /// <returns>The delegate's return value.</returns>
    [return: NotNull]
    public virtual TResult Until<TResult>(Func<T, TResult?> condition)
    {
        return Until(condition, CancellationToken.None);
    }

    /// <summary>
    /// Repeatedly applies this instance's input value to the given function until one of the following
    /// occurs:
    /// <para>
    /// <list type="bullet">
    /// <item>the function returns neither null nor false</item>
    /// <item>the function throws an exception that is not in the list of ignored exception types</item>
    /// <item>the timeout expires</item>
    /// </list>
    /// </para>
    /// </summary>
    /// <typeparam name="TResult">The delegate's expected return type.</typeparam>
    /// <param name="condition">A delegate taking an object of type T as its parameter, and returning a TResult.</param>
    /// <param name="token">A cancellation token that can be used to cancel the wait.</param>
    /// <returns>The delegate's return value.</returns>
    [return: NotNull]
    public virtual TResult Until<TResult>(Func<T, TResult?> condition, CancellationToken token)
    {
        if (condition == null)
        {
            throw new ArgumentNullException(nameof(condition), "condition cannot be null");
        }

        var resultType = typeof(TResult);
        if ((resultType.IsValueType && resultType != typeof(bool)) || !typeof(object).IsAssignableFrom(resultType))
        {
            throw new ArgumentException($"Can only wait on an object or boolean response, tried to use type: {resultType}", nameof(condition));
        }

        Exception? lastException = null;
        var endTime = this.clock.LaterBy(this.Timeout);
        while (true)
        {
            token.ThrowIfCancellationRequested();

            try
            {
                var result = condition(this.input);
                if (resultType == typeof(bool))
                {
                    if (result is true)
                    {
                        return result;
                    }
                }
                else
                {
                    if (result != null)
                    {
                        return result;
                    }
                }
            }
            catch (Exception ex)
            {
                if (!this.IsIgnoredException(ex))
                {
                    throw;
                }

                lastException = ex;
            }

            // Check the timeout after evaluating the function to ensure conditions
            // with a zero timeout can succeed.
            if (!this.clock.IsNowBefore(endTime))
            {
                string timeoutMessage = string.Format(CultureInfo.InvariantCulture, "Timed out after {0} seconds", this.Timeout.TotalSeconds);
                if (!string.IsNullOrEmpty(this.Message))
                {
                    timeoutMessage += ": " + this.Message;
                }

                this.ThrowTimeoutException(timeoutMessage, lastException);
            }

            Thread.Sleep(this.PollingInterval);
        }
    }

    /// <summary>
    /// Throws a <see cref="WebDriverTimeoutException"/> with the given message.
    /// </summary>
    /// <param name="exceptionMessage">The message of the exception.</param>
    /// <param name="lastException">The last exception thrown by the condition.</param>
    /// <remarks>This method may be overridden to throw an exception that is
    /// idiomatic for a particular test infrastructure.</remarks>
    protected virtual void ThrowTimeoutException(string exceptionMessage, Exception? lastException)
    {
        throw new WebDriverTimeoutException(exceptionMessage, lastException);
    }

    private bool IsIgnoredException(Exception exception)
    {
        return this.ignoredExceptions.Any(type => type.IsAssignableFrom(exception.GetType()));
    }
}