@serejke/eslint-plugin-pino-enforce-static-message

ESLint rule to enforce static log messages for Pino loggers. Ensures dynamic data is passed via context objects for proper log aggregation and querying.

Why?

Dynamic log messages break log aggregation tools:

// BAD - Each unique userId creates a separate log entry type
logger.info(`User ${userId} logged in`);

// GOOD - All logins group under "User logged in"
logger.info({ userId }, 'User logged in');

Installation

npm install --save-dev @serejke/eslint-plugin-pino-enforce-static-message
# or
pnpm add -D @serejke/eslint-plugin-pino-enforce-static-message

Usage

Flat Config (ESLint 9+)

// eslint.config.js
import pinoEnforceStaticMessage from '@serejke/eslint-plugin-pino-enforce-static-message';

export default [
  {
    plugins: {
      '@serejke/pino-enforce-static-message': pinoEnforceStaticMessage,
    },
    rules: {
      '@serejke/pino-enforce-static-message/enforce-static-message': 'error',
    },
  },
];

With Options

rules: {
  '@serejke/pino-enforce-static-message/enforce-static-message': ['error', {
    allowInTests: true,
    testFilePatterns: ['**/*.test.ts', '**/test/**/*.ts'],
    excludeMethods: ['child', 'flush'],
  }],
}

Rule: enforce-static-message

What it checks

1. Static message enforcement: Log messages must be string literals
2. Error key convention: Error objects must use err as the key name (Pino convention)

Valid

// Static message only
logger.info('Server started');

// Context object + static message
logger.info({ userId, action }, 'User action recorded');

// Error with 'err' key
logger.error({ err: error, requestId }, 'Request failed');

// Child logger (exempt from checks)
const childLogger = logger.child({ module: moduleName });

Invalid

// Template literal
logger.info(`Processing ${count} items`);
// Error: Log message must be a static string literal

// String concatenation
logger.error('Failed: ' + error.message);
// Error: Log message must be a static string literal

// Wrong key for Error
logger.error({ error: e }, 'Failed');
// Error: Use 'err' as the key name for Error objects
// Auto-fixed to: logger.error({ err: e }, 'Failed');

Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | allowInTests | boolean | true | Skip rule in test files | | testFilePatterns | string[] | ['**/*.test.ts', '**/*.spec.ts', '**/__tests__/**/*.ts'] | Glob patterns for test files | | additionalMethods | string[] | [] | Additional method names to check | | excludeMethods | string[] | ['child'] | Method names to exclude from checking |

Checked Methods

By default, the rule checks these Pino log methods:

• trace()
• debug()
• info()
• warn()
• error()
• fatal()

Auto-fix

The rule provides auto-fix for the error → err key rename:

// Before
logger.error({ error: e }, 'Failed');

// After auto-fix
logger.error({ err: e }, 'Failed');

License

MIT