No format string => no formatting

[jsumners]

The following makes no sense because there are not any format identifiers in the format string:

format('foo', ['bar']) // => 'foo bar'

The following doesn't make any sense because invoking a function is not the same thing as using the apply prototype method:

format(['%s', 'foo']) // => 'foo'

This PR removes these nonsense use cases such that:

1. yields: 'foo'
2. yields: null

This PR also makes the behavior match the documentation. No where in the docs does it enumerate the currently implemented surprising behaviors.

If this PR is accepted it will resolve https://github.com/pinojs/pino/issues/793

This PR will clearly necessitate a semver major release.

[jsumners]

ping: @davidmarkclements @mcollina

[jsumners]

Well it doesn't exactly match console.log:

❯ node
Welcome to Node.js v12.14.1.
Type ".help" for more information.
> console.log('foo', ['bar'])
foo [ 'bar' ]
undefined
> console.log('foo', [{}])
foo [ {} ]
undefined
>

Nor does it match Winston (https://runkit.com/embed/n0w7euy6ewl4):

{\"level\":\"info\",\"message\":\"foo\"}"

But it does match the odd man out, Bunyan:

❯ node
Welcome to Node.js v12.14.1.
Type ".help" for more information.
> var log = require('bunyan').createLogger({name:'logger'})
undefined
> log.info('foo', {})
{"name":"logger","hostname":"Jamess-MBP","pid":74872,"level":30,"msg":"foo {}","time":"2020-03-20T23:02:24.599Z","v":0}
undefined
>

I argue that this just makes no sense. No format tokens have been passed. Thus, no formatting should occur.

[jsumners]

Are you suggesting a semver patch PR to add documentation for the surprising behavior?

[mcollina]

I guess I’m asking if this PR matches the behavior documented in the readme.

[jsumners]

It’s does.

[jsumners]

@mcollina can you merge and release this and #28? Or do we need to wait on @davidmarkclements?

[mcollina]

I'll wait for Dave if possible.

[jsumners]

😞 I hope he responds soon. I'm blocked on this with no way of patching around it since this module is invoked in the LOG function and it's directly referenced instead of used as a pluggable module (e.g. format(...) instead of this[formatterSym](...)).

[davidmarkclements]

v4.0.0 released

[jsumners]

Thank you very much @davidmarkclements !