Add PSTypeName Support for Import-Csv and ConvertFrom-Csv (#5389)

closes #5134

Adds PSTypeName preservation on Import-Csv and ConvertFrom-Csv

src/Microsoft.PowerShell.Commands.Utility/commands/utility/CSVCommands.cs

@@ -1336,10 +1336,6 @@ namespace Microsoft.PowerShell.Commands
                     {
                         type = null;
                     }
-                    else
-                    {
-                        type = ImportExportCSVHelper.CSVTypePrefix + type;
-                    }
                 }
             }
             return type;
@@ -1606,11 +1602,6 @@ namespace Microsoft.PowerShell.Commands
             PSObject result = new PSObject();
             char delimiterlocal = delimiter;
             int unspecifiedNameIndex = 1;
-            if (type != null && type.Length > 0)
-            {
-                result.TypeNames.Clear();
-                result.TypeNames.Add(type);
-            }
             for (int i = 0; i <= names.Count - 1; i++)
             {
                 string name = names[i];
@@ -1638,6 +1629,13 @@ namespace Microsoft.PowerShell.Commands
                 _alreadyWarnedUnspecifiedName = true;
             }
 
+            if (type != null && type.Length > 0)
+            {
+                result.TypeNames.Clear();
+                result.TypeNames.Add(type);
+                result.TypeNames.Add(ImportExportCSVHelper.CSVTypePrefix + type);
+            }
+
             return result;
         }
     }

test/powershell/Modules/Microsoft.PowerShell.Utility/ConvertFrom-Csv.Tests.ps1

@@ -9,6 +9,11 @@ Describe "ConvertFrom-Csv" -Tags "CI" {
         $testColumns = @"
 a,b,c
 1,2,3
+"@
+        $testTypeData = @"
+#TYPE My.Custom.Object
+a,b,c
+1,2,3
 "@
     }
 
@@ -53,6 +58,13 @@ a,b,c
 
         $actualLength | Should Be 3
     }
+
+    It "Should Contain the Imported Type data" {
+        $actualData = $testTypeData | ConvertFrom-Csv
+        $actualData.PSObject.TypeNames.Count | Should Be 2
+        $actualData.PSObject.TypeNames[0] | Should Be "My.Custom.Object"
+        $actualData.PSObject.TypeNames[1] | Should Be "CSV:My.Custom.Object"
+    }
 }
 
 Describe "ConvertFrom-Csv DRT Unit Tests" -Tags "CI" {

test/powershell/Modules/Microsoft.PowerShell.Utility/Import-Csv.Tests.ps1

@@ -80,16 +80,17 @@ Describe "Import-Csv #Type Tests" -Tags "CI" {
         Remove-Item -Path $testfile -Force -ErrorAction SilentlyContinue
         $processlist = (Get-Process)[0..1]
         $processlist | Export-Csv -Path $testfile -Force -IncludeTypeInformation
-        # Import-Csv add "CSV:" before actual type
-        $expectedProcessType = "CSV:System.Diagnostics.Process"
+        $expectedProcessTypes = "System.Diagnostics.Process","CSV:System.Diagnostics.Process"
     }
 
     It "Test import-csv import Object" {
         $importObjectList = Import-Csv -Path $testfile
         $processlist.Count | Should Be $importObjectList.Count
 
-        $importType = $importObjectList[0].psobject.TypeNames[0]
-        $importType | Should Be $expectedProcessType
+        $importTypes = $importObjectList[0].psobject.TypeNames
+        $importTypes.Count | Should Be $expectedProcessTypes.Count
+        $importTypes[0] | Should Be $expectedProcessTypes[0]
+        $importTypes[1] | Should Be $expectedProcessTypes[1]
     }
 }