[RFC] Convert the LumberjackLevel enum to a string literal union type

[LayZeeDK]

The LumberjackLevel enum is essential to Lumberjack. Since it will affect many packages in the future, I think that now is the best time to propose to convert it from a TypeScript enum to a string literal union type.

Pros

• Terser
• Decreased bundle size
• No need to import LumberjackLevel in most use cases
• Strong typing is maintained
• Auto-completion is maintained
• Refactoring is still supported except for a few edge cases:
  • String literal rename doesn't work with template literals microsoft/TypeScript#41922
  • String literal rename doesn't work in switch/case statment microsoft/TypeScript#41923
  • String literal rename doesn't work in object unions microsoft/TypeScript#41489
• Avoid a future const enum conversion which can lead to issues

Cons

• Breaking change
• Less explicit
• No support for Object.entries, Object.keys, or Object.values.

Breaking change

Before

Implementation

/**
 * Level used to configure log drivers or add a log level to a log.
 */
export enum LumberjackLevel {
  Critical = 'critical',
  Debug = 'debug',
  Error = 'error',
  Info = 'info',
  Trace = 'trace',
  Verbose = 'verbose',
  Warning = 'warn',
}

Internal usage

export const defaultProductionLevels: LumberjackConfigLevels = [
  LumberjackLevel.Critical,
  LumberjackLevel.Error,
  LumberjackLevel.Info,
  LumberjackLevel.Warning,
];

External usage

lumberjack.log({
  level: LumberjackLevel.Info,
  message: 'Hello, World!',
  scope: 'MyComponent',
  createdAt: Date.now(),
});

After

Implementation

/**
 * Level used to configure log drivers or add a log level to a log.
 */
export type LumberjackLevel = 'critical' | 'debug' | 'error' | 'info' | 'trace' | 'verbose' | 'warn';

Internal usage

export const defaultProductionLevels: LumberjackConfigLevels = ['critical', 'error', 'info', 'warning'];

External usage

lumberjack.log({
  level: 'info',
  message: 'Hello, World!',
  scope: 'MyComponent',
  createdAt: Date.now(),
});

[NachoVazquez]

I love it. It is a significant breaking change, but this is the moment for big changes.