Support functional API for Enum creation

[gvanrossum]

The enum.Enum class (new in Python 3.4, also backported as enum34) supports several short forms of creating an Enum type, described under functional API:

A = Enum('A', 'x y z')
B = Enum('B', ('p', 'q'))

These are equivalent to

class A(Enum):
    x = 1
    y = 2
    z = 3
class B(Enum):
    p = 1
    q = 2

Some other syntactic variants are also allowed:

A = Enum('A', 'x,y,z')
A = Enum('A', 'x, y, z')
B = Enum('B', ['p', 'q'])

The values can also be expressed as a list of tuples:

[('cyan', 4), ('magenta', 5), ('yellow', 6)]

or a mapping:

{'chartreuse': 7, 'sea_green': 11, 'rosemary': 42}

[homeworkprod]

I've been checking out mypy for less than two minutes, stumbled upon the error (Too many arguments for "Enum") with the first few files to check, searched the web, and followed a trail of issues to find out that this is at least known.

Yeah, I'd like to see this fixed rather sooner than later. This might drive new users away right at the start.

Until then, is there a way to suppress the error and keep mypy from exiting with a return code > 0 (for use in CI scripts)?

[JukkaL]

@homeworkprod The recommended fix is to refactor your code to use an alternative enum syntax. Is that not feasible for some reason? If not, I'd like to hear about your concerns. You can also try adding # type: ignore to silence the message.

@gvanrossum What do you think about making this a high priority issue? Multiple users seem to be hitting this, and this shouldn't be hard to support (though the implementation will be pretty tedious to write).

[gvanrossum]

Agreed.

[homeworkprod]

@JukkaL Well, I highly prefer the (oftentimes) one-liner functional API to spreading the definition of a (smaller) enum over multiple lines and including distracting, somewhat error-prone numbers that are irrelevant for the business logic (in the cases in question). Why have (to read) half a page of code when three lines neatly do the trick?

The ignore hint works for me, so I'll go with that for now, thank you.