PowerShell · anmenaga · Feb 4, 2021 · Jan 12, 2021 · Jan 12, 2021 · Jan 13, 2021
diff --git a/src/System.Management.Automation/engine/Subsystem/CommandPrediction/CommandPrediction.cs b/src/System.Management.Automation/engine/Subsystem/CommandPrediction/CommandPrediction.cs
@@ -27,15 +27,22 @@ public sealed class PredictionResult
         /// </summary>
         public string Name { get; }
 
+        /// <summary>
+        /// Gets the mini-session id that represents a specific invocation to the <see cref="ICommandPredictor.GetSuggestion"/> API of the predictor.
+        /// When it's not specified, it's considered by a client that the predictor doesn't expect feedback.
+        /// </summary>
+        public uint? Session { get; }
+
         /// <summary>
         /// Gets the suggestions.
         /// </summary>
         public IReadOnlyList<PredictiveSuggestion> Suggestions { get; }
 
-        internal PredictionResult(Guid id, string name, List<PredictiveSuggestion> suggestions)
+        internal PredictionResult(Guid id, string name, uint? session, List<PredictiveSuggestion> suggestions)
         {
             Id = id;
             Name = name;
+            Session = session;
             Suggestions = suggestions;
         }
     }
@@ -48,22 +55,24 @@ public static class CommandPrediction
         /// <summary>
         /// Collect the predictive suggestions from registered predictors using the default timeout.
         /// </summary>
+        /// <param name="client">Represents the client that initiates the call.</param>
         /// <param name="ast">The <see cref="Ast"/> object from parsing the current command line input.</param>
         /// <param name="astTokens">The <see cref="Token"/> objects from parsing the current command line input.</param>
         /// <returns>A list of <see cref="PredictionResult"/> objects.</returns>
-        public static Task<List<PredictionResult>?> PredictInput(Ast ast, Token[] astTokens)
+        public static Task<List<PredictionResult>?> PredictInput(string client, Ast ast, Token[] astTokens)
         {
-            return PredictInput(ast, astTokens, millisecondsTimeout: 20);
+            return PredictInput(client, ast, astTokens, millisecondsTimeout: 20);
         }
 
         /// <summary>
         /// Collect the predictive suggestions from registered predictors using the specified timeout.
         /// </summary>
+        /// <param name="client">Represents the client that initiates the call.</param>
         /// <param name="ast">The <see cref="Ast"/> object from parsing the current command line input.</param>
         /// <param name="astTokens">The <see cref="Token"/> objects from parsing the current command line input.</param>
         /// <param name="millisecondsTimeout">The milliseconds to timeout.</param>
         /// <returns>A list of <see cref="PredictionResult"/> objects.</returns>
-        public static async Task<List<PredictionResult>?> PredictInput(Ast ast, Token[] astTokens, int millisecondsTimeout)
+        public static async Task<List<PredictionResult>?> PredictInput(string client, Ast ast, Token[] astTokens, int millisecondsTimeout)
         {
             Requires.Condition(millisecondsTimeout > 0, nameof(millisecondsTimeout));
 
@@ -85,8 +94,8 @@ public static class CommandPrediction
                     state =>
                     {
                         var predictor = (ICommandPredictor)state!;
-                        List<PredictiveSuggestion>? texts = predictor.GetSuggestion(context, cancellationSource.Token);
-                        return texts?.Count > 0 ? new PredictionResult(predictor.Id, predictor.Name, texts) : null;
+                        SuggestionPackage pkg = predictor.GetSuggestion(client, context, cancellationSource.Token);
+                        return pkg.SuggestionEntries?.Count > 0 ? new PredictionResult(predictor.Id, predictor.Name, pkg.Session, pkg.SuggestionEntries) : null;
                     },
                     predictor,
                     cancellationSource.Token,
@@ -99,27 +108,28 @@ await Task.WhenAny(
                 Task.Delay(millisecondsTimeout, cancellationSource.Token)).ConfigureAwait(false);
             cancellationSource.Cancel();
 
-            var results = new List<PredictionResult>(predictors.Count);
+            var resultList = new List<PredictionResult>(predictors.Count);
             foreach (Task<PredictionResult?> task in tasks)
             {
                 if (task.IsCompletedSuccessfully)
                 {
                     PredictionResult? result = task.Result;
                     if (result != null)
                     {
-                        results.Add(result);
+                        resultList.Add(result);
                     }
                 }
             }
 
