Add the "Dynamic Help" feature to PSReadLine (#1777)

- Adds a way to view help on alternate screen buffer for full help and uses a Pager from `Microsoft.PowerShell.Pager`.
- Implements dynamic help for parameters by showing it below the current command line like `MenuComplete`.

Author: adityapatwardhan

.vsts-ci/releaseBuild.yml

@@ -76,6 +76,7 @@ stages:
           *.ps1xml
           **\*.dll
           !System.Runtime.InteropServices.RuntimeInformation.dll
+          !Microsoft.PowerShell.Pager.dll
         useMinimatch: true
 
     # Replace the *.psm1, *.ps1, *.psd1, *.dll files with the signed ones

MockPSConsole/MockPSConsole.csproj

@@ -18,7 +18,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net5.0'">
-    <PackageReference Include="Microsoft.PowerShell.SDK" version="7.1.0-rc.2" />
+    <PackageReference Include="Microsoft.PowerShell.SDK" version="7.1.0" />
   </ItemGroup>
 
   <ItemGroup>

PSReadLine.build.ps1

@@ -142,6 +142,7 @@ task LayoutModule BuildPolyfiller, BuildMainModule, {
 
     $binPath = "PSReadLine/bin/$Configuration/$Framework/publish"
     Copy-Item $binPath/Microsoft.PowerShell.PSReadLine2.dll $targetDir
+    Copy-Item $binPath/Microsoft.PowerShell.Pager.dll $targetDir
 
     if (Test-Path $binPath/System.Runtime.InteropServices.RuntimeInformation.dll) {
         Copy-Item $binPath/System.Runtime.InteropServices.RuntimeInformation.dll $targetDir

PSReadLine/Completion.cs

@@ -422,17 +422,15 @@ private static string HandleNewlinesForPossibleCompletions(string s)
             return s;
         }
 
-        private class Menu
+        private class Menu : DisplayBlockBase
         {
-            internal PSConsoleReadLine Singleton;
-            internal int Top;
-
             internal int PreviousTop;
             internal int ColumnWidth;
             internal int BufferLines;
             internal int Rows;
             internal int Columns;
             internal int ToolTipLines;
+
             internal Collection<CompletionResult> MenuItems;
             internal CompletionResult CurrentMenuItem => MenuItems[CurrentSelection];
             internal int CurrentSelection;
@@ -701,39 +699,6 @@ public void MoveN(int n)
                     CurrentSelection += MenuItems.Count;
                 }
             }
-
-            private void MoveCursorDown(int cnt)
-            {
-                IConsole console = Singleton._console;
-                while (cnt-- > 0)
-                {
-                    console.Write("\n");
-                }
-            }
-
-            private void AdjustForPossibleScroll(int cnt)
-            {
-                IConsole console = Singleton._console;
-                var scrollCnt = console.CursorTop + cnt + 1 - console.BufferHeight;
-                if (scrollCnt > 0)
-                {
-                    Top -= scrollCnt;
-                    _singleton._initialY -= scrollCnt;
-                    _savedCursorTop -= scrollCnt;
-                }
-            }
-
-            private int _savedCursorLeft;
-            private int _savedCursorTop;
-
-            public void SaveCursor()
-            {
-                IConsole console = Singleton._console;
-                _savedCursorLeft = console.CursorLeft;
-                _savedCursorTop = console.CursorTop;
-            }
-
-            public void RestoreCursor() => Singleton._console.SetCursorPosition(_savedCursorLeft, _savedCursorTop);
         }
 
         private Menu CreateCompletionMenu(Collection<CompletionResult> matches)

PSReadLine/DisplayBlockBase.cs

@@ -0,0 +1,51 @@
+/********************************************************************++
+Copyright (c) Microsoft Corporation.  All rights reserved.
+--********************************************************************/
+
+using System;
+using Microsoft.PowerShell.Internal;
+
+namespace Microsoft.PowerShell
+{
+    public partial class PSConsoleReadLine
+    {
+        private class DisplayBlockBase
+        {
+            internal PSConsoleReadLine Singleton;
+            internal int Top;
+
+            protected void MoveCursorDown(int cnt)
+            {
+                IConsole console = Singleton._console;
+                while (cnt-- > 0)
+                {
+                    console.Write("\n");
+                }
+            }
+
+            protected void AdjustForPossibleScroll(int cnt)
+            {
+                IConsole console = Singleton._console;
+                var scrollCnt = console.CursorTop + cnt + 1 - console.BufferHeight;
+                if (scrollCnt > 0)
+                {
+                    Top -= scrollCnt;
+                    _singleton._initialY -= scrollCnt;
+                    _savedCursorTop -= scrollCnt;
+                }
+            }
+
+            private int _savedCursorLeft;
+            private int _savedCursorTop;
+
+            public void SaveCursor()
+            {
+                IConsole console = Singleton._console;
+                _savedCursorLeft = console.CursorLeft;
+                _savedCursorTop = console.CursorTop;
+            }
+
+            public void RestoreCursor() => Singleton._console.SetCursorPosition(_savedCursorLeft, _savedCursorTop);
+        }
+    }
+}