From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-2.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, RCVD_IN_SBL_CSS,SPF_HELO_NONE,SPF_PASS shortcircuit=no autolearn=no autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id E7AB61F463 for ; Thu, 12 Sep 2019 15:40:43 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 14868120997; Fri, 13 Sep 2019 00:40:36 +0900 (JST) Received: from o1678948x4.outbound-mail.sendgrid.net (o1678948x4.outbound-mail.sendgrid.net [167.89.48.4]) by neon.ruby-lang.org (Postfix) with ESMTPS id 773111208F1 for ; Fri, 13 Sep 2019 00:40:34 +0900 (JST) Received: by filter0151p3mdw1.sendgrid.net with SMTP id filter0151p3mdw1-5401-5D7A66F4-2C 2019-09-12 15:40:36.438260744 +0000 UTC m=+164752.112685170 Received: from herokuapp.com (unknown [54.242.45.138]) by ismtpd0023p1iad2.sendgrid.net (SG) with ESMTP id a9zsWGdvRjSHkTioLywEqA for ; Thu, 12 Sep 2019 15:40:36.237 +0000 (UTC) Date: Thu, 12 Sep 2019 15:40:36 +0000 (UTC) From: merch-redmine@jeremyevans.net Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 70477 X-Redmine-Project: ruby-trunk X-Redmine-Issue-Id: 16157 X-Redmine-Issue-Author: Dan0042 X-Redmine-Sender: jeremyevans0 X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?RVE3t853K5scBhbmJHUzZTFFeVC=2FZSUmHZ0Dc+26wcEi2CTgsF1oz0wTSSxGGN?= =?us-ascii?Q?BIweYaMweJkVqaGco4c77slW79RuPu1tstYw38P?= =?us-ascii?Q?8gokX66vZomjpkY+qu=2Fdp=2FuddrsqIQmZEdZ1eB8?= =?us-ascii?Q?8xoQ58mV1e8JYvN8ekXZZvbGnUEhQMi1Wiwy4xM?= =?us-ascii?Q?63yKMgjqp08SPBjIdUBNRIrFBKSIiBy8m=2Fg=3D=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 94923 Subject: [ruby-core:94923] [Ruby master Misc#16157] What is the correct and *portable* way to do generic delegation? X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #16157 has been updated by jeremyevans0 (Jeremy Evans). Dan0042 (Daniel DeLorme) wrote: > After some more thinking I believe the `pass_keywords` behavior would be appropriate for 100% of methods with an argument splat but no keywords. We do not want this as the default behavior. Consider: ```ruby def foo(*args) bar(*quux) baz(*args) end ``` Here in the call to `bar`, the purpose is not to pass arguments through, but to call the method `quux` and splat the arguments received from that method as positional arguments. If `bar` accepts a positional argument splat and keyword arguments, and `quux` returns an array where the last element is a hash, then the last element will be treated as keywords to `bar`, even though that is not what we want (these are the types of bugs keyword argument separation is designed to fix). `pass_keywords` is designed only for arbitrary delegation methods, and only where backwards compatibility with Ruby <2.7 is desired. It should eventually be removed after Ruby <2.7 is EOL. As the implementation is based on VM frame flags, it requires extra internal work in the VM for every method call. ---------------------------------------- Misc #16157: What is the correct and *portable* way to do generic delegation? https://bugs.ruby-lang.org/issues/16157#change-81538 * Author: Dan0042 (Daniel DeLorme) * Status: Open * Priority: Normal * Assignee: ---------------------------------------- With the keyword argument changes in 2.7 we must now specify keyword arguments explicitly when doing generic delegation. But this change is not compatible with 2.6, where it adds an empty hash to the argument list of methods that do not need/accept keyword arguments. To illustrate the problem: ```ruby class ProxyWithoutKW < BasicObject def initialize(target) @target = target end def method_missing(*a, &b) @target.send(*a, &b) end end class ProxyWithKW < BasicObject def initialize(target) @target = target end def method_missing(*a, **o, &b) @target.send(*a, **o, &b) end end class Test def args(*a) a end def arg(a) a end def opts(**o) o end end # 2.6 2.7 3.0 ProxyWithoutKW.new(Test.new).args(42) # [42] [42] [42] ok ProxyWithoutKW.new(Test.new).arg(42) # 42 42 42 ok ProxyWithoutKW.new(Test.new).opts(k: 42) # {:k=>42} {:k=>42} +warn [{:k=>42}] incompatible with >= 2.7 ProxyWithKW.new(Test.new).args(42) # [42, {}] [42] [42] incompatible with <= 2.6 ProxyWithKW.new(Test.new).arg(42) # error 42 42 incompatible with <= 2.6 ProxyWithKW.new(Test.new).opts(k: 42) # {:k=>42} {:k=>42} +warn {:k=>42} must ignore warning? cannot use pass_positional_hash in 2.6 ``` I don't know how to solve this, so I'm asking for the **official** correct way to write portable delegation code. And by **portable** I mean code that can be used in gems that target ruby 2.6 and above. -- https://bugs.ruby-lang.org/