slint-ui/slint · error · std::io::Error

path not found

Error message

path not found

What it means

In tools/lsp/preview.rs (around line 2201), an async closure used for loading external files checks a HashMap<PathBuf, String> of source code; if the requested PathBuf is absent it returns Some(Err(io::Error::NotFound, "path not found")) wrapped in a Result handed back to the caller. It indicates the preview's in-memory code map does not contain the requested file, so it cannot be served (with the fixed version tag Some(24) otherwise).

Solutions

  1. Populate the `code` map with all dependencies (full import closure) before triggering the load.
  2. Canonicalize paths (same separators, absolute) before inserting and looking up in the map.
  3. Handle the Err result by falling back to fetching the file through the normal file-system/URL path.

Example fix

// before
let Some(source) = code.get(&path) else {
    return Some(Result::Err(std::io::Error::new(
        std::io::ErrorKind::NotFound,
        "path not found",
    )));
};
// after
let canonical = path.canonicalize().unwrap_or_else(|_| path.clone());
let Some(source) = code.get(&canonical).or_else(|| code.get(&path)) else {
    return Some(Result::Err(std::io::Error::new(
        std::io::ErrorKind::NotFound,
        format!("path not found: {}", path.display()),
    )));
};
Defensive patterns

Strategy: try-catch

Validate before calling

// before invoking the async loader
if (!codeMap.has(pathKey)) {
  console.warn("loader: no source for", pathKey, "— registering first");
  codeMap.set(pathKey, loadFromDisk(pathKey));
}

Try / catch

match loader(path).await {
    Ok((version, source)) => compile_with(version, source),
    Err(e) if e.kind() == std::io::ErrorKind::NotFound => compile_from_disk_fallback(path),
    Err(e) => report(e),
}

Prevention

When it happens

Trigger: The loader callback is invoked for a path that was never inserted into the `code` map captured by the closure — e.g. a dependency file requested before the preview populated its map, or a path with different casing/canonicalization than the keys stored.

Common situations: Live-Preview serving imported dependencies in WASM/browser context where only the main document was compiled into the map; or a path separator mismatch (Windows backslash vs URL slash) making the lookup key differ.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of slint-ui/slint@3a7e700487 (2026-09-16). Data as JSON: /api/errors/6034bb0b61edaa58. Report an issue: GitHub.

Appendix: source

Thrown at tools/lsp/preview.rs:2208

    ) -> ComponentInstance {
        let code = Rc::new(code);

        let path = main_test_file_name();
        let source_code = code.get(&path).unwrap().clone();
        let (diagnostics, component_definition, _, _) = spin_on::spin_on(super::parse_source(
            Default::default(),
            path,
            Some(24),
            source_code.to_string(),
            style.to_string(),
            None,
            move |path| {
                let code = code.clone();
                let path = PathBuf::from(&path);

                Box::pin(async move {
                    let Some(source) = code.get(&path) else {
                        return Some(Result::Err(std::io::Error::new(
                            std::io::ErrorKind::NotFound,
                            "path not found",
                        )));
                    };
                    Some(Ok((Some(24), source.clone())))
                })
            },
        ));

        assert!(diagnostics.is_empty());

        component_definition.unwrap().create().unwrap()
    }

    #[track_caller]
    pub fn interpret_test(style: &str, source_code: &str) -> ComponentInstance {
        let code = HashMap::from([(main_test_file_name(), source_code.to_string())]);
        interpret_test_with_sources(style, code)

View on GitHub (pinned to 3a7e700487)