From: nobu@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:88445] [Ruby trunk Feature#14609] `Kernel#p` without args shows the receiver
Date: Sat, 11 Aug 2018 03:29:42 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-73500.20180811032940.5bbdbe667636aa20@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-14609.20180316012909@ruby-lang.org
Issue #14609 has been updated by nobu (Nobuyoshi Nakada).
osyo (manga osyo) wrote:
> Good proposal.
> This can solve the following problem.
>
> ```ruby
> # NG: syntax error, unexpected ':', expecting '}'
> p { name: "homu", age: 14 }
You can use parentheses.
```ruby
p(name: "home", age: 14)
```
----------------------------------------
Feature #14609: `Kernel#p` without args shows the receiver
https://bugs.ruby-lang.org/issues/14609#change-73500
* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 2.6
----------------------------------------
# Abstract
`Kernel#p(obj)` prints obj as `inspect`ed.
How about to show the receiver if an argument is not given?
# Background
We recently introduce `yield_self` which encourages block chain.
https://zverok.github.io/blog/2018-01-24-yield_self.html
Quoted from this article, we can write method chain with blocks:
```
construct_url
.yield_self { |url| Faraday.get(url) }.body
.yield_self { |response| JSON.parse(response) }
.dig('object', 'id')
.yield_self { |id| id || '<undefined>' }
.yield_self { |id| "server:#{id}" }
```
There is a small problem at debugging.
If we want to see the middle values in method/block chain, we need to insert `tap{|e| p e}`.
With above example,
```
construct_url
.yield_self { |url| Faraday.get(url) }.body
.yield_self { |response| JSON.parse(response) }.tap{|e| p e} # debug print
.dig('object', 'id')
.yield_self { |id| id || '<undefined>' }.tap{|e| p e} # debug print
.yield_self { |id| "server:#{id}" }
```
# Proposal
`obj.p` shows same as `p(obj)`.
We can replace
`block{...}.tap{|e| p e}`
to
`block{...}.p`
For above example, we can simply add `.p` at the end of line:
```
construct_url
.yield_self { |url| Faraday.get(url) }.body
.yield_self { |response| JSON.parse(response) }.p # debug print
.dig('object', 'id')
.yield_self { |id| id || '<undefined>' }.p # debug print
.yield_self { |id| "server:#{id}" }
```
# Compatibility issue
(1) Shorthand for `nil`
This spec change can introduce compatibility issue because `p` returns `nil` and do not output anything.
That is to say, `p` is shorthand of `nil`. Some code-golfers use it.
Maybe we can ignore them :p
(2) make public method
`Kernel#p` is private method, so if we typo `obj.x` to `obj.p` (not sure how it is feasible), it will be `NoMethodError` because of visibility.
We need to change this behavior.
# Note
## Past proposal and discussion
Endoh-san proposed same idea 10+ years ago [ruby-dev:29736] in Japanese.
I think we should revisit this idea because of `yield_self` introduction.
At this thread, Matz said "simple `p` shows `p(self)`, it is not clear".
[ruby-dev:30903]
```
p
はどう動くのかとか(p selfと同じ、は変な気が)
self.p(obj)
はどうなのかとか。その辺が解決(納得)できたら、ということで。
```
English translation:
```
What the behavior of (I feel strange that it is similar to `p(self)`):
p
What happen on
self.p(obj)
```
## pp
If this proposal is accepted, we also need to change `pp` behavior.
## gems
`tapp` method is provided by gem.
https://github.com/esminc/tapp
I'd thought to propose this method into core. But I found that `p` is more shorter than `tapp`.
Disadvantage is `p` is too short and difficult to grep.
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2018-08-11 3:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-14609.20180316012909@ruby-lang.org>
2018-03-16 1:29 ` [ruby-core:86152] [Ruby trunk Feature#14609] `Kernel#p` without args shows the receiver ko1
2018-03-16 3:11 ` [ruby-core:86153] " mame
2018-03-16 8:00 ` [ruby-core:86155] " zverok.offline
2018-03-16 10:55 ` [ruby-core:86156] " hanmac
2018-08-10 7:03 ` [ruby-core:88426] " ko1
2018-08-10 13:09 ` [ruby-core:88438] " hanmac
2018-08-11 1:49 ` [ruby-core:88444] " manga.osyo
2018-08-11 3:29 ` nobu [this message]
2018-08-18 17:59 ` [ruby-core:88546] " shevegen
2018-09-13 6:04 ` [ruby-core:88971] " nobu
2018-09-13 6:16 ` [ruby-core:88973] " matz
2018-10-13 13:57 ` [ruby-core:89400] " lukas
2018-10-16 11:13 ` [ruby-core:89416] " zverok.offline
2018-10-16 13:10 ` [ruby-core:89419] " nobu
2018-10-16 13:18 ` [ruby-core:89420] " zverok.offline
2018-10-17 16:21 ` [ruby-core:89449] " ko1
2019-03-11 4:50 ` [ruby-core:91744] " akr
2019-03-11 4:54 ` [ruby-core:91745] " nobu
2019-03-11 4:59 ` [ruby-core:91746] " ko1
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