astral-sh/uv · error · anyhow::Error

Cannot use `{}` as an override file

Error message

Cannot use `{}` as an override file

What it means

Thrown in RequirementsSpecification::from_sources (crates/uv-requirements/src/specification.rs:440) when the overrides list contains a RequirementsSource::PylockToml variant. Overrides are requirements.txt-format pins applied to the resolution; a full lock file is neither parsed nor applied that way, so uv rejects the combination at assembly time (mirrors error 43 at the API level).

Source

Thrown at crates/uv-requirements/src/specification.rs:440

            } else {
                None
            }
        }) {
            return Err(anyhow::anyhow!(
                "Cannot use `{}` as a constraint file",
                pylock_toml.user_display()
            ));
        }

        // Disallow `pylock.toml` files as overrides.
        if let Some(pylock_toml) = overrides.iter().find_map(|source| {
            if let RequirementsSource::PylockToml(path) = source {
                Some(path)
            } else {
                None
            }
        }) {
            return Err(anyhow::anyhow!(
                "Cannot use `{}` as an override file",
                pylock_toml.user_display()
            ));
        }

        // Disallow `pylock.toml` files as excludes.
        if let Some(pylock_toml) = excludes.iter().find_map(|source| {
            if let RequirementsSource::PylockToml(path) = source {
                Some(path)
            } else {
                None
            }
        }) {
            return Err(anyhow::anyhow!(
                "Cannot use `{}` as an exclude file",
                pylock_toml.user_display()
            ));
        }

View on GitHub (pinned to f1a42680ff)

Solutions

1. Drop the pylock.toml from the overrides list and supply overrides.txt-style pins instead
2. Export the pins: `uv export --format requirements-txt -o overrides.txt`
3. Reconsider the design — to install exactly the lock, use it as the requirements source, not an override

Example fix

# before (programmatic)
overrides: vec![RequirementsSource::PylockToml(lock.into())],
// after
overrides: vec![RequirementsSource::RequirementsTxt(ovr.into())],

let bad = overrides.iter().any(|s| matches!(s, RequirementsSource::PylockToml(_)));
if bad {
    return Err(anyhow::anyhow!("refusing to assemble spec: pylock.toml is not an override source"));
}

fn is_pylock_source(s: &RequirementsSource) -> bool {
    matches!(s, RequirementsSource::PylockToml(_))
}

match RequirementsSpecification::from_sources(/* .. */).await {
    Err(err) if err.to_string().contains("as an override file") => {
        // replace with an exported overrides.txt and reassemble
    }
    spec => spec?,
}

When it happens

Trigger: Programmatic from_sources call with a PylockToml source inside the overrides Vec; an upstream flow that classified an --overrides path as a pylock source before reaching this constructor; only the first match is reported.

Common situations: Automation layering a corporate lock file as overrides on user requirements; wrapper tools assembling source lists from globs.

Related errors

• Cannot specify overrides with a `pylock.toml` file
• The file `{}` appears to be a `pylock.toml` file, but overri
• Cannot use `{}` as a constraint file
• Cannot use `{}` as an exclude file
• Cannot specify additional requirements alongside a `pylock.t

AI-assisted analysis of astral-sh/uv@f1a42680ff (2026-08-16). Data as JSON: /api/errors/629d425bf7b3699e. Report an issue: GitHub.