rust-lang/cargo · error

manifest path is absolute

Error message

manifest path is absolute

What it means

`write_manifest_upgrades` calls `manifest_path.parent().expect("manifest path is absolute")`. `Path::parent()` returns `None` only when the path has no parent component (e.g. `/`, `C:\`, or an empty path) — not for ordinary absolute paths. The message is misleading: the real precondition is that the manifest path is not a filesystem root.

Source

Thrown at src/ops/cargo_update.rs:472

    }

    let mut any_file_has_changed = false;

    let items = std::iter::once((ws.root_manifest(), ws.unstable_features()))
        .chain(ws.members().map(|member| {
            (
                member.manifest_path(),
                member.manifest().unstable_features(),
            )
        }))
        .collect::<Vec<_>>();

    for (manifest_path, unstable_features) in items {
        trace!("updating TOML manifest at `{manifest_path:?}` with upgraded dependencies");

        let crate_root = manifest_path
            .parent()
            .expect("manifest path is absolute")
            .to_owned();

        let mut local_manifest = LocalManifest::try_new(&manifest_path)?;
        let mut manifest_has_changed = false;

        for dep_table in local_manifest.get_dependency_tables_mut() {
            for (mut dep_key, dep_item) in dep_table.iter_mut() {
                let dep_key_str = dep_key.get();
                let dependency = crate::workspace::editor::dependency::Dependency::from_toml(
                    ws.gctx(),
                    ws.root(),
                    &manifest_path,
                    unstable_features,
                    dep_key_str,
                    dep_item,
                )?;
                let name = &dependency.name;

View on GitHub (pinned to 0e07a15537)

Solutions

1. Report a cargo bug if `cargo update` triggers it; include the workspace layout and any `[workspace]` member glob patterns.
2. Check for unusual member paths (`path = "/"` or a member glob resolving to a root) in `Cargo.toml`.
3. If patching cargo, replace the `expect` with a `bail!` describing the offending path.

Example fix

// before
let crate_root = manifest_path.parent().expect("manifest path is absolute").to_owned();

// after
let crate_root = manifest_path.parent()
    .ok_or_else(|| anyhow::format_err!(
        "manifest path `{}` has no parent directory", manifest_path.display()))?
    .to_owned();

// Ensure every workspace manifest path has a parent before upgrade writing.
for (mp, _) in &items {
    if mp.parent().is_none() {
        return Err(anyhow!("manifest path `{}` has no parent dir", mp.display()));
    }
}

When it happens

Trigger: Fires if a workspace member's `manifest_path` is a root-level path with no parent — e.g. literally `/Cargo.toml` is not possible because `/Cargo.toml`'s parent is `/`, but a path equal to `/` or `` itself would. Realistically only via a malformed manifest path constructed programmatically or a virtual manifest sitting at the filesystem root.

Common situations: Extremely unlikely in practice; would require a manifest path that `parent()` cannot slice. Encountered in tests or tooling that passes a synthetic/empty path to the upgrade writer. End users running `cargo update` never hit this.

Related errors

• normalized have a path
• manifest validated
• returned early
• already a valid dependency
• local path

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/37c906adc0e694bc.json. Report an issue: GitHub.