FileStorageKey (Default) Creates Empty File Instead of Populating It with Data

[zachgibson]

Description

When using FileStorageKey<String>.Default, I’m seeing an issue where the file is created on disk with no contents, even though a default value is provided and used in memory. If I update that state the file then gets populated correctly.

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

FileStorageKey<T>.Default with a non-nil default value creates a file on disk with the contents of default value.

Actual behavior

FileStorageKey<T>.Default with a non-nil default value creates an empty file on disk.

Reproducing project

FileStorageRepro.zip

Sharing version information

2.5.2

Destination operating system

macOS 15.3.1

Xcode version information

16.2

Swift Compiler version information

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0

[mbrandonw]

Hi @zachgibson, this is currently by design. We do not eagerly write the initial value to the external system (in any strategy, including appStorage). The reason a file with empty bytes is being written is because we need a file on disk to observe changes to it via dispatch source.

Can you describe what problem this is causing for you so that we can evaluate?

But since this isn't an issue with the library I am going to convert it to a discussion. Let's continue the conversation over there!