Prettyprinter does not print dataclass default values

[pynista]

• PrettyPrinter version: 0.18.0
• Python version: 3.7.5
• Operating System: Ubuntu 16.04.6 LTS

Description

Prettyprinter does not print dataclass default values

What I Did

# script.py
from dataclasses import dataclass

import prettyprinter


@dataclass
class Car:
    model: str
    year: int
    owner: str = "Elon Musk"


opel_astra_2002 = Car('Opel Astra', 2002)

prettyprinter.install_extras(
    include=['dataclasses', ],
    warn_on_error=True
)
prettyprinter.pprint(opel_astra_2002)
print('Owner: {}'.format(opel_astra_2002.owner))

Script prints:

Car(model='Opel Astra', year=2002)
Owner: Elon Musk

[gsauthof]

I can see that it can be advantageous for some use-cases to have default-valued fields excluded from the pretty-print.

But it would also be great to be able to configure this aspect of the dataclasses pretty-printing.

Relevant code where fields with default values are excluded:

prettyprinter/prettyprinter/extras/dataclasses.py

Lines 32 to 50 in 53ba5f9

	display_attr = False
	if (
	field_def.default is MISSING and
	field_def.default_factory is MISSING
	):
	display_attr = True
	elif field_def.default is not MISSING:
	if field_def.default != getattr(value, field_def.name):
	display_attr = True
	elif field_def.default_factory is not MISSING:
	default_value = field_def.default_factory()
	if default_value != getattr(value, field_def.name):
	display_attr = True
	else:
	assert "default and default_factory should not be both defined"
	if display_attr:
	kwargs.append((field_def.name, getattr(value, field_def.name)))

[sigprof]

The same thing also happens with attrs classes.