-            return results;
+            return resultList;
         }
 
         /// <summary>
         /// Allow registered predictors to do early processing when a command line is accepted.
         /// </summary>
+        /// <param name="client">Represents the client that initiates the call.</param>
         /// <param name="history">History command lines provided as references for prediction.</param>
-        public static void OnCommandLineAccepted(IReadOnlyList<string> history)
+        public static void OnCommandLineAccepted(string client, IReadOnlyList<string> history)
         {
             Requires.NotNull(history, nameof(history));
 
@@ -134,19 +144,51 @@ public static void OnCommandLineAccepted(IReadOnlyList<string> history)
                 if (predictor.SupportEarlyProcessing)
                 {
                     ThreadPool.QueueUserWorkItem<ICommandPredictor>(
-                        state => state.StartEarlyProcessing(history),
+                        state => state.StartEarlyProcessing(client, history),
+                        predictor,
+                        preferLocal: false);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Send feedback to a predictor when one or more suggestions from it were displayed to the user.
+        /// </summary>
+        /// <param name="client">Represents the client that initiates the call.</param>
+        /// <param name="predictorId">The identifier of the predictor whose prediction result was accepted.</param>
+        /// <param name="session">The mini-session where the displayed suggestions came from.</param>
+        /// <param name="countOrIndex">
+        /// When the value is greater than 0, it's the number of displayed suggestions from the list returned in <paramref name="session"/>, starting from the index 0.
+        /// When the value is less than or equal to 0, it means a single suggestion from the list got displayed, and the index is the absolute value.
+        /// </param>
+        public static void OnSuggestionDisplayed(string client, Guid predictorId, uint session, int countOrIndex)
+        {
+            var predictors = SubsystemManager.GetSubsystems<ICommandPredictor>();
+            if (predictors.Count == 0)
+            {
+                return;
+            }
+
+            foreach (ICommandPredictor predictor in predictors)
+            {
+                if (predictor.AcceptFeedback && predictor.Id == predictorId)
+                {
+                    ThreadPool.QueueUserWorkItem<ICommandPredictor>(
+                        state => state.OnSuggestionDisplayed(client, session, countOrIndex),
                         predictor,
                         preferLocal: false);
                 }
             }
         }
 
         /// <summary>
-        /// Send feedback to predictors about their last suggestions.
+        /// Send feedback to a predictor when a suggestion from it was accepted.
         /// </summary>
+        /// <param name="client">Represents the client that initiates the call.</param>
         /// <param name="predictorId">The identifier of the predictor whose prediction result was accepted.</param>
+        /// <param name="session">The mini-session where the accepted suggestion came from.</param>
         /// <param name="suggestionText">The accepted suggestion text.</param>
-        public static void OnSuggestionAccepted(Guid predictorId, string suggestionText)
+        public static void OnSuggestionAccepted(string client, Guid predictorId, uint session, string suggestionText)
         {
             Requires.NotNullOrEmpty(suggestionText, nameof(suggestionText));
 
@@ -161,7 +203,7 @@ public static void OnSuggestionAccepted(Guid predictorId, string suggestionText)
                 if (predictor.AcceptFeedback && predictor.Id == predictorId)
                 {
                     ThreadPool.QueueUserWorkItem<ICommandPredictor>(
-                        state => state.OnSuggestionAccepted(suggestionText),
+                        state => state.OnSuggestionAccepted(client, session, suggestionText),
                         predictor,
                         preferLocal: false);
                 }

diff --git a/src/System.Management.Automation/engine/Subsystem/CommandPrediction/ICommandPredictor.cs b/src/System.Management.Automation/engine/Subsystem/CommandPrediction/ICommandPredictor.cs
@@ -40,22 +40,37 @@ public interface ICommandPredictor : ISubsystem
         /// A command line was accepted to execute.
         /// The predictor can start processing early as needed with the latest history.
         /// </summary>
+        /// <param name="clientId">Represents the client that initiates the call.</param>
         /// <param name="history">History command lines provided as references for prediction.</param>
-        void StartEarlyProcessing(IReadOnlyList<string> history);
+        void StartEarlyProcessing(string clientId, IReadOnlyList<string> history);
 
