bug#60186: 29.0.60; ruby-mode indentation of multi-line expressions

[Dmitry Gutov <dgutov@yandex.ru>]

On 20/12/2022 06:48, Aaron Jensen wrote:

> In all seriousness though,
> 
>>> Current:
>>>
>>> some_variable = some_object.
>>>                     some_method
>>>
>>> Desired:
>>>
>>> some_variable = some_object.
>>>     some_method
> 
> This one isn't quite right, maybe there was an email formatting issue.
> I'm expecting some_method to be indented by 1 level, for me it's 2:
> 
> some_variable = some_object.
>      some_method

Yes, that's also the "needs more work" part.

>>>
>>> Current:
>>>
>>> some_variable = some_number + some_other_number *
>>>                                 some_third_number + some_fourth_number -
>>>                   some_fifth_number
>>>
>>> Desired:
>>>
>>> some_variable = some_number + some_other_number *
>>>     some_third_number + some_fourth_number -
>>>     some_fifth_number
> 
> This looks good.

The funny thing is this case looked more difficult originally.

>> This will take some more work too. Not in the least because the
>> "Desired" forms looks illogical (at least in the context of SMIE): we're
>> already "escaping" the current syntax node to line the indentation of
>> the block to the beginning of the statement (which makes sense, at least
>> from the ergonomics POV), so why would the line break matter?
> 
> Do you mean why are these different?
> 
> some_variable = some_array.
>    map do |x|
>      x + 1
>    end
> 
> vs
> 
> some_variable = some_array.map do |x|
>    x + 1
> end
> 
> It's because the end is lined up with the line opened the
> block/increased indentation. In the first example, the indented map
> line is the beginning and on the second, it's the assignment.

One might ask why it's lined up to 'map' only after it's moved to the 
next line, but not in the first example.

Anyway, the important part is to choose an unambiguous algorithm, even 
if it uses its own logic.

>> Take more complex cases. How much indentation will the block have after
>> some heterogeneous continuations? Is this right?
>>
>>     some_variable = 4 +
>>       some_array.
>>         reduce do |acc, x|
>>           acc + x
>>         end
> 
> No, there is nothing that would cause reduce to be further indented.
> It should be this:
> 
> some_variable = 4 +
>    some_array.
>    reduce do |acc, x|
>      acc + x
>    end

Okay, so there should be two basic cases:

- Indent to the beginning of the statement,
- If there was a line continuation (no matter how many), indent 1 extra 
level?

And maybe something related to parentheses, if used.