What causes "{format} format not supported" in jdx/mise?

Choose a differently compressed asset (e.g. .gz, .xz, .zst, .bz2) for the tool version

format not supported

Error message

{format} format not supported

What it means

decompress_file supports single-file decompression only for gz, xz, zst, and bz2. Passing Br (brotli), Lz4, or Sz (snappy) as the format bails with "{format} format not supported" — these formats are recognized in the enum but no decompressor is wired in for single-file use.

Solutions

Choose a differently compressed asset (e.g. .gz, .xz, .zst, .bz2) for the tool version
Decompress the file yourself with a dedicated tool (brotli -d, lz4 -d, snunzip) into dest before/instead of calling decompress_file
If this is inside a backend, change the asset URL or format mapping to a supported compression
Add an actual decompressor integration upstream if brotli/lz4/snappy single-file support is genuinely needed

Example fix

// before
format = ExtractionFormat::from_ext("lz4")?; // decompress_file -> error
// after
format = ExtractionFormat::from_ext("gz")?; // or decompress externally first

Defensive patterns

Strategy: fallback

Validate before calling

if matches!(fmt, ExtractionFormat::Br | ExtractionFormat::Lz4 | ExtractionFormat::Sz) {
    // decompress externally or pick a supported asset
}

Try / catch

match decompress_file(&input, &dest, fmt) {
    Err(e) if e.to_string().contains("format not supported") => {
        // fallback: shell out to `brotli -d` / `lz4 -d` or download a gz/xz/zst/bz2 asset
    }
    other => other?,
}

Prevention

Only call decompress_file for gz/xz/zst/bz2 assets
Check ExtractionFormat::is_compressed_file() plus explicit Br/Lz4/Sz exclusion first
Prefer release assets in supported compressions when configuring backends
Keep a external-decompressor fallback for brotli/lz4/snappy

When it happens

Trigger: Calling decompress_file(input, dest, ExtractionFormat::Br | Lz4 | Sz), typically after ExtractionFormat::from_file_name classified a downloaded .br/.lz4/.sz single-file asset.

Common situations: Downloading a brotli- or lz4-compressed binary from a tool release and letting mise decompress it; backend config pointing at a .lz4 asset where only tar.lz4-style support was assumed.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/a90866c084e27d3c. Report an issue: GitHub.

Appendix: source

Thrown at src/file.rs:1974

        }
        _ => f(),
    }
}

pub(crate) fn decompress_file(input: &Path, dest: &Path, format: ExtractionFormat) -> Result<()> {
    if let Some(parent) = dest.parent()
        && !parent.as_os_str().is_empty()
    {
        create_dir_all(parent)?;
    }

    run_blocking(|| match format {
        ExtractionFormat::Gz => un_gz(input, dest),
        ExtractionFormat::Xz => un_xz(input, dest),
        ExtractionFormat::Zst => un_zst(input, dest),
        ExtractionFormat::Bz2 => un_bz2(input, dest),
        ExtractionFormat::Br | ExtractionFormat::Lz4 | ExtractionFormat::Sz => {
            bail!("{format} format not supported")
        }
        _ => bail!("unsupported compressed file format: {}", format),
    })
}

#[derive(Debug, Clone, Copy, PartialEq, strum::EnumString, strum::Display)]
pub(crate) enum ExtractionFormat {
    #[strum(to_string = "tar.gz", serialize = "tgz")]
    TarGz,
    #[strum(serialize = "gz")]
    Gz,
    #[strum(to_string = "tar.xz", serialize = "txz")]
    TarXz,
    #[strum(serialize = "xz")]
    Xz,
    #[strum(to_string = "tar.bz2", serialize = "tbz2", serialize = "tbz")]
    TarBz2,
    #[strum(serialize = "bz2")]

View on GitHub (pinned to 533346cc37)