jdx/mise · error

aqua var `{}` must be a string, got {}

Error message

aqua var `{}` must be a string, got {}

What it means

Aqua packages can define template variables (`vars`) used in registry expressions. toml_string_var enforces that each aqua var used by the embedded plugin is a TOML string. If a var is defined with a non-string TOML type (integer, boolean, table, array), mise returns this error because the templating layer expects string values.

Source

Thrown at src/backend/aqua.rs:3440

/// A failed verification may become valid after resolving a repository transfer.
/// Only a verified attestation can skip the canonical-repository lookup.
fn attestation_needs_transfer_retry(
    result: &std::result::Result<bool, crate::github::sigstore::AttestationError>,
) -> bool {
    !matches!(result, Ok(true))
}

fn toml_value_to_string(value: &toml::Value) -> Option<String> {
    match value {
        toml::Value::String(s) => Some(s.clone()),
        _ => None,
    }
}

fn toml_string_var(key: &str, value: &toml::Value) -> Result<String> {
    match value {
        toml::Value::String(s) => Ok(s.clone()),
        value => bail!(
            "aqua var `{}` must be a string, got {}",
            key,
            toml_value_kind(value)
        ),
    }
}

fn toml_value_kind(value: &toml::Value) -> &'static str {
    match value {
        toml::Value::String(_) => "string",
        toml::Value::Integer(_) | toml::Value::Float(_) => "number",
        toml::Value::Boolean(_) => "boolean",
        toml::Value::Array(_) => "array",
        toml::Value::Table(_) => "object",
        toml::Value::Datetime(_) => "datetime",
    }
}

View on GitHub (pinned to afd2eddd3a)

Solutions

1. Quote the var value in the TOML config so it is a string: `vars.version = "3"`
2. Check which aqua var key is named in the message and inspect its declared type
3. Update mise if a recent registry change introduced the non-string var
4. If authoring embedded plugin options in build.rs input, wrap all values as strings before serialization

Example fix

# before (mise.toml / embedded plugin options)
[tools.aqua-vars]
version = 3

# after
[tools.aqua-vars]
version = "3"

// ensure every aqua var you configure is a string
function assertStringVars(vars) {
  for (const [k, v] of Object.entries(vars ?? {})) {
    if (typeof v !== "string") throw new Error(`aqua var '${k}' must be a string, got ${typeof v}`);
  }
}
assertStringVars(config["aqua-vars"]);

function isTomlStringVar(v) {
  return typeof v === "string";
}

try {
  await $`mise install`;
} catch (e) {
  const m = String(e).match(/aqua var `(\S+)` must be a string/);
  if (m) {
    // quote the offending var in mise.toml and retry
    console.error(`Fix mise.toml: quote the value of '${m[1]}'`);
  } else throw e;
}

When it happens

Trigger: Loading/generating an embedded aqua plugin (aqua.rs:3440, reached via build.rs codegen path) where a package's or registry's var entry in the TOML configuration is declared as a non-string value, e.g. `vars.version = 3` or `vars.enabled = true`.

Common situations: Hand-editing an aqua-related config and writing an unquoted number or boolean; a registry migration changed a var's type; TOML auto-typing turns `version = 1.0` into a float.

Related errors

• [history] in {} is not a table
• [history] exclude in {} is not an array
• backend must be a string or table
• expected `run` to be a string or array of strings
• {message}

AI-assisted analysis of jdx/mise@afd2eddd3a (2026-09-09). Data as JSON: /api/errors/a8fe9d5f60226e71. Report an issue: GitHub.