Package Exports

@mjfwebb/enforce-logger-snake-case
@mjfwebb/enforce-logger-snake-case/dist/index.js

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Readme

@mjfwebb/enforce-logger-snake-case

An ESLint plugin that enforces snake_case naming convention for object keys passed to Logger methods, ensuring consistent and predictable logging throughout your codebase.

Installation

npm install --save-dev @mjfwebb/enforce-logger-snake-case

Usage

ESLint Flat Config (`eslint.config.js`)

import enforceLoggerSnakeCase from "@mjfwebb/enforce-logger-snake-case";

export default [
  {
    plugins: {
      "enforce-logger-snake-case": enforceLoggerSnakeCase,
    },
    rules: {
      // Enforce snake_case keys in Logger method calls
      "enforce-logger-snake-case/enforce-logger-snake-case": "error",
    },
  },
];

Legacy config (`.eslintrc.cjs`)

module.exports = {
  plugins: ["enforce-logger-snake-case"],
  rules: {
    "enforce-logger-snake-case/enforce-logger-snake-case": "error",
  },
};

Rule: enforce-logger-snake-case/enforce-logger-snake-case

Enforces snake_case naming convention for object keys when passing objects to Logger methods.

This rule applies to the following Logger methods:

Logger.trace()
Logger.debug()
Logger.info()
Logger.warn()
Logger.error()

Examples

❌ Incorrect

// camelCase and PascalCase keys
Logger.info({ userId: 123 });

Logger.debug({ requestCount: 5 });

Logger.error({ errorMessage: "failed", ErrorCode: 500 });

Logger.warn({ connectionTimeout: 30 });

Logger.trace({ APIResponseTime: 100 });

// Mixed naming conventions
Logger.info({
  user_id: 1,
  userName: "test", // camelCase not allowed
  userEmail: "test@example.com", // camelCase not allowed
});

// Shorthand properties with camelCase variable names
const userId = 123;
Logger.info({ userId }); // will be converted to { user_id: userId }

// Quoted identifiers (even if already snake_case)
Logger.info({ "user_id": 123 }); // quotes should be removed for consistency

// Spread properties (cannot be validated)
Logger.info({ ...otherObject });
Logger.info({ user_id: 1, ...otherObject });

// Computed properties (cannot be validated)
const key = "user_id";
Logger.info({ [key]: 123 });
Logger.info({ [getUserIdKey()]: 123 });

✅ Correct

// Unquoted snake_case identifiers
Logger.info({ user_id: 123 });

Logger.debug({ request_count: 5 });

Logger.error({ error_message: "failed", error_code: 500 });

Logger.warn({ connection_timeout: 30 });

Logger.trace({ api_response_time: 100 });

// Single word keys are valid
Logger.info({ message: "test" });
Logger.debug({ status: "ok" });

// Multiple snake_case keys
Logger.info({
  user_id: 1,
  user_name: "test",
  user_email: "test@example.com",
});

// Shorthand properties with snake_case variable names
const user_id = 123;
Logger.info({ user_id });

// String literals with special characters (allowed since they can't be identifiers)
Logger.info({ "user-id": 123 });
Logger.info({ "Content-Type": "application/json" });

// Other loggers are not affected
console.log({ userId: 123 });
someOtherLogger.info({ userId: 123 });

// Non-object arguments are allowed
Logger.info("simple message");
Logger.info(123);
Logger.info();

Auto-fix

This rule includes an automatic fix that converts camelCase and PascalCase keys to snake_case:

// Before (auto-fix)
Logger.info({ userId: 123, requestCount: 5 });

// After (auto-fix applied)
Logger.info({ user_id: 123, request_count: 5 });

Shorthand properties are expanded when needed:

// Before (auto-fix)
const userId = 123;
Logger.info({ userId });

// After (auto-fix applied)
const userId = 123;
Logger.info({ user_id: userId });

Quoted identifiers are unquoted:

// Before (auto-fix)
Logger.info({ "user_id": 123 });
Logger.info({ "userId": 456 });

// After (auto-fix applied)
Logger.info({ user_id: 123 });
Logger.info({ user_id: 456 });

Run ESLint with the --fix flag to automatically convert all keys to snake_case:

eslint --fix .

Rule Details

This rule enforces several constraints for consistent logging:

snake_case required: All property names must use snake_case (lowercase with underscores)
No quoted identifiers: Property names that could be valid identifiers must not be quoted
No spread properties: Spread syntax (...object) is not allowed as properties cannot be validated
No computed properties: Computed property names ([key]) are not allowed as they cannot be validated at lint time

Notes

Only applies to objects passed directly as the first argument to Logger methods
Does not affect other logging libraries or console methods
Snake_case format: lowercase letters and numbers, with underscores separating words
Single word keys (all lowercase) are valid
Valid pattern: ^[a-z][a-z0-9]*(?:_[a-z0-9]+)*$
Auto-fix converts camelCase and PascalCase to snake_case (e.g., userId → user_id, APIResponseTime → api_response_time)
String literals with special characters (hyphens, spaces, etc.) are allowed since they require quotes

License

MIT