[#100309] How to use backport custom field — Jun Aruga <jaruga@...>
Please allow my ignorance.
9 messages
2020/10/06
[#100310] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/06
IkJhY2twb3J0IGN1c3RvbSBmaWVsZCIgaXMgb25seSBhdmFpbGFibGUgZm9yIHRpY2tldHMgd2hv
[#100311] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/06
On Tue, Oct 6, 2020 at 4:44 PM NARUSE, Yui <[email protected]> wrote:
[#100314] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/06
VGhhbmsgeW91IGZvciBjb25maXJtYXRpb24uCkkgY2hlY2tlZCBhZ2FpbiBhbmQgdG8gZWRpdCBi
[#100322] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/07
On Tue, Oct 6, 2020 at 7:25 PM NARUSE, Yui <[email protected]> wrote:
[#100326] Re: How to use backport custom field
— "NARUSE, Yui" <naruse@...>
2020/10/07
SSBhZGRlZCB5b3UgdG8gIlJlcG9ydGVyIiByb2xlIGluIHRoZSBwcm9qZWN0CgoyMDIw5bm0MTDm
[#100327] Re: How to use backport custom field
— Jun Aruga <jaruga@...>
2020/10/07
On Wed, Oct 7, 2020 at 1:42 PM NARUSE, Yui <[email protected]> wrote:
[ruby-core:100502] [Ruby master Feature#16461] Proc#using
Issue #16461 has been updated by Dan0042 (Daniel DeLorme).
Eregon (Benoit Daloze) wrote in #note-10:
> Maybe a way to design this restriction could be to annotate the method `where` with "enables MyRefinement on the lexical block given to it".
I like this idea. Since the block should always have the same refinements, it makes sense to define them once rather than every time the block is called. How about
```ruby
class ModelClassMethods
using ActiveRecord::WhereDSL, def where(&block)
...
block.call / yield
end
end
```
----------------------------------------
Feature #16461: Proc#using
https://bugs.ruby-lang.org/issues/16461#change-88122
* Author: shugo (Shugo Maeda)
* Status: Assigned
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 3.0
----------------------------------------
## Overview
I propose Proc#using to support block-level refinements.
```ruby
module IntegerDivExt
refine Integer do
def /(other)
quo(other)
end
end
end
def instance_eval_with_integer_div_ext(obj, &block)
block.using(IntegerDivExt) # using IntegerDivExt in the block represented by the Proc object
obj.instance_eval(&block)
end
# necessary where blocks are defined (not where Proc#using is called)
using Proc::Refinements
p 1 / 2 #=> 0
instance_eval_with_integer_div_ext(1) do
p self / 2 #=> (1/2)
end
p 1 / 2 #=> 0
```
## PoC implementation
For CRuby: https://github.com/shugo/ruby/pull/2
For JRuby: https://github.com/shugo/jruby/pull/1
## Background
I proposed [Feature #12086: using: option for instance_eval etc.](https://bugs.ruby-lang.org/issues/12086) before, but it has problems:
* Thread safety: The same block can be invoked with different refinements in multiple threads, so it's hard to implement method caching.
* _exec family support: {instance,class,module}_exec cannot be supported.
* Implicit use of refinements: every blocks can be used with refinements, so there was implementation difficulty in JRuby and it has usability issue in headius's opinion.
## Solutions in this proposal
### Thread safety
Proc#using affects the block represented by the Proc object, neither the specific Proc object nor the specific block invocation.
Method calls in a block are resolved with refinements which are used by Proc#using in the block at the time.
Once all possible refinements are used in the block, there is no need to invalidate method cache anymore.
See [these tests](https://github.com/shugo/ruby/pull/2/commits/1c922614ad7d1fb43b73e195348c81da7a4546ef) to understand how it works.
Which refinements are used is depending on the order of Proc#using invocations until all Proc#using calls are finished, but eventually method calls in a block are resolved with the same refinements.
### * _exec family support
[Feature #12086](https://bugs.ruby-lang.org/issues/12086) was an extension of _eval family, so it cannot be used with _exec family, but Proc#using is independent from _eval family, and can be used with _exec family:
```ruby
def instance_exec_with_integer_div_ext(obj, *args, &block)
block.using(IntegerDivExt)
obj.instance_exec(*args, &block)
end
using Proc::Refinements
p 1 / 2 #=> 0
instance_exec_with_integer_div_ext(1, 2) do |other|
p self / other #=> (1/2)
end
p 1 / 2 #=> 0
```
### Implicit use of refinements
Proc#using can be used only if `using Proc::Refinements` is called in the scope of the block represented by the Proc object.
Otherwise, a RuntimeError is raised.
There are two reasons:
* JRuby creates a special CallSite for refinements at compile-time only when `using` is called at the scope.
* When reading programs, it may help understanding behavior. IMHO, it may be unnecessary if libraries which uses Proc#using are well documented.
`Proc::Refinements` is a dummy module, and has no actual refinements.
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