Fix stdin locking on Unix platforms

Wait for Console.KeyAvailable before calling Console.ReadKey so getting
cursor position doesn't block the thread.

Author: SeeminglyScience

PSReadLine.build.ps1

@@ -202,6 +202,9 @@ task LayoutModule BuildMainModule, BuildMamlHelp, {
 
     Copy-Item PSReadLine/bin/$Configuration/Microsoft.PowerShell.PSReadLine2.dll $targetDir
     Copy-Item PSReadLine/bin/$Configuration/System.Runtime.InteropServices.RuntimeInformation.dll $targetDir
+    Copy-Item PSReadLine/bin/$Configuration/UnixConsoleEcho.dll $targetDir
+    Copy-Item PSReadLine/bin/$Configuration/libdisablekeyecho.so $targetDir
+    Copy-Item PSReadLine/bin/$Configuration/libdisablekeyecho.dylib $targetDir
 
     # Copy module manifest, but fix the version to match what we've specified in the binary module.
     $version = (Get-ChildItem -Path $targetDir/Microsoft.PowerShell.PSReadLine2.dll).VersionInfo.FileVersion

PSReadLine/ConsoleLib.cs

@@ -97,7 +97,32 @@ public Encoding OutputEncoding
             set { try { Console.OutputEncoding = value; } catch { } }
         }
 
-        public ConsoleKeyInfo ReadKey()                  => Console.ReadKey(true);
+        private void WaitForKeyAvailable()
+        {
+            // On Unix platforms input echo is on by default. If we wait for KeyAvailable without
+            // disabling it, all input will be echoed.
+            UnixConsoleEcho.InputEcho.Disable();
+            try
+            {
+                while (!Console.KeyAvailable)
+                {
+                    System.Threading.Thread.Sleep(50);
+                }
+            }
+            finally
+            {
+                UnixConsoleEcho.InputEcho.Enable();
+            }
+        }
+
+        public ConsoleKeyInfo ReadKey()
+        {
+            // Wait for a key to be pressed before calling ReadKey to avoid locking stdin on
+            // non-Windows platforms.
+            WaitForKeyAvailable();
+            return Console.ReadKey(true);
+        }
+
         public bool KeyAvailable                         => Console.KeyAvailable;
         public void SetWindowPosition(int left, int top) => Console.SetWindowPosition(left, top);
         public void SetCursorPosition(int left, int top) => Console.SetCursorPosition(left, top);

PSReadLine/PSReadLine.csproj

@@ -51,6 +51,9 @@
     <Reference Include="Microsoft.CSharp" />
     <Reference Include="System.Data" />
     <Reference Include="System.Xml" />
+    <Reference Include="UnixConsoleEcho, Version=1.0.0.0, Culture=neutral, processorArchitecture=MSIL">
+      <HintPath>packages\UnixConsoleEcho.0.1.0\lib\net461\UnixConsoleEcho.dll</HintPath>
+    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="AssemblyInfo.cs" />
@@ -121,6 +124,13 @@
     ..\..\CopyDLL.cmd $(TargetPath)
 )</PostBuildEvent>
   </PropertyGroup>
+  <Import Project="packages\UnixConsoleEcho.0.1.0\build\net461\UnixConsoleEcho.targets" Condition="Exists('packages\UnixConsoleEcho.0.1.0\build\net461\UnixConsoleEcho.targets')" />
+  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
+    <PropertyGroup>
+      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
+    </PropertyGroup>
+    <Error Condition="!Exists('packages\UnixConsoleEcho.0.1.0\build\net461\UnixConsoleEcho.targets')" Text="$([System.String]::Format('$(ErrorText)', 'packages\UnixConsoleEcho.0.1.0\build\net461\UnixConsoleEcho.targets'))" />
+  </Target>
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">

PSReadLine/packages.config

@@ -2,4 +2,5 @@
 <packages>
   <package id="Microsoft.PowerShell.5.ReferenceAssemblies" version="1.0.0" targetFramework="net461" />
   <package id="System.Runtime.InteropServices.RuntimeInformation" version="4.3.0" targetFramework="net461" />
+  <package id="UnixConsoleEcho" version="0.1.0" targetFramework="net461" />
 </packages>