Fix file locking in attachments (#1377)

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+
+- Fix file locking in attachments ([#1377](https://github.com/getsentry/sentry-dotnet/pull/1377))
+
 ## 3.12.1
 
 ### Features

src/Sentry/FileAttachmentContent.cs

@@ -15,6 +15,12 @@ public class FileAttachmentContent : IAttachmentContent
         public FileAttachmentContent(string filePath) => _filePath = filePath;
 
         /// <inheritdoc />
-        public Stream GetStream() => File.OpenRead(_filePath);
+        public Stream GetStream() => new FileStream(
+            _filePath,
+            FileMode.Open,
+            FileAccess.Read,
+            FileShare.ReadWrite,
+            bufferSize: 4096,
+            useAsync: true);
     }
 }

test/Sentry.Tests/AttachmentTests.cs

@@ -0,0 +1,42 @@
+using Sentry.Testing;
+
+namespace Sentry.Tests;
+
+public class FileAttachmentContentTests
+{
+    [Fact]
+    public void DoesNotLock()
+    {
+        // Arrange
+        using var tempDir = new TempDirectory();
+        var filePath = Path.Combine(tempDir.Path, "MyFile.txt");
+        File.WriteAllText(filePath, "Hello world!");
+
+        var attachment = new FileAttachmentContent(filePath);
+        // Act
+        using (var stream = attachment.GetStream())
+        {
+            Assert.False(IsFileLocked(filePath));
+        }
+    }
+
+    private static bool IsFileLocked(string file)
+    {
+        try
+        {
+            using FileStream stream = new(file, FileMode.Open, FileAccess.ReadWrite);
+            stream.Close();
+        }
+        catch (IOException)
+        {
+            //the file is unavailable because it is:
+            //still being written to
+            //or being processed by another thread
+            //or does not exist (has already been processed)
+            return true;
+        }
+
+        //file is not locked
+        return false;
+    }
+}