ruby-core

Issue #12306 has been updated by shevegen (Robert A. Heiler).


Sam suggested the topic to be discussed at the next upcoming ruby
developer meeting here recently:

https://bugs.ruby-lang.org/issues/14861

I'll add a few comments to the issue here as a consequence.

I am mostly neutral to the whole issue at hand, though up to slightly in
disfavour of adding #blank? and respectively #present?.

It's not that I do not understand the use case; I simply don't think
the method names make a lot of sense. What is a "blank" string really?

If it is an empty string, then it should be called an empty string. But
rails also considers an empty array to be "blank", so I am confused -
see lateron in this comment.

I understand that we want to query the whitespace status via #blank? but
then why not call it #whitespace? or something similar? And why does
ActiveSupport use #blank? across several different classes with a
different meaning/behaviour - such as on arrays?

So, my problem is primarily with the name, only secondarily the
functionality in itself.

Note also that while active* is big, active* is not ruby as a whole.
For core functionality, the reasoning should be "because lots of ruby
people may need this or that" rather than "because it is used in 
active*, we should make it part of ruby", in my opinion. These two
can often be synonymous but the reasoning should still come from
a general user's perspective.

As for #present?, I have even less of an idea what this is supposed
to do. I had a look at the docu for ActiveSupport:

http://guides.rubyonrails.org/active_support_core_extensions.html#blank-questionmark-and-present-questionmark

"The method present? is equivalent to !blank?."

I think that is also weird from a design point of view.

It's a bit like .select versus .reject, except just for a (forward
or backwards) query. Would you have guessed that "#present?" is the
opposite to "#blank?"? I would not have.

"The following values are considered to be blank in a Rails application"
"  empty arrays and hashes, and"
"  any other object that responds to empty? and is empty."

Is also a weird design choice. In the latter blank? is suddenly
equivalent to .empty? for general objects - but we already have
that method name for e. g. Strings. So I don't think this is a
good design decision that Rails did, but that is my opinion and
I am sure many rails people think it's a great design decision.

It's good that ruby is that flexible though.

As for #strip handling unicode, if it is possible I think it would
be nice. People could then assume that calling .strip on a unicode
string would remove e. g. newlines and whitespace on the ends/sides.

I don't know how difficult it would be to have this; guess Martin
Dürst knows more here. Do all languages support this behaviour
by the way? Perhaps some languages have no whitespace, like
some symbols-based languages perhaps.

----------------------------------------
Feature #12306: Implement String #blank? #present? and improve #strip and family to handle unicode
https://bugs.ruby-lang.org/issues/12306#change-72948

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
----------------------------------------
Time and again there have been rejected feature requests to Ruby core to implement `blank` and `present` protocols across all objects as ActiveSupport does. I am fine with this call and think it is fair. 

However, for the narrow case of String having `#blank?` and `#present?` makes sense. 

- Provides a natural extension over `#strip`, `#lstrip` and `#rstrip`. `("   ".strip.length == 0) == "    ".blank?`

- Plays nicely with ActiveSupport, providing an efficient implementation in Ruby core: see: https://github.com/SamSaffron/fast_blank, implementing blank efficiently requires a c extension. 

However, if this work is to be done, `#strip` and should probably start dealing with unicode blanks, eg: 

```
irb(main):008:0> [0x3000].pack("U")
=> "　"
irb(main):009:0> [0x3000].pack("U").strip.length
=> 1
```

So there are 2 questions / feature requests here

1. Can we add blank? and present? to String? 
2. Can we amend strip and family to account for unicode per: https://github.com/SamSaffron/fast_blank/blob/master/ext/fast_blank/fast_blank.c#L43-L74



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