From: eregontp@gmail.com
To: ruby-core@ruby-lang.org
Subject: [ruby-core:96855] [Ruby master Feature#15357] Proc#parameters returns incomplete type information
Date: Tue, 14 Jan 2020 13:21:35 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-83865.20200114132135.aee73f27e13223ba@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-15357.20181128200114@ruby-lang.org
Issue #15357 has been updated by Eregon (Benoit Daloze).
I agree, and discussed that a bit in #16499.
I think Proc#parameters should expose source-level information, not interpret it according to Kernel#lambda?.
----------------------------------------
Feature #15357: Proc#parameters returns incomplete type information
https://bugs.ruby-lang.org/issues/15357#change-83865
* Author: larskanis (Lars Kanis)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
----------------------------------------
The current implementation of Proc#parameters [differentiate between lambda? true and false](https://github.com/ruby/ruby/blob/49cd16bfaf4f03885058ce748119bc8ea2de735a/iseq.c#L2800).
This is presumably due to the fact, that [procs use tricks](https://ruby-doc.org/core-2.5.3/Proc.html#method-i-parameters) to apply arguments differently than lambda and methods.
Unfortunately `proc{}.parameters` states all `:req` parameters as `:opt`, so that these both types of parameters are not distinguishable. This information loss leads to the situation that two different proc signatures return an equal parameters list, but behave differently:
```ruby
pr = proc{|a,b=2| [a,b] }
pr.parameters # => [[:opt, :a], [:opt, :b]]
pr.call(:a) # => [:a, 2] # :a is interpret as the first parameter
pr = proc{|a=1,b| [a,b] }
pr.parameters # => [[:opt, :a], [:opt, :b]]
pr.call(:a) # => [1, :a] # :a is interpret as the second parameter
```
That means that the current return values of `proc{}.parameters` are not suitable to build wrapper or proxy objects for a proc. In Eventbox a workaround is used: The proc is passed to `define_method` and the [method parameters are retrieved instead](https://github.com/larskanis/eventbox/blob/3bcbc30096c6003e96d41c6496c781dfc90ac36a/lib/eventbox/argument_wrapper.rb#L10-L17). That way the list of parameters can be retrieved including `:req` and `:opt` differentiation, so that a wrapper proc can be built.
The application of argument assignment tricks is a property of the Proc object - not a property of single parameters. Therefore it shouldn't be applied to `Proc#parameters` in addition - at least not in a way that discards valuable information. The property of the Proc object is already readable through `Proc#lambda?`, so that there's no need to apply this property to `Proc#parameters` as well.
My proposal is to unify `proc{}.parameters` and `lambda{}.parameters`, so that `proc{}.parameters` shows positional arguments without default value as type `:req` as well.
---Files--------------------------------
proc-parameters-req-15357.patch (5.15 KB)
--
https://bugs.ruby-lang.org/
prev parent reply other threads:[~2020-01-14 13:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-15357.20181128200114@ruby-lang.org>
2018-11-28 20:01 ` [ruby-core:90135] [Ruby trunk Bug#15357] Unify proc{} and lambda{}.parameters lars
2019-08-28 2:12 ` [ruby-core:94625] [Ruby master Feature#15357] Proc#parameters returns incomplete type information merch-redmine
2020-01-14 10:11 ` [ruby-core:96846] " lars
2020-01-14 13:21 ` eregontp [this message]
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