Trouble Creating Directory for Portable Database

[gzuuus]

Hello! I'm new to Tauri and I'm really enjoying it, but I have some questions regarding filesystem management. After reading through the discussions and documentation, I haven't been able to find a solution to my problem.

I am currently developing an application that utilizes a portable database, specifically SQLite. This database will store information about the various users who can use the application, meaning that each user will utilize a separate database, making it portable. However, I am encountering issues when attempting to create a directory to store these databases. When I build and test my application, it crashes.

In my main.rs file, I define the directory path as follows:

const ACCOUNT_PATH: &str = "./.accounts";

Then, within my main() function, I include the following code:

fn main() -> Result<()> {
    if !Path::new(ACCOUNT_PATH).exists() {
        fs::create_dir(ACCOUNT_PATH)
            .expect("Failed to create directory");
    }
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![
...
])
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
    Ok(())
}

Additionally, in my tauri.conf.json file, I have included the following configuration:

{
  "allowlist": {
    "all": true,
    "fs": {
      "all": true,
      "scope": ["**"]
    },
    "os": {
      "all": true
    },
    "path": {
      "all": true
    }
  }
}

The above setup functions correctly in my development environment; however, upon building my Linux .deb package, the application operates without any problems, whereas the .AppImage version crashes with the following error:

Failed to create directory: Os { code: 30, kind: ReadOnlyFilesystem, message: "Read-only file system" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Similarly, the macOS version encounters the same issue. Could someone please help me understand what I might be doing incorrectly? Thank you in advance!

[FabianLars]

I'm surprised the .deb works to be honest, it should be read-only too. Really the only bundle type that's reliably writable is the nsis installer on windows in perUser installmode. Just to be safe i assume that .deb is read-only below too.

So, if you plan to support .deb, .dmg, .msi, or setup.exe (nsis) in perMachine installmode you have to use a "well known" location to store the file instead of next to the app. For example the documents dir, or application specific data folders (f.e. https://tauri.app/v1/api/js/path#appdatadir).
There would be really no way around that.

If you only care about .appimage you could read the APPIMAGE or OWD environment variables (it was one of those 2) to get the path of the .appimage file. Currently you're using a path relative to the current working dir but the current working dir is a temporary read-only dir in /tmp.

On macOS, even though .app is just a simple directory i think macos makes it read-only once the app is running, i could be totally wrong about that. If the user moves that file into the /Applications dir (i think that's what users typically do?) it will be read-only though.

tldr, depending on the app's current working dir is super risky and rarely the right thing to do.

[gzuuus]

So, what is the way to proceed in order to create the directory correctly to save my databases? Should I do something like this in my tauri.conf.json?

"fs": {
  "all": true,
  "scope": ["$APPDATA/", "$APPDATA/**"]
}

And define my path variable as const ACCOUNT_PATH: &str = "$APPDATA/.accounts";? However, I have tried again to do the build, and I still get the same error on Linux.

Forgive my ignorance, but it would help me a lot if you could show me the best way to deal with this case, as this is my first project with Tauri and native applications.

Thanks in advance!

[FabianLars]

The scope setting is only relevant for the javascript/webview side so let's ignore that for now.

Tauri also does not change the behavior of std::fs (it couldn't do that anyway) so "$APPDATA/.accounts" means that it will try to create a $APPDATA (literally) directory in the current working dir.

To get the correct dir you'll have to use https://docs.rs/tauri/latest/tauri/struct.PathResolver.html#method.app_data_dir, for this you need access to an App/AppHandle which typically means to move the code into tauri's setup hook:

tauri::Builder::default()
  .setup(|app| {
    // This will give us the actual path to $APPDATA
    let path = app.path_resolver().app_data_dir().expect("This should never be None");
    // append a .accounts folder
    let path = path.join(".accounts/");
    
    // we can't expect either of those 2 folders to exist already so we use create_dir_all instead of create_dir.
    create_dir_all(&path);
    
    Ok(())
  })

If you can't move it into the setup hook you can use tauri::path::data_dir() and append the bundle identifier or your app name yourself.

[gzuuus]

It worked! wow, thank you very much for this! I was a bit confused about how to interact with my file system in tauri, whether to use it in the rust part, or in the js part, since there are both possibilities. My bundles are working as expected now :)