linera-io/linera-protocol · error

unknown output format `{other}` (expected json|yaml|md|brief

Error message

unknown output format `{other}` (expected json|yaml|md|brief)

What it means

The format token of an --output spec is not one of the four supported formats. Each spec is FORMAT:TARGET and the format must be exactly json, yaml, md, or brief (case-sensitive); anything else fails before the target path is touched.

Source

Thrown at linera-service/src/cli/validator_benchmark/report.rs:75

        }
        if out.is_empty() {
            return Err(anyhow!("--output specified but resolved to no entries"));
        }
        Ok(out)
    }

    fn parse_one(s: &str) -> Result<OutputSpec> {
        let (fmt_str, target) = match s.split_once(':') {
            Some((f, p)) => (f, Target::File(PathBuf::from(p))),
            None => (s, Target::Stdout),
        };
        let format = match fmt_str {
            "json" => Format::Json,
            "yaml" => Format::Yaml,
            "md" => Format::Md,
            "brief" => Format::Brief,
            other => {
                return Err(anyhow!(
                    "unknown output format `{other}` (expected json|yaml|md|brief)"
                ))
            }
        };
        Ok(OutputSpec { format, target })
    }
}

/// Top-level benchmark report.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Report {
    pub metadata: Metadata,
    pub layers: Layers,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Metadata {
    pub tool_version: String,

View on GitHub (pinned to 6c226ddcb3)

Solutions

1. Use one of the exact lowercase tokens: json, yaml, md, brief.
2. Remember yml is not accepted — spell it yaml.
3. Keep the FORMAT:TARGET shape with a single colon (a path with a drive letter or extra colons will confuse the split).
4. Check the flag for stray whitespace between the format and the colon.

Example fix

# before
--output csv:report.csv
--output JSON:report.json

# after
--output json:report.json
--output md:report.md

fn is_known_output_format(s: &str) -> bool {
    matches!(s, "json" | "yaml" | "md" | "brief")
}

fn is_known_output_format(s: &str) -> bool {
    matches!(s, "json" | "yaml" | "md" | "brief")
}

When it happens

Trigger: `--output csv:report.csv`, capitalized tokens like `JSON:report.json`, or a spec missing its separator so the whole string lands in the format slot.

Common situations: Assuming a generic format list; copy-pasting output flags from a different tool; typos like 'yml' instead of 'yaml' or 'markdown' instead of 'md'.

Related errors

• --output specified but resolved to no entries
• Validator spec must be in format: public_key,account_key,add
• --bulk-height-range must be `auto` or `FROM:TO`
• expected query to start with 'query', got: {s}
• expected whitespace after 'query' keyword

AI-assisted analysis of linera-io/linera-protocol@6c226ddcb3 (2026-08-22). Data as JSON: /api/errors/7dc5c56c4b2213dc. Report an issue: GitHub.