Change Get-FileHash to close file handles before writing output (#12474)

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

@@ -126,49 +126,10 @@ namespace Microsoft.PowerShell.Commands
 
             foreach (string path in pathsToProcess)
             {
-                byte[] bytehash = null;
-                string hash = null;
-                Stream openfilestream = null;
-
-                try
+                if (ComputeFileHash(path, out string hash))
                 {
-                    openfilestream = File.OpenRead(path);
-                    bytehash = hasher.ComputeHash(openfilestream);
-
-                    hash = BitConverter.ToString(bytehash).Replace("-", string.Empty);
                     WriteHashResult(Algorithm, hash, path);
                 }
-                catch (FileNotFoundException ex)
-                {
-                    var errorRecord = new ErrorRecord(
-                        ex,
-                        "FileNotFound",
-                        ErrorCategory.ObjectNotFound,
-                        path);
-                    WriteError(errorRecord);
-                }
-                catch (UnauthorizedAccessException ex)
-                {
-                    var errorRecord = new ErrorRecord(
-                        ex,
-                        "UnauthorizedAccessError",
-                        ErrorCategory.InvalidData,
-                        path);
-                    WriteError(errorRecord);
-                }
-                catch (IOException ioException)
-                {
-                    var errorRecord = new ErrorRecord(
-                        ioException,
-                        "FileReadError",
-                        ErrorCategory.ReadError,
-                        path);
-                    WriteError(errorRecord);
-                }
-                finally
-                {
-                    openfilestream?.Dispose();
-                }
             }
         }
 
@@ -190,6 +151,61 @@ namespace Microsoft.PowerShell.Commands
             }
         }
 
+        /// <summary>
+        /// Read the file and calculate the hash.
+        /// </summary>
+        /// <param name="path">Path to file which will be hashed.</param>
+        /// <param name="hash">Will contain the hash of the file content.</param>
+        /// <returns>Boolean value indicating whether the hash calculation succeeded or failed.</returns>
+        private bool ComputeFileHash(string path, out string hash)
+        {
+            byte[] bytehash = null;
+            Stream openfilestream = null;
+
+            hash = null;
+
+            try
+            {
+                openfilestream = File.OpenRead(path);
+
+                bytehash = hasher.ComputeHash(openfilestream);
+                hash = BitConverter.ToString(bytehash).Replace("-", string.Empty);
+            }
+            catch (FileNotFoundException ex)
+            {
+                var errorRecord = new ErrorRecord(
+                    ex,
+                    "FileNotFound",
+                    ErrorCategory.ObjectNotFound,
+                    path);
+                WriteError(errorRecord);
+            }
+            catch (UnauthorizedAccessException ex)
+            {
+                var errorRecord = new ErrorRecord(
+                    ex,
+                    "UnauthorizedAccessError",
+                    ErrorCategory.InvalidData,
+                    path);
+                WriteError(errorRecord);
+            }
+            catch (IOException ioException)
+            {
+                var errorRecord = new ErrorRecord(
+                    ioException,
+                    "FileReadError",
+                    ErrorCategory.ReadError,
+                    path);
+                WriteError(errorRecord);
+            }
+            finally
+            {
+                openfilestream?.Dispose();
+            }
+
+            return hash != null;
+        }
+
         /// <summary>
         /// Create FileHashInfo object and output it.
         /// </summary>

test/powershell/Modules/Microsoft.PowerShell.Utility/Get-FileHash.Tests.ps1

@@ -77,4 +77,19 @@ Describe "Get-FileHash" -Tags "CI" {
             $result.Path | Should -Be $testDocument
         }
     }
+
+    Context "File should be closed before Get-FileHash writes pipeline output" {
+        It "Should be able to edit the file without 'file is in use' exceptions" {
+            # This test runs against a copy of the document
+            # because it involves renaming it,
+            # and that might break tests added later on.
+            $testDocumentCopy = "${testDocument}-copy"
+            Copy-Item -Path $testdocument -Destination $testDocumentCopy
+
+            $newPath = Get-FileHash -Path $testDocumentCopy | Rename-Item -NewName {$_.Hash} -PassThru
+            $newPath.FullName | Should -Exist
+
+            Remove-Item -Path $testDocumentCopy -Force
+        }
+    }
 }