handlebars-lang/handlebars.js · error · Handlebars.Exception

Unable to minimize simple output

Error message

Unable to minimize simple output

What it means

The precompiler CLI throws when --simple (-s) and --min (-m) are combined. Simple mode emits a bare anonymous template function, which cannot be minimized since minification requires the full registry wrapper format.

Source

Thrown at lib/precompiler.js:168

      }
    }
  );
}

export async function cli(opts) {
  if (opts.version) {
    console.log(Handlebars.VERSION);
    return;
  }

  if (!opts.templates.length && !opts.hasDirectory) {
    throw new Handlebars.Exception(
      'Must define at least one template or directory.'
    );
  }

  if (opts.simple && opts.min) {
    throw new Handlebars.Exception('Unable to minimize simple output');
  }

  const multiple = opts.templates.length !== 1 || opts.hasDirectory;
  if (opts.simple && multiple) {
    throw new Handlebars.Exception(
      'Unable to output multiple templates in simple mode'
    );
  }

  // Force simple mode if we have only one template and it's unnamed.
  if (opts.templates.length === 1 && !opts.templates[0].name) {
    opts.simple = true;
  }

  // Convert the known list into a hash
  let known = {};
  if (opts.known && !Array.isArray(opts.known)) {
    opts.known = [opts.known];

View on GitHub (pinned to 13a7a67991)

Solutions

1. Remove the -s/--simple flag to keep minimization
2. Remove the -m/--min flag if bare simple output is required

Example fix

// before
handlebars -s -m src/templates/ -f dist/tpl.js

// after (keep minification)
handlebars src/templates/ -f dist/tpl.js --min
// or (keep simple mode)
handlebars -s src/templates/ -f dist/tpl.js

if (flags.simple && flags.min) {
  throw new Error('Cannot combine --simple and --min in the handlebars CLI');
}

try {
  execSync(cliCmd);
} catch (e) {
  if (/Unable to minimize simple output/.test(e.message)) {
    // drop -s or -m from the script and rerun
  } else throw e;
}

When it happens

Trigger: Running `handlebars -s -m templates/` or an npm script/CI config that sets both flags.

Common situations: Copying an existing script and toggling flags without knowing they are mutually exclusive; enabling minification for smaller bundles without realizing simple mode was already on.

Related errors

• Must define at least one template or directory.
• Unable to output multiple templates in simple mode
• Name missing for template
• Invalid stack pop
• Must pass iterator to #each

AI-assisted analysis of handlebars-lang/handlebars.js@13a7a67991 (2026-09-02). Data as JSON: /api/errors/26702dbaac9eb73d. Report an issue: GitHub.