Add basic support for inline predictive suggestion

PSReadLine/BasicEditing.cs

@@ -85,6 +85,8 @@ public static void CancelLine(ConsoleKeyInfo? key = null, object arg = null)
         {
             _singleton.ClearStatusMessage(false);
             _singleton._current = _singleton._buffer.Length;
+
+            using var _ = _singleton.PredictionOff();
             _singleton.ForceRender();
 
             _singleton._console.Write("\x1b[91m^C\x1b[0m");
@@ -214,6 +216,8 @@ public static void DeleteCharOrExit(ConsoleKeyInfo? key = null, object arg = nul
 
         private bool AcceptLineImpl(bool validate)
         {
+            using var _ = PredictionOff();
+
             ParseInput();
             if (_parseErrors.Any(e => e.IncompleteInput))
             {
@@ -274,6 +278,12 @@ private bool AcceptLineImpl(bool validate)
 
             // Let public API set cursor to end of line incase end of line is end of buffer
             SetCursorPosition(_current);
+            if (_suggestionText != null)
+            {
+                ResetSuggestion();
+                _console.BlankRestOfLine();
+            }
+
             _console.Write("\n");
             _inputAccepted = true;
             return true;

PSReadLine/Changes.txt

@@ -1,3 +1,9 @@
+### Version 2.1.0-beta1
+
+Pre-release notes:
+
+* Experimental support for fish-like suggestions in PSReadLine.
+
 ### Version 2.0.1
 
 Bug fixes:

PSReadLine/Cmdlets.cs

@@ -63,6 +63,12 @@ public enum AddToHistoryOption
         MemoryAndFile
     }
 
+    public enum PredictionSource
+    {
+        None,
+        History,
+    }
+
     public class PSConsoleReadLineOptions
     {
         public const ConsoleColor DefaultCommentColor   = ConsoleColor.DarkGreen;
@@ -78,6 +84,10 @@ public class PSConsoleReadLineOptions
         public const ConsoleColor DefaultEmphasisColor  = ConsoleColor.Cyan;
         public const ConsoleColor DefaultErrorColor     = ConsoleColor.Red;
 
+        // Use dark black by default for the suggestion text.
+        // Find the most suitable color using https://stackoverflow.com/a/33206814
+        public const string DefaultPredictionColor = "\x1b[38;5;238m";
+
         public static EditMode DefaultEditMode = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
             ? EditMode.Windows
             : EditMode.Emacs;
@@ -128,6 +138,11 @@ public class PSConsoleReadLineOptions
 
         public const HistorySaveStyle DefaultHistorySaveStyle = HistorySaveStyle.SaveIncrementally;
 
+        /// <summary>
+        /// The predictive suggestion feature is disabled by default.
+        /// </summary>
+        public const PredictionSource DefaultPredictionSource = PredictionSource.None;
+
         /// <summary>
         /// How long in milliseconds should we wait before concluding
         /// the input is not an escape sequence?
@@ -155,6 +170,7 @@ public PSConsoleReadLineOptions(string hostName)
             HistorySearchCaseSensitive = DefaultHistorySearchCaseSensitive;
             HistorySaveStyle = DefaultHistorySaveStyle;
             AnsiEscapeTimeout = DefaultAnsiEscapeTimeout;
+            PredictionSource = DefaultPredictionSource;
 
             var historyFileName = hostName + "_history.txt";
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
@@ -309,6 +325,11 @@ public object ContinuationPromptColor
         public string HistorySavePath { get; set; }
         public HistorySaveStyle HistorySaveStyle { get; set; }
 
+        /// <summary>
+        /// Sets the source to get predictive suggestions.
+        /// </summary>
+        public PredictionSource PredictionSource { get; set; }
+
         /// <summary>
         /// How long in milliseconds should we wait before concluding
         /// the input is not an escape sequence?
@@ -407,6 +428,12 @@ public object SelectionColor
             set => _selectionColor = VTColorUtils.AsEscapeSequence(value);
         }
 
+        public object PredictionColor
+        {
+            get => _predictionColor;
+            set => _predictionColor = VTColorUtils.AsEscapeSequence(value);
+        }
+
         internal string _defaultTokenColor;
         internal string _commentColor;
         internal string _keywordColor;
@@ -421,6 +448,7 @@ public object SelectionColor
         internal string _emphasisColor;
         internal string _errorColor;
         internal string _selectionColor;
+        internal string _predictionColor;
 
         internal void ResetColors()
         {
@@ -438,6 +466,7 @@ internal void ResetColors()
             MemberColor       = DefaultNumberColor;
             EmphasisColor     = DefaultEmphasisColor;
             ErrorColor        = DefaultErrorColor;
+            PredictionColor   = DefaultPredictionColor;
 
             var bg = Console.BackgroundColor;
             if (fg == VTColorUtils.UnknownColor || bg == VTColorUtils.UnknownColor)
@@ -473,7 +502,8 @@ internal void SetColor(string property, object value)
                         {"Type", (o, v) => o.TypeColor = v},
                         {"Number", (o, v) => o.NumberColor = v},
                         {"Member", (o, v) => o.MemberColor = v},
-                        {"Selection", (o, v) => o.SelectionColor = v },
+                        {"Selection", (o, v) => o.SelectionColor = v},
+                        {"Prediction", (o, v) => o.PredictionColor = v},
                     };
 
