slint-ui/slint · warning

Failed to create a Slint file in

Error message

Failed to create a Slint file in {}: {error}

What it means

The editor preview's file-tree 'create new Slint file' action failed. The plugin resolved a create-controller for the project root and asked it to create a new .slint file; the underlying create operation returned an Err, which is logged as a warning with the project root path. The UI does not surface a hard error - it degrades to a logged warning.

Solutions

1. Check the logged error detail and verify the directory controller.root.display() exists and is writable
2. Ensure the intended file name is valid and does not already exist
3. Rebuild/refresh the project controller so it points at the actual project root
4. Create the file manually in the IDE and reload the preview

Example fix

// before
return Default::default();
// after
// surface the failure instead of swallowing it
match controller.create_new_slint_file(&project) {
    Ok(path) => /* update tree with path */,
    Err(error) => show_error_notification(&format!("Failed to create file: {error}")),
}

if (!controller.root.as_path().is_dir()) { eprintln!("project root missing: {}", controller.root.display()); return; }
if std::fs::metadata(&controller.root).map(|m| m.permissions().readonly()).unwrap_or(true) { eprintln!("project root read-only"); return; }

fn is_writable_dir(p: &std::path::Path) -> bool {
    std::fs::metadata(p).map(|m| m.is_dir() && !m.permissions().readonly()).unwrap_or(false)
}

match controller.create_new_slint_file(&project) {
    Ok(path) => refresh_tree(&path),
    Err(e) => notify_user(&format!("Create failed: {e}")),
}

When it happens

Trigger: Calling the create-new-file handler when controller.create_new_slint_file(&project) fails, e.g. the target directory is not writable, the file already exists, or the project path is invalid.

Common situations: User tries to create a new .slint file from the IDE preview's file tree in a read-only directory, a path with invalid characters, or when the project root moved/deleted after the controller was built.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• a setter belongs to a field
• an identifier
• attempt to multiply with overflow
• binding was of the wrong type
• Called a not-implemented method

AI-assisted analysis of slint-ui/slint@3a7e700487 (2026-09-16). Data as JSON: /api/errors/16a4f8e849d7e02b. Report an issue: GitHub.

Appendix: source

Thrown at tools/editor/preview/ui/file_tree.rs:44

    project: &Project<'_>,
    project_weak: slint::Weak<Project<'static>>,
) -> SharedFileTreeController {
    project.set_file_tree(Default::default());
    project.set_selected_project_file(Default::default());

    let controller: SharedFileTreeController = Rc::new(RefCell::new(None));

    let controller_for_create = controller.clone();
    let project_weak_for_create = project_weak.clone();
    project.on_create_new_slint_file(move || {
        let Some(project) = project_weak_for_create.upgrade() else {
            return Default::default();
        };
        let mut controller = controller_for_create.borrow_mut();
        let Some(controller) = controller.as_mut() else {
            return Default::default();
        };
        controller.create_new_slint_file(&project).err().map_or_else(
            SharedString::default,
            |error| {
                tracing::warn!(
                    "Failed to create a Slint file in {}: {error}",
                    controller.root.display()
                );
                error.to_shared_string()
            },
        )
    });

    let controller_for_select = controller.clone();
    let api_weak_for_select = api_weak.clone();
    let project_weak_for_select = project_weak.clone();
    api.on_file_tree_select(move |path| {
        if let Some(api) = api_weak_for_select.upgrade()
            && let Some(project) = project_weak_for_select.upgrade()
            && let Some(controller) = controller_for_select.borrow_mut().as_mut()

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