Accept -i for an interactive shell (#3558)

On Unix, it is a convention for shells to accept `-i` for an interactive shell and many
tools expect this behavior (`script` for example, and when setting powershell as the
default shell) and calls the shell with the `-i` switch.  This change is breaking in
that `-i` previously could be used as short hand to match `-inputformat` which now will
need to be `-in`.

src/Microsoft.PowerShell.ConsoleHost/host/msh/CommandLineParameterParser.cs

@@ -570,6 +570,10 @@ namespace Microsoft.PowerShell
                 {
                     _sshServerMode = true;
                 }
+                else if (MatchSwitch(switchKey, "interactive", "i"))
+                {
+                    _noInteractive = false;
+                }
                 else if (MatchSwitch(switchKey, "configurationname", "config"))
                 {
                     ++i;
@@ -801,7 +805,7 @@ namespace Microsoft.PowerShell
                 {
                     ParseFormat(args, ref i, ref _outFormat, CommandLineParameterParserStrings.MissingOutputFormatParameter);
                 }
-                else if (MatchSwitch(switchKey, "inputformat", "i") || MatchSwitch(switchKey, "if", "i"))
+                else if (MatchSwitch(switchKey, "inputformat", "in") || MatchSwitch(switchKey, "if", "if"))
                 {
                     ParseFormat(args, ref i, ref _inFormat, CommandLineParameterParserStrings.MissingInputFormatParameter);
                 }

src/Microsoft.PowerShell.ConsoleHost/resources/ManagedEntranceStrings.resx

@@ -127,7 +127,7 @@ Copyright (C) Microsoft Corporation. All rights reserved.</value>
   </data>
   <data name="ShellHelp" xml:space="preserve">
     <value>PowerShell[.exe] [-PSConsoleFile &lt;file&gt; | -Version &lt;version&gt;]
-    [-NoLogo] [-NoExit] [-Sta] [-Mta] [-NoProfile] [-NonInteractive]
+    [-NoLogo] [-NoExit] [-Sta] [-Mta] [-NoProfile] [-NonInteractive] [-Interactive]
     [-InputFormat {Text | XML}] [-OutputFormat {Text | XML}]
     [-WindowStyle &lt;style&gt;] [-EncodedCommand &lt;Base64EncodedCommand&gt;]
     [-ConfigurationName &lt;string&gt;]
@@ -164,6 +164,9 @@ PowerShell[.exe] -Help | -? | /?
 -NonInteractive
     Does not present an interactive prompt to the user.
 
+-Interactive
+    Present an interactive prompt to the user.
+
 -InputFormat
     Describes the format of data sent to Windows PowerShell. Valid values are
     "Text" (text strings) or "XML" (serialized CLIXML format).

test/powershell/Host/ConsoleHost.Tests.ps1

@@ -267,8 +267,13 @@ Describe "ConsoleHost unit tests" -tags "Feature" {
         # All of the following tests replace the prompt (either via an initial command or interactively)
         # so that we can read StandardOutput and reliably know exactly what the prompt is.
 
-        It "Interactive redirected input" {
-            $si = NewProcessStartInfo "-noprofile -nologo" -RedirectStdIn
+        It "Interactive redirected input" -TestCases @(
+            @{InteractiveSwitch = ""}
+            @{InteractiveSwitch = " -IntERactive"}
+            @{InteractiveSwitch = " -i"}
+        ) {
+            param($interactiveSwitch)
+            $si = NewProcessStartInfo "-noprofile -nologo$interactiveSwitch" -RedirectStdIn
             $process = RunPowerShell $si
             $process.StandardInput.Write("`$function:prompt = { 'PS> ' }`n")
             $null = $process.StandardOutput.ReadLine()