Forbid returning too long tuples

[orsinium]

Rule request

Thesis

Forbid returning a too long constant-length tuple from a function:

# bad
def hello():
  return 1, 2, 3, 4

When there are more than 2 values must be returned, use dataclasses.dataclass, typing.NamedTuple, or attrs instead.

Reasoning

Code readability and maintainability: the caller code must know exact order of all components which is easy to mess up. A real-world example:

time, phase, spacing, size, version, error, series_type = read_result_log()

😩

[sobolevn]

We already have:

wemake-python-styleguide/wemake_python_styleguide/violations/complexity.py

Line 883 in 2214832

class TooLongYieldTupleViolation(ASTViolation):

and

wemake-python-styleguide/wemake_python_styleguide/violations/complexity.py

Line 1153 in 2214832

class TooLongTupleUnpackViolation(ASTViolation):

Maybe it is a good idea to simplify them into a single rule.

On the other hand, I like to define long immutable sequences as tuples. I guess that this should be allowed.

[orsinium]

Hmm. I tried the snippet above on flakehell.orsinium.dev and it hasn't found anything 🤔 I'm wondering what I did wrong.

[orsinium]

Oh, I see, it's only about yield, not return

On the other hand, I like to define long immutable sequences as tuples. I guess that this should be allowed.

Sure. This is why I said "constant-length". When you use a tuple as an immutable list (when the length is unknown in advance), it is fine.

[uhbif19]

@sobolevn So am I understanding correctly, that the issue realization must just add full TooLongYieldTupleViolation analog but working with return?

[orsinium]

Exactly! I don't see a reason why return is any different from yield from this perspective :)

[uhbif19]

Please assign me, I am finishing PR for this task.