denoland/deno · error

{} is not a valid UTF-8 file

Error message

{} is not a valid UTF-8 file

What it means

Error "{} is not a valid UTF-8 file" thrown in denoland/deno.

Source

Thrown at cli/tools/fmt.rs:1669

pub struct FileContents<'a> {
  pub text: Cow<'a, str>,
  pub had_bom: bool,
}

fn read_file_contents(file_path: &Path) -> Result<FileContents<'_>, AnyError> {
  let file_bytes = fs::read(file_path)
    .with_context(|| format!("Error reading {}", file_path.display()))?;
  let had_bom = file_bytes.starts_with(&[0xEF, 0xBB, 0xBF]);

  let charset =
    deno_media_type::encoding::detect_charset_local_file(&file_bytes);
  let text = deno_media_type::encoding::decode_owned_source(
    charset,
    file_bytes.to_vec(),
  )
  .with_context(|| {
    anyhow!("{} is not a valid UTF-8 file", file_path.display())
  })?;

  Ok(FileContents {
    text: Cow::Owned(text),
    had_bom,
  })
}

fn write_file_contents(
  file_path: &Path,
  file_contents: &str,
) -> Result<(), AnyError> {
  Ok(fs::write(file_path, file_contents)?)
}

pub async fn run_parallelized<F>(
  file_paths: Vec<PathBuf>,
  f: F,

View on GitHub (pinned to 89f33cbef2)

When it happens

Trigger: Thrown at cli/tools/fmt.rs:1669 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/da86954b6aee25c1. Report an issue: GitHub.