Empty String Checker (ESLint Rule)

This repository provides an ESLint rule that disallows empty string literals in runtime/value contexts for TypeScript and JSX/TSX. The rule integrates directly into your ESLint setup.

Installation

Ensure you have ESLint and the TypeScript ESLint parser/utilities installed. With Bun:

bun add -d eslint @typescript-eslint/parser @typescript-eslint/utils typescript

Then add this repository's plugin/rule to your project as appropriate (publish or local path depending on your workflow).

Usage

Extend your ESLint configuration to include the rule. Example (flat config):

// eslint.config.mjs
import tsEslint from "typescript-eslint";
import plugin from "./rules/index.js"; // or your published package entry

export default tsEslint.config([
  {
    plugins: {
      "ubiquity-os": plugin,
    },
    rules: {
      "ubiquity-os/no-empty-strings": [
        "warn",
        {
          checkWhitespaceOnly: false,
          checkNoSubstitutionTemplates: true,
          ignoreZeroWidth: false,
          allowContexts: [],
        },
      ],
    },
  },
]);

Rule key: ubiquity-os/no-empty-strings

Options

All options are optional. Defaults shown.

• checkWhitespaceOnly (boolean, default false)

  • When true, whitespace-only strings (e.g., " ") are also reported.

• checkNoSubstitutionTemplates (boolean, default true)

  • When true, empty no-substitution template literals (``````) are reported.

• ignoreZeroWidth (boolean, default false)

  • When true, strings consisting only of zero-width characters (e.g., \u200B, \u200C, \u200D, \u200E, \u200F, \uFEFF) are ignored.

• allowContexts (string[], default [])

  • Array of AST node types in whose context empty strings should be allowed. Any ancestor node type matching an entry will allow the empty string.

Notes:

• Type-only positions (e.g., type A = "") and import/export specifiers are not reported.
• JSX attribute expressions like <Comp title={expr} /> are not reported; string literal attributes like <Comp title="" /> are reported.

Examples

Valid:

const a = "x";
const a = `${x}`;
type A = "";
<Comp title={expr} />

Invalid:

const a = "";
const a = myString ?? '';
const a = myString ? myString : '';
const a = ``; // when checkNoSubstitutionTemplates: true
<Comp title=""/>

With checkWhitespaceOnly: true:

const a = "   "; // invalid

Development

Prerequisites

• Bun
• TypeScript

Install dependencies

bun install

Run tests

bun test

This runs the ESLint RuleTester-based tests in tests/empty-string-eslint-rule.test.ts.

Lint and format

bun run format