serialize should not be mandatory when defining a custom formatter

[TommyMoscatelli]

Which package?

cli-lib

Describe the bug

The current Formatter interface requires to define a custom serialize function.

export interface Formatter {
  serialize: SerializeFn
  format: FormatFn
  compile: CompileFn
  compareMessages?: Comparator
}

But the current code is already checking if serialize is a function, otherwise it applies the default serialization:

if (typeof formatter.serialize === 'function') {
  return formatter.serialize(formatter.format(results as any))
}
return stringify(formatter.format(results as any), {
  space: 2,
  cmp: formatter.compareMessages || undefined,
})

Expected behavior

To apply the default serialization, the formatter interface should be:

export interface Formatter {
  serialize?: SerializeFn
  format: FormatFn
  compile: CompileFn
  compareMessages?: Comparator
}

[longlho]

this should be fixed in latest version