denoland/deno · error · Error

Linter plugin name must start and end with a lowercase…

Error message

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

What it means

After the charset check, Deno's lint plugin loader also rejects plugin names whose first or last character is a hyphen (plugin.name.startsWith("-") || plugin.name.endsWith("-") in cli/js/40_lint.js). The rule exists so names are always parseable as kebab-case tokens inside rule ids like "plugin-name/rule-name". The message is prefixed with "Failed to load lint plugin '<specifier>': " when the plugin came from a specifier.

Solutions

1. Remove the leading or trailing hyphen so the name starts and ends with a lowercase letter ("my-plugin").
2. If the name is generated, trim '-' from both ends: name.replace(/^-+|-+$/g, "").
3. Re-run `deno lint` to confirm the plugin installs.

Example fix

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

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

function normalizePluginName(name) {
  return String(name).replace(/[^a-z-]+/g, "-").replace(/^-+|-+$/g, "");
}
const plugin = { name: normalizePluginName(rawName), rules };

/** @param {unknown} name @returns {boolean} */
function hasCleanNameEdges(name) {
  return typeof name === "string" && /^[a-z](.*[a-z])?$/.test(name);
}

try {
  installPlugin(plugin);
} catch (err) {
  if (err.message.includes("must start and end with a lowercase letter")) {
    plugin.name = plugin.name.replace(/^-+|-+$/g, ""); // then retry once
  } else throw err;
}

When it happens

Trigger: Installing a lint plugin whose `name` is "-my-plugin", "my-plugin-", or just "-". The name already passed /^[a-z-]+$/ (so it is only lowercase letters and hyphens) but has a leading or trailing hyphen.

Common situations: Hand-truncating a longer name and leaving a hyphen ("my-plugin" cut to "-plugin"); generating names by splitting a phrase on spaces and joining with '-' including empty parts; typos.

Related errors

• Linter plugin name must not have consequtive hyphens.
• Linter plugin name must only contain lowercase letters…
• Linter plugin rules must be an object
• Destroy hook of " " errored
• Empty node

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/b1a56e22209271a7. Report an issue: GitHub.

Appendix: 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 {

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