rust-lang/cargo · error

"--package <SPEC>" requires a SPEC format value. Run `cargo

Error message

"--package <SPEC>" requires a SPEC format value.
Run `cargo help pkgid` for more information about SPEC format.

What it means

In `cargo uninstall` (uninstall.rs:37-43), `is_present_with_zero_values("package")` is true when the user passes `--package` (or `-p`) with no value. Because `--package <SPEC>` requires a SPEC, Cargo bails and points to `cargo help pkgid` for the accepted spec grammar.

Source

Thrown at src/bin/cargo/commands/uninstall.rs:38

        .arg_silent_suggestion()
        .arg_package_spec_simple(
            "Package to uninstall",
            ArgValueCandidates::new(get_installed_package_candidates),
        )
        .arg(
            multi_opt("bin", "NAME", "Only uninstall the binary NAME")
                .help_heading(heading::TARGET_SELECTION),
        )
        .after_help(color_print::cstr!(
            "Run `<bright-cyan,bold>cargo help uninstall</>` for more detailed information.\n"
        ))
}

pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
    let root = args.get_one::<String>("root").map(String::as_str);

    if args.is_present_with_zero_values("package") {
        return Err(anyhow::anyhow!(
            "\"--package <SPEC>\" requires a SPEC format value.\n\
            Run `cargo help pkgid` for more information about SPEC format."
        )
        .into());
    }

    let specs = args
        .get_many::<String>("spec")
        .unwrap_or_else(|| args.get_many::<String>("package").unwrap_or_default())
        .map(String::as_str)
        .collect();
    ops::uninstall(root, specs, &values(args, "bin"), gctx)?;
    Ok(())
}

fn get_installed_crates() -> Vec<clap_complete::CompletionCandidate> {
    get_installed_crates_().unwrap_or_default()
}

View on GitHub (pinned to 0e07a15537)

Solutions

1. Provide a SPEC value: `cargo uninstall -p my-crate`.
2. Use a full spec if needed: `cargo uninstall -p my-crate@1.2.3` (see `cargo help pkgid`).
3. Drop `-p` entirely to uninstall by positional name: `cargo uninstall my-crate`.

Example fix

// before
$ cargo uninstall -p
error: "--package <SPEC>" requires a SPEC format value.

// after
$ cargo uninstall -p my-crate

if package_flag_present && package_value.is_none() {
    return Err("--package requires a SPEC; see `cargo help pkgid`");
}

fn has_package_spec(p: Option<&str>) -> bool {
    p.map(|s| !s.trim().is_empty()).unwrap_or(false)
}

When it happens

Trigger: Running `cargo uninstall --package` with no argument, or `cargo uninstall -p` followed by nothing.

Common situations: Shell quoting bug that swallowed the package name; copy-pasting a command missing the trailing spec; expecting `-p` to act as a flag rather than an option.

Related errors

• {}
• cannot specify both `@{v}` and `--version`
• missing crate name for `@{v}`
• argument for --color must be auto, always, or never, but fou
• subcommand is required, add a subcommand to the command alia

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/8e8d59a3c24b9bb9.json. Report an issue: GitHub.