                 Interlocked.CompareExchange(ref ColorSetters, setters, null);
@@ -680,6 +710,14 @@ public ViModeStyle ViModeIndicator
         [Parameter]
         public ScriptBlock ViModeChangeHandler { get; set; }
 
+        [Parameter]
+        public PredictionSource PredictionSource
+        {
+            get => _predictionSource.GetValueOrDefault();
+            set => _predictionSource = value;
+        }
+        internal PredictionSource? _predictionSource;
+
         [Parameter]
         public Hashtable Colors { get; set; }
 

PSReadLine/Completion.cs

@@ -217,6 +217,9 @@ private void CompleteImpl(bool menuSelect)
                 ViInsertWithAppend();
             }
 
+            // Do not show suggestion text during tab completion.
+            using var _ = PredictionOff();
+
             var completions = GetCompletions();
             if (completions == null || completions.CompletionMatches.Count == 0)
                 return;

PSReadLine/History.cs

@@ -502,6 +502,8 @@ private void UpdateFromHistory(HistoryMoveCursor moveCursor)
                     }
                     break;
             }
+
+            using var _ = PredictionOff();
             Render();
         }
 
@@ -677,6 +679,30 @@ private void HistorySearch(int direction)
             }
         }
 
+        /// <summary>
+        /// Currently we only select single-line history that is prefixed with the user input,
+        /// but it can be improved to not strictly use the user input as a prefix, but a hint
+        /// to extract a partial pipeline or statement from a single-line or multiple-line
+        /// history entry.
+        /// </summary>
+        private string GetHistorySuggestion(string text)
+        {
+            for (int index = _history.Count - 1; index >= 0; index --)
+            {
+                var line = _history[index].CommandLine.TrimEnd();
+                if (line.Length > text.Length)
+                {
+                    bool isMultiLine = line.Contains('\n');
+                    if (!isMultiLine && line.StartsWith(text, Options.HistoryStringComparison))
+                    {
+                        return line;
+                    }
+                }
+            }
+
+            return null;
+        }
+
         /// <summary>
         /// Move to the first item in the history.
         /// </summary>
@@ -889,6 +915,7 @@ private void InteractiveHistorySearchLoop(int direction)
 
         private void InteractiveHistorySearch(int direction)
         {
+            using var _ = PredictionOff();
             SaveCurrentLine();
 
             // Add a status line that will contain the search prompt and string

PSReadLine/KeyBindings.cs

@@ -549,6 +549,8 @@ public static KeyHandlerGroup GetDisplayGrouping(string function)
             case nameof(ViExit):
             case nameof(ViInsertMode):
             case nameof(WhatIsKey):
+            case nameof(AcceptSuggestion):
+            case nameof(AcceptNextSuggestionWord):
                 return KeyHandlerGroup.Miscellaneous;
 
             case nameof(CharacterSearch):

PSReadLine/Movement.cs

@@ -61,7 +61,14 @@ public static void ForwardChar(ConsoleKeyInfo? key = null, object arg = null)
         {
             if (TryGetArgAsInt(arg, out var numericArg, 1))
             {
-                SetCursorPosition(_singleton._current + numericArg);
+                if (_singleton._current == _singleton._buffer.Length && numericArg > 0)
+                {
+                    AcceptSuggestion(key, arg);
+                }
+                else
+                {
+                    SetCursorPosition(_singleton._current + numericArg);
+                }
             }
         }
 
@@ -311,6 +318,12 @@ public static void ForwardWord(ConsoleKeyInfo? key = null, object arg = null)
                 return;
             }
 
+            if (_singleton._current == _singleton._buffer.Length && numericArg > 0)
+            {
+                AcceptNextSuggestionWord(numericArg);
+                return;
+            }
+
             if (numericArg < 0)
             {
                 BackwardWord(key, -numericArg);

