DateTime range include? returns wrong output (or so I think)

[apneadiving]

Steps to reproduce

ref = DateTime.now
ts1 = (ref - 1.hour)..(ref + 1.hour)
ts2 = (ref)..(ref + 1.hour)
ts1.include? ts2.first
> false

Expected behavior

ts1.include? ts2.first should return true

Actual behavior

ts1.include? ts2.first returns false

Side notes

Interestingly enough, if you use Time instead of DateTime, it works as expected.

With Ruby only, it does not work...

require 'date'
ref = DateTime.now
ts1 = (ref - Rational(3600, 86400))..(ref + Rational(3600, 86400))
ts2 = (ref)..(ref + Rational(3600, 86400))
ts1.include? ts2.first
> false

System configuration

Rails version: 5.1.3
Ruby version: 2.4.2

[nicolasblanco]

On your use case Range#include? does not return what you expect simply because a range of two DateTimes is not converted to an array containing all the dates with a granularity of a second.

You need to use Range#cover? to check if a value is between your range of two DateTimes.

[apneadiving]

cover? works but... the whole point is to do something like: ts1.include?(ts2).

ActiveSupport extends include? properly to check range to range. Internally it checks: ts1.include?(ts2.first) && ts1.last >= ts2.last.

So it fails because of the ts1.include?(ts2.first)...

What is also confusing is that it works with Time but not DateTime.

[nicolasblanco]

@apneadiving : have a look at:
https://github.com/rails/rails/blob/v5.1.4/activesupport/lib/active_support/core_ext/range/include_range.rb

Range#include? is only extended in ActiveSupport to support a Range as a parameter. If something different than a Range is passed, the original behaviour is applied.

[apneadiving]

@nicolasblanco indeed this is what I describe :) it works fine with Time but not with DateTime.

[nicolasblanco]

@apneadiving

About your question on why you have a different behaviour between a range of DateTimes and a range of Times:

Ruby has a customized way of dealing with a range of Times. For this reason, you cannot convert a range of Times to an array:

(Time.now..3.hours.from_now).to_a
#=> TypeError: can't iterate from Time

But you can convert a range of DateTimes to an array:

(DateTime.now..(DateTime.now + 3.days)).to_a
#=> [Wed, 04 Oct 2017 16:49:43 +0200, Thu, 05 Oct 2017 16:49:43 +0200, Fri, 06 Oct 2017 
16:49:43 +0200, Sat, 07 Oct 2017 16:49:43 +0200]

As you see, when converting a range of DateTimes to an array, Ruby has a granularity of 1 day between each DateTime.

That's why you don't have the expected behaviour when using Range#include? with DateTime values...

[apneadiving]

The whole point of my issue is questionning the inconsistency of what include? returns between Time and DateTime.
Hopefuly it would be considered as a legitimate request.

[al2o3cr]

Looks like DateTime should be considered a "linear object" like Time and Numeric are in this patch:

https://bugs.ruby-lang.org/issues/11113

Since it isn't, the default include? implementation from Enumerable gets used. The default behavior of Range performs each using succ, which increments a DateTime by a full day. :(

[pixeltrix]

The issue with DateTime ranges should be fixed in Ruby itself by removing the succ method and making include? use cover? like core Ruby does for floats. However ActiveSupport::TimeWithZone does not have a succ method but include? doesn't work because the linear object check is coded to a fixed set of core types - this we can fix in Active Support.