swc-project/swc · error

--watch requires input files

Error message

--watch requires input files

What it means

The SWC CLI's validate() rejects a --watch invocation that names no input files: watch mode needs at least one entry in `files` to know what to compile and re-compile on change. Raised via bail! before any compilation starts, so nothing is processed.

Source

Thrown at crates/swc_cli_impl/src/commands/compile.rs:513

                "true" => SourceMapsConfig::Bool(true),
                value => SourceMapsConfig::Str(value.to_string()),
            });

            self.source_file_name
                .clone_into(&mut options.source_file_name);
            self.source_root.clone_into(&mut options.source_root);
        }

        Ok(options)
    }

    fn validate(&self) -> anyhow::Result<()> {
        if self.watch && self.out_file.is_none() && self.out_dir.is_none() {
            bail!("--watch requires --out-file or --out-dir");
        }

        if self.watch && self.files.is_empty() {
            bail!("--watch requires input files");
        }

        if self.copy_files && self.out_dir.is_none() {
            bail!("--copy-files requires --out-dir");
        }

        if self.strip_leading_paths && self.out_dir.is_none() {
            bail!("--strip-leading-paths requires --out-dir");
        }

        Ok(())
    }

    fn included_extensions(&self) -> Vec<String> {
        self.extensions.clone().unwrap_or_else(|| {
            DEFAULT_EXTENSIONS
                .iter()
                .map(|value| value.to_string())

View on GitHub (pinned to 5176682b65)

Solutions

1. Provide the paths to watch: `swc -w ./src -d dist`
2. Check scripts for unquoted/empty variables passed to swc

Example fix

# before
swc --watch -d dist
# after
swc --watch ./src -d dist

# Shell - enforce watch input precondition
if [[ "$WATCH" == "1" && ${#INPUTS[@]} -eq 0 ]]; then
  echo "--watch requires input files" >&2; exit 1;
fi

When it happens

Trigger: Running `swc -w -d dist` with no positional inputs; a variable intended to hold paths expanding to nothing in an npm script.

Common situations: CI/scripts where the file list variable is empty; assuming watch uses a .swcrc-declared entry (it does not - entries come from CLI args).

Related errors

• --watch requires --out-file or --out-dir
• --copy-files requires --out-dir
• --strip-leading-paths requires --out-dir
• Input is empty
• `{raw}` is not a valid ecmascript version

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/6d35e474e177b034. Report an issue: GitHub.