cross-rs/cross · error

got of " " which is not a valid environment variable name…

Error message

got {var_type} of "{var}" which is not a valid environment variable name. the proper syntax is {var_syntax}

What it means

Generic validation guard in validate_env_var: a `-e VAR=value` / `--env` / `--set-env` style argument passed to the container engine was split on '=' and the name part (or the whole argument, when no '=' was present) contains characters outside [A-Za-z0-9_], so it cannot be a valid environment variable name. Fires at most once per invocation thanks to the `warned` flag, and is only emitted when no '=' was found, since names are still reported for key=value forms.

Solutions

1. Fix the argument to use only letters, digits and underscores in the variable name, e.g. `-e MY_VAR=value`
2. Include an `=` with a value if you meant to set a variable rather than pass one through from the host
3. Check for shell quoting problems that inject stray characters (spaces, dashes, newlines) into the env argument

When it happens

Trigger: Thrown at src/docker/shared.rs:896 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of cross-rs/cross@8c1a8aa4b6 (2026-09-13). Data as JSON: /api/errors/c2eb781985347091. Report an issue: GitHub.

Appendix: source

Thrown at src/docker/shared.rs:896

fn validate_env_var<'a>(
    var: &'a str,
    warned: &mut bool,
    var_type: &'static str,
    var_syntax: &'static str,
    msg_info: &mut MessageInfo,
) -> Result<(&'a str, Option<&'a str>)> {
    let (key, value) = match var.split_once('=') {
        Some((key, value)) => (key, Some(value)),
        _ => (var, None),
    };

    if value.is_none()
        && !*warned
        && !var
            .chars()
            .all(|c| matches!(c, 'a'..='z' | 'A'..='Z' | '_' | '0'..='9'))
    {
        msg_info.warn(format_args!(
            "got {var_type} of \"{var}\" which is not a valid environment variable name. the proper syntax is {var_syntax}"
        ))?;
        *warned = true;
    }

    if key == "CROSS_RUNNER" {
        eyre::bail!(
            "CROSS_RUNNER environment variable name is reserved and cannot be pass through"
        );
    }

    Ok((key, value))
}

impl CommandVariant {
    pub(crate) fn safe_command(&self) -> SafeCommand {
        SafeCommand::new(self.to_str())
    }

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