Bring back the code that shares output binding metadata with the helper module (Azure#161)

When script from the helper module is running, it can use `[FuncMetadata]::GetOutputBindingInfo([Runspace]::DefaultRunspace.InstanceId)` to get the output binding info about the function that is currently running. Hence, `Push-OutputBinidng` can do smart things based on the `-Name` with this change.

Author: daxian-dbw

build.ps1

@@ -42,7 +42,7 @@ if ($Bootstrap.IsPresent) {
 # Clean step
 if($Clean.IsPresent) {
     Push-Location $PSScriptRoot
-    git clean -fdx
+    git clean -fdX
     Pop-Location
 }
 

src/PowerShell/PowerShellManager.cs

@@ -23,6 +23,11 @@ internal class PowerShellManager
         private readonly ILogger _logger;
         private readonly PowerShell _pwsh;
 
+        /// <summary>
+        /// Gets the Runspace InstanceId.
+        /// </summary>
+        internal Guid InstanceId => _pwsh.Runspace.InstanceId;
+
         /// <summary>
         /// Gets the associated logger.
         /// </summary>

src/PowerShell/PowerShellManagerPool.cs

@@ -90,6 +90,8 @@ internal PowerShellManager CheckoutIdleWorker(StreamingMessage request, AzFuncti
                 }
             }
 
+            // Register the function with the Runspace before returning the idle PowerShellManager.
+            FunctionMetadata.RegisterFunctionMetadata(psManager.InstanceId, functionInfo);
             psManager.Logger.SetContext(requestId, invocationId);
             return psManager;
         }
@@ -101,6 +103,8 @@ internal void ReclaimUsedWorker(PowerShellManager psManager)
         {
             if (psManager != null)
             {
+                // Unregister the Runspace before reclaiming the used PowerShellManager.
+                FunctionMetadata.UnregisterFunctionMetadata(psManager.InstanceId);
                 psManager.Logger.ResetContext();
                 _pool.Add(psManager);
             }

src/Public/FunctionMetadata.cs

@@ -0,0 +1,47 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.ObjectModel;
+
+namespace Microsoft.Azure.Functions.PowerShellWorker
+{
+    /// <summary>
+    /// Function metadata for the PowerShellWorker module to query.
+    /// </summary>
+    public static class FunctionMetadata
+    {
+        internal static ConcurrentDictionary<Guid, ReadOnlyDictionary<string, ReadOnlyBindingInfo>> OutputBindingCache
+            = new ConcurrentDictionary<Guid, ReadOnlyDictionary<string, ReadOnlyBindingInfo>>();
+
+        /// <summary>
+        /// Get the binding metadata for the given Runspace instance id.
+        /// </summary>
+        public static ReadOnlyDictionary<string, ReadOnlyBindingInfo> GetOutputBindingInfo(Guid runspaceInstanceId)
+        {
+            ReadOnlyDictionary<string, ReadOnlyBindingInfo> outputBindings = null;
+            OutputBindingCache.TryGetValue(runspaceInstanceId, out outputBindings);
+            return outputBindings;
+        }
+
+        /// <summary>
+        /// Helper method to set the output binding metadata for the function that is about to run.
+        /// </summary>
+        internal static void RegisterFunctionMetadata(Guid instanceId, AzFunctionInfo functionInfo)
+        {
+            var outputBindings = functionInfo.OutputBindings;
+            OutputBindingCache.AddOrUpdate(instanceId, outputBindings, (key, value) => outputBindings);
+        }
+
+        /// <summary>
+        /// Helper method to clear the output binding metadata for the function that has done running.
+        /// </summary>
+        internal static void UnregisterFunctionMetadata(Guid instanceId)
+        {
+            OutputBindingCache.TryRemove(instanceId, out _);
+        }
+    }
+}

test/Unit/PowerShell/PowerShellManagerTests.cs

@@ -152,6 +152,19 @@ public void ModulePathShouldBeSetCorrectly()
             Assert.Equal(expectedPath, Environment.GetEnvironmentVariable("PSModulePath"));
         }
 
+        [Fact]
+        public void RegisterAndUnregisterFunctionMetadataShouldWork()
+        {
+            string path = Path.Join(TestUtils.FunctionDirectory, "testBasicFunction.ps1");
+            var functionInfo = TestUtils.NewAzFunctionInfo(path, string.Empty);
+
+            Assert.Empty(FunctionMetadata.OutputBindingCache);
+            FunctionMetadata.RegisterFunctionMetadata(_testManager.InstanceId, functionInfo);
+            Assert.Single(FunctionMetadata.OutputBindingCache);
+            FunctionMetadata.UnregisterFunctionMetadata(_testManager.InstanceId);
+            Assert.Empty(FunctionMetadata.OutputBindingCache);
+        }
+
         [Fact]
         public void ProfileShouldWork()
         {