Re: [PATCH v7 06/10] iotests: limit line length to 79 chars

[Kevin Wolf]

Am 05.03.2020 um 19:25 hat John Snow geschrieben:
> On 3/5/20 6:55 AM, Kevin Wolf wrote:
> > Am 05.03.2020 um 00:14 hat John Snow geschrieben:
> >>
> >>
> >> On 3/4/20 4:58 PM, Philippe Mathieu-Daudé wrote:
> > 
> > Adding back the context:
> > 
> >> -        sys.stderr.write('qemu-img received signal %i: %s\n' % 
> >> (-exitcode, ' '.join(qemu_img_args + list(args))))
> >> +        sys.stderr.write('qemu-img received signal %i: %s\n' % (
> >> +            -exitcode, ' '.join(qemu_img_args + list(args))))
> > 
> >>> Do we want to indent Python like C and align argument below opening
> >>> parenthesis? Except when using sys.stderr.write() you seem to do it.
> >>
> >> This isn't an argument to write, it's an argument to the format string,
> >> so I will say "no."
> > 
> > The argument to write() is an expression. This expression contains the %
> > operator with both of its operands. It's still fully within the
> > parentheses of write(), so I think Philippe's question is valid.
> > 
> >> For *where* I've placed the line break, this is the correct indentation.
> >> emacs's python mode will settle on this indent, too.
> >>
> >> https://python.org/dev/peps/pep-0008/#indentation
> > 
> > The PEP-8 examples are not nested, so it's not completely clear. I
> > wonder if hanging indents wouldn't actually mean the following because
> > if you line wrap an argument list (which contains the whole %
> > expression), you're supposed to have nothing else on the line of the
> > opening parenthesis:
> > 
> >     sys.stderr.write(
> >         'qemu-img received signal %i: %s\n'
> >         % (-exitcode, ' '.join(qemu_img_args + list(args))))
> > 
> 
> This is fine too.
> 
> > But anyway, I think the question is more whether we want to use hanging
> > indents at all (or at least if we want to use it even in cases where the
> > opening parenthesis isn't already at like 70 characters) when we're
> > avoiding it in our C coding style.
> > 
> > There's no technical answer to this, it's a question of our preferences.
> > 
> 
> Maybe it is ambiguous. Long lines are just ugly everywhere.
> 
> >> (If anyone quotes Guido's belittling comment in this email, I will
> >> become cross.)
> >>
> >>
> >> But there are other places to put the line break. This is also
> >> technically valid:
> >>
> >> sys.stderr.write('qemu-img received signal %i: %s\n'
> >>                  % (-exitcode, ' '.join(qemu_img_args + list(args))))
> >>
> >> And so is this:
> >>
> >>     sys.stderr.write('qemu-img received signal %i: %s\n' %
> >>                      (-exitcode, ' '.join(qemu_img_args + list(args))))
> > 
> > PEP-8 suggests the former, but allows both styles:
> > 
> > https://www.python.org/dev/peps/pep-0008/#should-a-line-break-before-or-after-a-binary-operator
> > 
> 
> So in summary:
> 
> - Avoid nested hanging indents from format operators
> - Use a line break before the % format operator.
> - OPTIONALLY(?), use a hanging indent for the entire format string to
> reduce nesting depth.

Yes, though I don't think of it as a special case for format strings. So
I would phrase it like this:

- Don't use hanging indent for any nested parentheses unless the outer
  parentheses use hanging indents, too.
- Use a line break before binary operators.
- OPTIONALLY, use a hanging indent for the top level(s) to reduce
  nesting depth.

The first one is the only rule that involves some interpretation of
PEP-8, the rest seems to be its unambiguous recommendation.

Anyway, so I would apply the exact same rules to the following (imagine
even longer expressions, especially the last example doesn't make sense
with the short numbers):

* bad:
    really_long_function_name(-1234567890 + 987654321 * (
        1337 / 42))

* ok:
    really_long_function_name(-1234567890 + 987654321
                              * (1337 / 42))

* ok:
    really_long_function_name(
        -1234567890 + 987654321
        * (1337 / 42))

* ok:
    really_long_function_name(
        -1234567890 + 987654321 * (
            1337 / 42))

> e.g., either this form:
> (using a line break before the binary operator and nesting to the
> argument level)
> 
> write('hello %s'
>       % (world,))
> 
> 
> or optionally this form if it buys you a little more room:
> (using a hanging indent of 4 spaces and nesting arguments at that level)
> 
> write(
>     'hello %s'
>     % ('world',))
> 
> 
> but not ever this form:
> (Using a hanging indent of 4 spaces from the opening paren of the format
> operand)
> 
> write('hello %s' % (
>     'world',))
> 
> 
> 
> yea/nea?
> 
> (Kevin, Philippe, Markus, Max)

Looks good to me.

Kevin