microsoft/edit · error

invalid language: "{}"

Error message

invalid language: "{}"

What it means

unicode-gen parses --lang with value_from_fn, accepting only "c" and "rust". Any other value is rejected with `invalid language: "{}"`. This guards generation of Unicode tables to the two supported source-language targets.

Source

Thrown at crates/unicode-gen/src/main.rs:266

  --no-ambiguous        Treat all ambiguous characters as narrow
  --line-breaks         Store and expose line break information

Download ucd.nounihan.grouped.xml at:
  https://www.unicode.org/Public/UCD/latest/ucdxml/ucd.nounihan.grouped.zip
";

fn main() -> anyhow::Result<()> {
    let mut args = pico_args::Arguments::from_env();
    if args.contains(["-h", "--help"]) {
        eprint!("{HELP}");
        return Ok(());
    }

    let mut out = Output {
        arg_lang: args.value_from_fn("--lang", |arg| match arg {
            "c" => Ok(Language::C),
            "rust" => Ok(Language::Rust),
            l => bail!("invalid language: \"{}\"", l),
        })?,
        arg_extended: args.contains("--extended"),
        arg_no_ambiguous: args.contains("--no-ambiguous"),
        arg_line_breaks: args.contains("--line-breaks"),
        ..Default::default()
    };
    let arg_input = args.free_from_os_str(|s| -> Result<PathBuf, &'static str> { Ok(s.into()) })?;
    let arg_remaining = args.finish();
    if !arg_remaining.is_empty() {
        bail!("unrecognized arguments: {:?}", arg_remaining);
    }

    let input = std::fs::read_to_string(arg_input)?;
    let doc = roxmltree::Document::parse(&input)?;
    out.ucd = extract_values_from_ucd(&doc, &out)?;

    // Find the best trie configuration over the given block sizes (2^2 - 2^8) and stages (4).
    // More stages = Less size. The trajectory roughly follows a+b*c^stages, where c < 1.

View on GitHub (pinned to 826b4c097b)

Solutions

1. Use --lang c or --lang rust exactly (lowercase).
2. If you need another target, extend the match arm in main.rs to map the new string to a Language variant.
3. Check the binary's usage/help for the supported language list.

Example fix

// before
unicode-gen --lang=cpp GraphemeBreakProperty.txt
// after
unicode-gen --lang=c GraphemeBreakProperty.txt

const SUPPORTED: &[&str] = &["c", "rust"];
let lang = std::env::args().find(|a| a.starts_with("--lang")).map(|a| a.split('=').nth(1).unwrap_or("")).unwrap_or("");
assert!(SUPPORTED.contains(&lang), "--lang must be c or rust, got {lang}");

When it happens

Trigger: Running unicode-gen with --lang set to anything other than `c` or `rust`, e.g. --lang=cpp, --lang=python, or a misspelling like --lang=Rust (case-sensitive).

Common situations: Assuming other output languages are supported; shell completion offering stale values; case mistakes since the matcher is exact lowercase.

Understand the failure class

Background: "invalid argument", "unknown mode", "not supported": invalid enum-like argument errors explained — this error's family across 19 libraries.

Related errors

• At least one .lsh file or directory is required
• A language ID is required when reading from stdin
• No highlighting definition found for language {language:?}
• No matching highlighting definition found
• unrecognized arguments: {:?}

AI-assisted analysis of microsoft/edit@826b4c097b (2026-09-06). Data as JSON: /api/errors/88ad6a5b003b70b7. Report an issue: GitHub.