denoland/deno · error · Error

${prefix}Linter plugin name must start and end with a lowerc

Error message

${prefix}Linter plugin name must start and end with a lowercase letter.

What it means

Thrown by installPlugin() in cli/js/40_lint.js when the plugin name passes the /^[a-z-]+$/ character check but begins or ends with a hyphen. Leading/trailing hyphens would produce rule ids like "-plugin/rule" and "plugin-/rule", so they are rejected to keep ids clean.

Source

Thrown at cli/js/40_lint.js:494

  // When the plugin was loaded from a specifier (i.e. `lint.plugins` in the
  // config), prefix validation errors with it so the user knows which plugin
  // is misbehaving instead of getting an anonymous error.
  const prefix = typeof specifier === "string"
    ? `Failed to load lint plugin '${specifier}': `
    : "";
  if (typeof plugin !== "object") {
    throw new Error(`${prefix}Linter plugin must be an object`);
  }
  if (typeof plugin.name !== "string") {
    throw new Error(`${prefix}Linter plugin name must be a string`);
  }
  if (!/^[a-z-]+$/.test(plugin.name)) {
    throw new Error(
      `${prefix}Linter plugin name must only contain lowercase letters (a-z) or hyphens (-).`,
    );
  }
  if (plugin.name.startsWith("-") || plugin.name.endsWith("-")) {
    throw new Error(
      `${prefix}Linter plugin name must start and end with a lowercase letter.`,
    );
  }
  if (plugin.name.includes("--")) {
    throw new Error(
      `${prefix}Linter plugin name must not have consequtive hyphens.`,
    );
  }
  if (typeof plugin.rules !== "object") {
    throw new Error(`${prefix}Linter plugin rules must be an object`);
  }
  if (state.installedPlugins.has(plugin.name)) {
    throw new Error(`Linter plugin ${plugin.name} has already been registered`);
  }
  state.plugins.push(plugin);
  state.installedPlugins.add(plugin.name);

  return {

View on GitHub (pinned to 89f33cbef2)

Solutions

1. Remove the leading/trailing hyphen so the name starts and ends with a lowercase letter
2. If you wanted a namespace prefix, fold it into the name with an inner hyphen, e.g. "internal-plugin"

Example fix

// before
export default { name: "-internal-plugin", rules: {} };

// after
export default { name: "internal-plugin", rules: {} };

function assertNoEdgeHyphens(name) {
  if (name.startsWith("-") || name.endsWith("-")) {
    throw new TypeError(`'${name}' must start and end with a lowercase letter`);
  }
}

function hasNoEdgeHyphens(name) {
  return !name.startsWith("-") && !name.endsWith("-");
}

When it happens

Trigger: A plugin `name` like "-my-plugin" or "my-plugin-". Only fires after the character-set check passes, so the name is otherwise lowercase/hyphen only but has an edge hyphen.

Common situations: Renaming a plugin with a scope-like prefix ("-internal-plugin") to mark it private; a typo adding a trailing hyphen while editing the name string.

Related errors

• ${prefix}Linter plugin name must only contain lowercase lett
• ${prefix}Linter plugin name must not have consequtive hyphen
• ${prefix}Linter plugin rules must be an object
• Linter plugin ${plugin.name} has already been registered
• Visitor "${name}" of plugin "${id}" errored

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/b1a56e22209271a7. Report an issue: GitHub.