         /// <summary>
-        /// The suggestion given by the predictor was accepted.
+        /// Get the predictive suggestions. It indicates the start of a suggestion rendering session.
         /// </summary>
-        /// <param name="acceptedSuggestion">The accepted suggestion text.</param>
-        void OnSuggestionAccepted(string acceptedSuggestion);
+        /// <param name="clientId">Represents the client that initiates the call.</param>
+        /// <param name="context">The <see cref="PredictionContext"/> object to be used for prediction.</param>
+        /// <param name="cancellationToken">The cancellation token to cancel the prediction.</param>
+        /// <returns>An instance of <see cref="SuggestionPackage"/>.</returns>
+        SuggestionPackage GetSuggestion(string clientId, PredictionContext context, CancellationToken cancellationToken);
 
         /// <summary>
-        /// Get the predictive suggestions.
+        /// One or more suggestions provided by the predictor were displayed to the user.
         /// </summary>
-        /// <param name="context">The <see cref="PredictionContext"/> object to be used for prediction.</param>
-        /// <param name="cancellationToken">The cancellation token to cancel the prediction.</param>
-        /// <returns>A list of predictive suggestions.</returns>
-        List<PredictiveSuggestion>? GetSuggestion(PredictionContext context, CancellationToken cancellationToken);
+        /// <param name="clientId">Represents the client that initiates the call.</param>
+        /// <param name="session">The mini-session where the displayed suggestions came from.</param>
+        /// <param name="countOrIndex">
+        /// When the value is greater than 0, it's the number of displayed suggestions from the list returned in <paramref name="session"/>, starting from the index 0.
+        /// When the value is less than or equal to 0, it means a single suggestion from the list got displayed, and the index is the absolute value.
+        /// </param>
+        void OnSuggestionDisplayed(string clientId, uint session, int countOrIndex);
+
+        /// <summary>
+        /// The suggestion provided by the predictor was accepted.
+        /// </summary>
+        /// <param name="clientId">Represents the client that initiates the call.</param>
+        /// <param name="session">Represents the mini-session where the accepted suggestion came from.</param>
+        /// <param name="acceptedSuggestion">The accepted suggestion text.</param>
+        void OnSuggestionAccepted(string clientId, uint session, string acceptedSuggestion);
     }
 
     /// <summary>
@@ -160,4 +175,47 @@ public PredictiveSuggestion(string suggestion, string? toolTip)
             ToolTip = toolTip;
         }
     }
+
+    /// <summary>
+    /// A package returned from <see cref="ICommandPredictor.GetSuggestion"/>.
+    /// </summary>
+    public struct SuggestionPackage
+    {
+        /// <summary>
+        /// Gets the mini-session that represents a specific invocation to <see cref="ICommandPredictor.GetSuggestion"/>.
+        /// When it's not specified, it's considered by a client that the predictor doesn't expect feedback.
+        /// </summary>
+        public uint? Session { get; }
+
+        /// <summary>
+        /// Gets the suggestion entries returned from that mini-session.
+        /// </summary>
+        public List<PredictiveSuggestion>? SuggestionEntries { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SuggestionPackage"/> struct without providing a session id.
+        /// Note that, when a session id is not specified, it's considered by a client that the predictor doesn't expect feedback.
+        /// </summary>
+        /// <param name="suggestionEntries">The suggestions to return.</param>
+        public SuggestionPackage(List<PredictiveSuggestion> suggestionEntries)
+        {
+            Requires.NotNullOrEmpty(suggestionEntries, nameof(suggestionEntries));
+
+            Session = null;
+            SuggestionEntries = suggestionEntries;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SuggestionPackage"/> struct with the mini-session id and the suggestions.
+        /// </summary>
+        /// <param name="session">The mini-session where suggestions came from.</param>
+        /// <param name="suggestionEntries">The suggestions to return.</param>
+        public SuggestionPackage(uint session, List<PredictiveSuggestion> suggestionEntries)
+        {
+            Requires.NotNullOrEmpty(suggestionEntries, nameof(suggestionEntries));
+
+            Session = session;
+            SuggestionEntries = suggestionEntries;
+        }
+    }
 }
diff --git a/src/System.Management.Automation/engine/Utils.cs b/src/System.Management.Automation/engine/Utils.cs
@@ -2312,6 +2312,14 @@ internal static void NotNullOrEmpty(string value, string paramName)
             }
         }
 
+        internal static void NotNullOrEmpty(ICollection value, string paramName)
+        {
+            if (value == null || value.Count == 0)
+            {
+                throw new ArgumentNullException(paramName);
+            }
+        }
+
         internal static void Condition([DoesNotReturnIf(false)] bool precondition, string paramName)
         {
             if (!precondition)