PSReadLine/Options.cs

@@ -135,6 +135,14 @@ private void SetOptionsInternal(SetPSReadLineOption options)
             {
                 Options.PromptText = options.PromptText;
             }
+            if (options._predictionSource.HasValue)
+            {
+                if (_console is PlatformWindows.LegacyWin32Console && options.PredictionSource != PredictionSource.None)
+                {
+                    throw new ArgumentException(PSReadLineResources.PredictiveSuggestionNotSupported);
+                }
+                Options.PredictionSource = options.PredictionSource;
+            }
             if (options.Colors != null)
             {
                 IDictionaryEnumerator e = options.Colors.GetEnumerator();

PSReadLine/PSReadLine.csproj

@@ -4,11 +4,12 @@
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.PowerShell.PSReadLine</RootNamespace>
     <AssemblyName>Microsoft.PowerShell.PSReadLine2</AssemblyName>
-    <AssemblyVersion>2.0.1.0</AssemblyVersion>
-    <FileVersion>2.0.1</FileVersion>
-    <InformationalVersion>2.0.1</InformationalVersion>
+    <AssemblyVersion>2.1.0.0</AssemblyVersion>
+    <FileVersion>2.1.0</FileVersion>
+    <InformationalVersion>2.1.0-beta1</InformationalVersion>
     <CheckForOverflowUnderflow>true</CheckForOverflowUnderflow>
     <TargetFrameworks>net461;netcoreapp2.1</TargetFrameworks>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.1'">

PSReadLine/PSReadLine.format.ps1xml

@@ -158,6 +158,9 @@ $d = [Microsoft.PowerShell.KeyHandler]::GetGroupingDescription($_.Group)
               <ListItem>
                 <PropertyName>AnsiEscapeTimeout</PropertyName>
               </ListItem>
+              <ListItem>
+                <PropertyName>PredictionSource</PropertyName>
+              </ListItem>
               <ListItem>
                 <Label>CommandColor</Label>
                 <ScriptBlock>[Microsoft.PowerShell.VTColorUtils]::FormatColor($_.CommandColor)</ScriptBlock>
@@ -202,6 +205,10 @@ $d = [Microsoft.PowerShell.KeyHandler]::GetGroupingDescription($_.Group)
                 <Label>ParameterColor</Label>
                 <ScriptBlock>[Microsoft.PowerShell.VTColorUtils]::FormatColor($_.ParameterColor)</ScriptBlock>
               </ListItem>
+              <ListItem>
+                <Label>PredictionColor</Label>
+                <ScriptBlock>[Microsoft.PowerShell.VTColorUtils]::FormatColor($_.PredictionColor)</ScriptBlock>
+              </ListItem>
               <ListItem>
                 <Label>SelectionColor</Label>
                 <ScriptBlock>[Microsoft.PowerShell.VTColorUtils]::FormatColor($_.SelectionColor)</ScriptBlock>

PSReadLine/PSReadLineResources.resx

@@ -741,6 +741,12 @@ If there are other parse errors, unresolved commands, or incorrect parameters, s
   <data name="InsertLineBelowDescription" xml:space="preserve">
     <value>Inserts a new empty line below the current line without attempting to execute the input</value>
   </data>
+  <data name="AcceptSuggestionDescription" xml:space="preserve">
+    <value>Accept the current inline or selected suggestion</value>
+  </data>
+  <data name="AcceptNextSuggestionWordDescription" xml:space="preserve">
+    <value>Accept the next word of the inline or selected suggestion</value>
+  </data>
   <data name="HistoryFileErrorMessage" xml:space="preserve">
     <value>Error reading or writing history file '{0}': {1}</value>
   </data>
@@ -783,4 +789,7 @@ Or not saving history with:
   <data name="InvalidColorProperty" xml:space="preserve">
     <value>'{0}' is not a valid color property</value>
   </data>
+  <data name="PredictiveSuggestionNotSupported" xml:space="preserve">
+    <value>The predictive suggestion feature cannot be enabled because the console output doesn't support virtual terminal processing or it's redirected.</value>
+  </data>
 </root>

PSReadLine/ReadLine.vi.cs

@@ -522,6 +522,9 @@ internal static IDisposable UseViInsertModeTables()
 
         private void ViIndicateCommandMode()
         {
+            // Show suggestion in 'InsertMode' but not 'CommandMode'.
+            _showSuggestion = false;
+
             if (_options.ViModeIndicator == ViModeStyle.Cursor)
             {
                 _console.CursorSize = _normalCursorSize < 50 ? 100 : 25;
@@ -541,6 +544,9 @@ private void ViIndicateCommandMode()
 
         private void ViIndicateInsertMode()
         {
+            // Show suggestion in 'InsertMode' but not 'CommandMode'.
+            _showSuggestion = true;
+
             if (_options.ViModeIndicator == ViModeStyle.Cursor)
             {
                 _console.CursorSize = _normalCursorSize;