invalid Nix package attribute

Error message

invalid Nix package attribute '{attribute}'; use a dotted attribute path (e.g. ripgrep or python3Packages.pip), or '<flake>#<attribute>'; pin versions in the flake reference, not with @version

What it means

The part after `#` (or the whole name when no `#` is present) must be a valid Nix attribute path: non-empty dot-separated parts of ASCII alphanumerics, `_`, `-`, or `'`. This error fires for anything else — empty attributes, `^out` output selectors, `@version` suffixes, `..`, or special characters — because mise delegates versioning and output selection to the flake, not the package string.

Solutions

Use a plain dotted attribute path: `ripgrep` or `python3Packages.pip`.
Pin a version by pinning the flake source revision (e.g. `github:owner/repo/<rev>#pkg`), not with `@version`.
Remove output selectors (`^out`) and Nix expression syntax from the attribute; select outputs in your own flake if needed.
Check the exact attribute name in `nix search nixpkgs <pkg>` or the flake's `packages.<system>` output.

Example fix

# before
packages = ["ripgrep@14.1.0"]

# after
packages = ["github:NixOS/nixpkgs/nixos-24.05#ripgrep"]

Defensive patterns

Strategy: validation

Validate before calling

fn valid_attribute(attr: &str) -> bool {
    attr.split('.').all(|p| !p.is_empty()
        && p.chars().all(|c| c.is_ascii_alphanumeric() || matches!(c, '_' | '-' | '\'')))
}

Prevention

Never use pkg@version syntax with Nix packages
Pin versions via flake URL revisions instead
Verify attribute names with `nix search nixpkgs <pkg>`
Avoid ^output selectors and Nix expressions in package strings

When it happens

Trigger: `Installable::parse` receives names like `hello@1.2`, `hello^out`, `hello..world`, `#` with an empty attribute, or attributes containing `/`, `$`, `${...}`, etc. Called from install, upgrade, and matching_entries.

Common situations: Users porting apt/npm habits and writing `pkg@version` (mise explicitly tells you to pin via the flake source revision instead); attempting Nix output selection (`^out`) or nixpkgs expressions inside the attribute; typos with double dots.

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/23b8c4ffc55c8418. Report an issue: GitHub.

Appendix: source

Thrown at src/system/packages/nix.rs:47

            Some((source, attribute)) => {
                if source.is_empty()
                    || source.starts_with('-')
                    || source.starts_with('.')
                    || source.starts_with('/')
                    || source
                        .strip_prefix("path:")
                        .is_some_and(|p| !p.starts_with('/'))
                {
                    bail!(
                        "invalid Nix flake reference '{source}'; use a registry name, URL, or path:/absolute/path"
                    );
                }
                (source, attribute, true)
            }
            None => ("nixpkgs", name, false),
        };
        if !valid_attribute(attribute) {
            bail!(
                "invalid Nix package attribute '{attribute}'; use a dotted attribute path (e.g. ripgrep or python3Packages.pip), or '<flake>#<attribute>'; pin versions in the flake reference, not with @version"
            );
        }
        Ok(Self {
            source,
            attribute,
            explicit,
        })
    }

    fn argument(&self) -> String {
        format!("{}#{}", self.source, self.attribute)
    }
}

fn valid_attribute(attribute: &str) -> bool {
    attribute.split('.').all(|part| {
        !part.is_empty()

View on GitHub (pinned to 533346cc37)