Black should enforce zero empty leading lines in function body

[rogalski]

Operating system: playground
Python version: playground
Black version: master

Consider following code snippet:

class X:
    
    
    def f(self, x):
        
        
        return x**2

When class definition is formatted, empty lines between class X: line and first node of the body is forced to be zero.
When function definition is formatted, empty lines between def f(): line and first node of the body is normalised to either 0 (if input code had 0 empty lines) or 1 (if input code had 1+ empty lines).

While it's preferable to preserve some of the empty lines of input code, doing this for leading empty lines of node body makes no sense, as this empty line cannot have any mental meaning in such context.

[felix-hilden]

I would assume this should also apply to classes, and I'd go as far as to say that all blocks should have their leading vertical whitespace removed, for example:

if a:

    b

But they could surely be taken care of in separate issues. More like a mental note for now.

[tolomea]

That sounds right I can't think of any reason to have blank lines around an increase in indent level, the increase it self is quite visually clear.
It's a bit different with dedents which often end logical blocks.

[jenstroeger]

I’m a bit late to the discussion, but I still wanted to chime in after a few empty lines were removed with which I quite disagree. In general, yes the above makes sense for one exception: comments.

If I start a code block with a comment then I always have an empty line before; it makes reading easier:

def some_function():
    """Does something nifty."""
    
    # And here we go with the first code block.
    if condition:

        # And more explanation here because this next code block is funky.
        foo = ...

With merging PR #3035, however, this is all being squashed and mushed and compacted together which makes the code unreadable. It also defeats the purpose of comments separating code blocks:

def some_function():
    """Does something nifty."""
    # And here we go with the first code block.
    if condition:
        # And more explanation here because this next code block is funky.
        foo = ...

Any chance this all can be loosened up some?

[bluenote10]

The original post is slightly misleading, because multiple empty lines at the beginning of a block is certainly odd, and something black has prevented for a long time already. See #3551 for some "objective" (as far as one can get) arguments why allowing either zero or one empty line can have advantages from a typographic / design perspective.