evanw/esbuild · error · Error

Duplicated test name "${name}" in ${file}

Error message

Duplicated test name "${name}" in ${file}

What it means

In the terser-test parser (scripts/terser-tests.js:241), fixtures are keyed by label names; if two labeled statements at the top level share the same label name, the harness throws 'Duplicated test name'. This prevents ambiguous/overridden tests within a single terser compress fixture file. The quoted name and file identify the collision.

Source

Thrown at scripts/terser-tests.js:242

function parse_test(file) {
  var script = fs.readFileSync(file, "utf8");
  // TODO try/catch can be removed after fixing https://github.com/mishoo/UglifyJS2/issues/348
  try {
    var ast = U.parse(script, {
      filename: file
    });
  } catch (e) {
    console.log("Caught error while parsing tests in " + file + "\n");
    console.log(e);
    throw e;
  }
  var tests = {};
  var tw = new U.TreeWalker(function (node, descend) {
    if (node instanceof U.AST_LabeledStatement
      && tw.parent() instanceof U.AST_Toplevel) {
      var name = node.label.name;
      if (name in tests) {
        throw new Error('Duplicated test name "' + name + '" in ' + file);
      }
      tests[name] = get_one_test(name, node.body);
      return true;
    }
    if (!(node instanceof U.AST_Toplevel)) croak(node);
  });
  ast.walk(tw);
  return tests;

  function croak(node) {
    throw new Error(tmpl("Can't understand test file {file} [{line},{col}]\n{code}", {
      file: file,
      line: node.start.line,
      col: node.start.col,
      code: make_code(node, { beautify: false })
    }));
  }

View on GitHub (pinned to f6058f8364)

Solutions

1. Rename one of the duplicated labels so each test case in the file is uniquely named.
2. Regenerate the local `.terser-tests` fixtures from upstream terser to clear stale duplicates.

Example fix

// before — in one fixture file
foo_test: { ... }
foo_test: { ... }
// after
foo_test: { ... }
foo_test_2: { ... }

function assertUniqueTestNames(tests: Record<string, any>, file: string): void {
  const seen = new Set<string>();
  for (const name in tests) {
    if (seen.has(name)) throw new Error(`Duplicated test name "${name}" in ${file}`);
    seen.add(name);
  }
}

When it happens

Trigger: A terser compress fixture file containing two `label_name: { ... }` test cases with the identical label name.

Common situations: Copying a test case and forgetting to rename the label; merging fixture files that each used a generic name like `default`; upstream terser adding a name that already exists locally.

Related errors

• Unsupported input syntax
• Can't understand test file {file} [{line},{col}] {code}
• Should be boolean
• Should be array of strings
• Should be string or array of strings

AI-assisted analysis of evanw/esbuild@f6058f8364 (2026-08-09). Data as JSON: /api/errors/74bc45b4f30f9046. Report an issue: GitHub.