rust-lang/cargo · error

` ` resolved to non-UTF value (` `)

Error message

`{}` resolved to non-UTF value (`{}`)

What it means

In the same `resolve_relative_path` function, when `diff_paths` succeeds the resulting `PathBuf` is converted to a string via `to_str()`. If the path contains non-UTF-8 bytes (valid on Unix for arbitrary OS paths), `to_str()` returns `None` and the function errors, interpolating the label and the lossy display of the path. This guards downstream string handling from non-UTF-8 paths.

Solutions

1. Rename the offending path component(s) to valid UTF-8 so `to_str()` succeeds.
2. Set the `LANG`/`LC_ALL` locale appropriately and ensure the filesystem path is UTF-8 encoded.
3. Move the workspace to a directory tree whose every component is valid UTF-8.

Example fix

# before: a non-UTF-8 directory name (e.g. raw bytes)
mv $'bad\xffdir' gooddir
# then re-run cargo — resolve_relative_path will succeed

use std::path::Path;
fn all_components_utf8(p: &Path) -> bool {
    p.components().all(|c| c.as_os_str().is_char_boundary(0) && c.as_os_str().to_str().is_some())
}
// verify every workspace path component is UTF-8 before path relativization
assert!(all_components_utf8(Path::new("/Users/me/ws")));

When it happens

Trigger: Calling `resolve_relative_path` where the relativized result contains invalid UTF-8 bytes — typically on Unix when a workspace path component uses non-UTF-8 bytes (e.g. a directory named with Latin-1 or raw bytes), and `diff_paths` produces a relative path preserving those bytes.

Common situations: Workspaces created by tooling that preserves byte-accurate names, files copied from systems with different encodings, or deliberately non-UTF-8 paths used in test fixtures. The error surfaces the moment Cargo tries to treat the path as a string for lockfile/manifest relativization.

Related errors

• non UTF8 path
• can only edit absolute paths, got
• Character at line is invalid. Cargo only supports UTF-8.
• {}: {:?}
• no executable for ` ` found in PATH

AI-assisted analysis of rust-lang/cargo@98a09e7e7d (2026-08-11). Data as JSON: /api/errors/07df17af2ee9358f. Report an issue: GitHub.

Appendix: source

Thrown at src/workspace/workspace.rs:2096

pub fn resolve_relative_path(
    label: &str,
    old_root: &Path,
    new_root: &Path,
    rel_path: &str,
) -> CargoResult<String> {
    let joined_path = normalize_path(&old_root.join(rel_path));
    match diff_paths(joined_path, new_root) {
        None => Err(anyhow!(
            "`{}` was defined in {} but could not be resolved with {}",
            label,
            old_root.display(),
            new_root.display()
        )),
        Some(path) => Ok(path
            .to_str()
            .ok_or_else(|| {
                anyhow!(
                    "`{}` resolved to non-UTF value (`{}`)",
                    label,
                    path.display()
                )
            })?
            .to_owned()),
    }
}

/// Finds the path of the root of the workspace.
pub fn find_workspace_root(
    manifest_path: &Path,
    gctx: &GlobalContext,
) -> CargoResult<Option<PathBuf>> {
    find_workspace_root_with_loader(manifest_path, gctx, |self_path| {
        let source_id = SourceId::for_manifest_path(self_path)?;
        let manifest = read_manifest(self_path, source_id, gctx)?;
        Ok(manifest

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