PowerShell · daxian-dbw · Feb 17, 2017 · Feb 13, 2017 · Feb 15, 2017 · Feb 16, 2017
diff --git a/src/System.Management.Automation/engine/InitialSessionState.cs b/src/System.Management.Automation/engine/InitialSessionState.cs
@@ -1309,7 +1309,7 @@ public void Add(T item)
         }
 
         /// <summary>
-        ///
+        /// Add items to this collection.
         /// </summary>
         /// <param name="items"></param>
         public void Add(IEnumerable<T> items)
@@ -1326,6 +1326,27 @@ public void Add(IEnumerable<T> items)
             }
         }
 
+        /// <summary>
+        /// Special add for TypeTable type entries that removes redundant file entries.
+        /// </summary>
+        internal void AddTypeTableTypesInfo(IEnumerable<T> items)
+        {
+            if (typeof(T) != typeof(SessionStateTypeEntry)) { throw new PSInvalidOperationException(); }
+
+            lock (_syncObject)
+            {
+                foreach (var element in items)
+                {
+                    var typeEntry = element as SessionStateTypeEntry;
+                    if (typeEntry.TypeData != null)
+                    {
+                        // Skip type file entries.
+                        _internalCollection.Add(element);
+                    }
+                }
+            }
+        }
+
         /// <summary>
         /// Get enumerator for this collection.
         /// </summary>
@@ -3851,7 +3872,12 @@ internal void UpdateTypes(ExecutionContext context, bool updateOnly)
                     context.TypeTable = typeTable;
 
                     Types.Clear();
-                    Types.Add(typeTable.typesInfo);
+
+                    // A TypeTable contains types info along with type file references used to create the types info,
+                    // which is redundant information.  When resused in a runspace the ISS unpacks the file types again
+                    // resulting in duplicate types and duplication errors when processed.
+                    // So use this special Add method to filter all types files found in the TypeTable.
+                    Types.AddTypeTableTypesInfo(typeTable.typesInfo);
 
                     return;
                 }

diff --git a/test/powershell/Common/TestTypeFile.ps1xml b/test/powershell/Common/TestTypeFile.ps1xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8" ?>
+
+<Types>
+  <Type>
+    <Name>System.Array</Name>
+    <Members>
+      <AliasProperty>
+        <Name>Counts</Name>
+        <ReferencedMemberName>Length</ReferencedMemberName>
+      </AliasProperty>
+    </Members>
+  </Type>
+</Types>
diff --git a/test/powershell/engine/InitialSessionState.Tests.ps1 b/test/powershell/engine/InitialSessionState.Tests.ps1
@@ -54,4 +54,75 @@ Describe "InitialSessionState capacity" -Tags CI {
         $ps.AddScript('New-Alias -Name a5000 -Value f1; a5000').Invoke() | Should Be "fn f1"
         $ps.Streams.Error | Should Be $null
     }
-}
+}
+
+##
+## A reused InitialSessionState created from a TypeTable should not have duplicate types.
+##
+Describe "TypeTable duplicate types in reused runspace InitialSessionState TypeTable" -Tags 'Feature' {
+
+    Context "No duplicate types test" {
+
+        BeforeAll {
+
+            $typeTable = [System.Management.Automation.Runspaces.TypeTable]::new([string[]](Join-Path $PSScriptRoot "../Common/TestTypeFile.ps1xml"))
+            [initialsessionstate] $iss = [initialsessionstate]::Create()
+            $iss.Types.Add($typeTable)
+            [runspace] $rs1 = [runspacefactory]::CreateRunspace($iss)
+
+            # Process TypeTable types from ISS
+            $rs1.Open()
+
+            # Get processed ISS from runspace.
+            $issReused = $rs1.InitialSessionState.Clone()
+            $issReused.ThrowOnRunspaceOpenError = $true
+
+            # Create new runspace with reused ISS.
+            $rs2 = [runspacefactory]::CreateRunspace($issReused)
+        }
+
+        AfterAll {
+
+            if ($rs1 -ne $null) { $rs1.Dispose() }
+            if ($rs2 -ne $null) { $rs2.Dispose() }
+        }
+
+        It "Verifies that a reused InitialSessionState object created from a TypeTable object does not have duplicate types" {
+
+            { $rs2.Open() } | Should Not Throw
+        }
+    }
+
+    Context "Cannot use shared TypeTable in ISS test" {
+
+        BeforeAll {
+
+            # Create default ISS and add shared TypeTable.
+            $typeTable = [System.Management.Automation.Runspaces.TypeTable]::new([string[]](Join-Path $PSScriptRoot "../Common/TestTypeFile.ps1xml"))
+            [initialsessionstate] $iss = [initialsessionstate]::CreateDefault2()
+            $iss.Types.Add($typeTable)
+            $iss.ThrowOnRunspaceOpenError = $true
+            [runspace] $rs = [runspacefactory]::CreateRunspace($iss)
+        }
+
+        AfterAll {
+
+            if ($rs -ne $null) { $rs.Dispose() }
+        }
+
+        It "Verifies that shared TypeTable is not allowed in ISS" {
+
+            # Process TypeTable types from ISS.
+            $errorId = ""
+            try
+            {
+                $rs.Open()
+                throw "No Exception!"
+            }
+            catch
+            {
+                $_.Exception.InnerException.ErrorRecord.FullyQualifiedErrorId | Should Be "ErrorsUpdatingTypes"
+            }
+        }
+    }
+}