From be99f03bacd3ebe452733dbfaf61837dd3326b66 Mon Sep 17 00:00:00 2001
From: Carl Johnsen <carl-johannes@di.ku.dk>
Date: Sun, 5 Jan 2025 10:41:33 +0100
Subject: [PATCH] VerifyLocalBlocks wasn't respecting dry run properly

---
 .../Main/Operation/Restore/FileProcessor.cs   | 20 +++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/Duplicati/Library/Main/Operation/Restore/FileProcessor.cs b/Duplicati/Library/Main/Operation/Restore/FileProcessor.cs
index 801f6e7b7..83fa6c115 100644
--- a/Duplicati/Library/Main/Operation/Restore/FileProcessor.cs
+++ b/Duplicati/Library/Main/Operation/Restore/FileProcessor.cs
@@ -462,7 +462,11 @@ namespace Duplicati.Library.Main.Operation.Restore
 
                 // Open both files, as the target file is still being read to produce the overall file hash, if all the blocks are present across both the target and original files.
                 using var f_original = SystemIO.IO_OS.FileOpenRead(file.OriginalPath);
-                using var f_target = SystemIO.IO_OS.FileOpenWrite(file.TargetPath);
+                using var f_target = options.Dryrun ?
+                    (SystemIO.IO_OS.FileExists(file.TargetPath) ?
+                        SystemIO.IO_OS.FileOpenRead(file.TargetPath) :
+                        null) :
+                    SystemIO.IO_OS.FileOpenWrite(file.TargetPath);
                 var buffer = new byte[options.Blocksize];
                 long bytes_read = 0;
                 long bytes_written = 0;
@@ -496,6 +500,8 @@ namespace Duplicati.Library.Main.Operation.Restore
                                 missing_blocks.Add(blocks[j]);
                             }
                             else
+                            {
+                                if (!options.Dryrun)
                             {
                                 try
                                 {
@@ -509,6 +515,7 @@ namespace Duplicati.Library.Main.Operation.Restore
                                         results.BrokenLocalFiles.Add(file.TargetPath);
                                     }
                                     throw;
+                                    }
                                 }
                                 bytes_read += read;
                                 bytes_written += read;
@@ -533,8 +540,8 @@ namespace Duplicati.Library.Main.Operation.Restore
                         // The current block is not a missing block - read from the target file.
                         try
                         {
-                            f_target.Seek(i * options.Blocksize, SeekOrigin.Begin);
-                            read = await f_target.ReadAsync(buffer, 0, options.Blocksize);
+                            f_target?.Seek(i * options.Blocksize, SeekOrigin.Begin);
+                            read = await f_target?.ReadAsync(buffer, 0, options.Blocksize);
                         }
                         catch (Exception)
                         {
@@ -555,7 +562,7 @@ namespace Duplicati.Library.Main.Operation.Restore
                     if (Convert.ToBase64String(filehasher.Hash) == file.Hash)
                     {
                         // Truncate the file if it is larger than the expected size.
-                        if (file.Length < f_target.Length)
+                        if (file.Length < f_target?.Length)
                         {
                             if (options.Dryrun)
                             {
@@ -588,6 +595,11 @@ namespace Duplicati.Library.Main.Operation.Restore
                     }
                 }
 
+                if (options.Dryrun)
+                {
+                    Logging.Log.WriteDryrunMessage(LOGTAG, "DryrunRestore", @$"Would have restored {verified_blocks.Count} blocks ({bytes_written} bytes) from ""{file.OriginalPath}"" to ""{file.TargetPath}""");
+                }
+
                 return (bytes_written, missing_blocks);
             }
             else