Newsgroups: php.internals Path: news.php.net Xref: news.php.net php.internals:110111 Return-Path: Delivered-To: mailing list internals@lists.php.net Received: (qmail 11761 invoked from network); 10 May 2020 18:56:10 -0000 Received: from unknown (HELO php-smtp4.php.net) (45.112.84.5) by pb1.pair.com with SMTP; 10 May 2020 18:56:10 -0000 Received: from php-smtp4.php.net (localhost [127.0.0.1]) by php-smtp4.php.net (Postfix) with ESMTP id 2964E1804C4 for ; Sun, 10 May 2020 10:32:24 -0700 (PDT) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on php-smtp4.php.net X-Spam-Level: X-Spam-Status: No, score=-1.6 required=5.0 tests=BAYES_00,KHOP_HELO_FCRDNS, SPF_HELO_NONE,SPF_NONE autolearn=no autolearn_force=no version=3.4.2 X-Spam-ASN: AS24940 88.99.0.0/16 X-Spam-Virus: No X-Envelope-From: Received: from mail.netwake.de (srv2.netwake.de [88.99.170.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by php-smtp4.php.net (Postfix) with ESMTPS for ; Sun, 10 May 2020 10:32:23 -0700 (PDT) Received: from M-DE-010.fritz.box (unknown [IPv6:2a04:4540:1604:2800:5b9:fdfd:a776:1f7d]) (Authenticated sender: thomas.lamy@netwake.de) by mail.netwake.de (Postfix) with ESMTPSA id CDEA826BF54 for ; Sun, 10 May 2020 19:32:21 +0200 (CEST) To: internals@lists.php.net References: Message-ID: <5317ed17-1ea0-0cc7-18bb-d5c4a1ea8354@netwake.de> Date: Sun, 10 May 2020 19:32:21 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Subject: Re: [PHP-DEV] Proposal For Return-If / Early Return / Guard Clause Syntax From: thomas.lamy@netwake.de (Thomas Lamy) Am 10.05.20 um 18:26 schrieb John Bafford: > Hi Ralph, > >> On May 10, 2020, at 11:49, Ralph Schindler wrote: >> >> Hi! >> >> >> # Intro >> >> I am proposing what is a near completely syntactical addition (only change is to language.y) to the language. The best terminology for this syntax is are: `return if`, "return early", or "guard clauses". >> >> see: https://en.wikipedia.org/wiki/Guard_(computer_science) >> >> Over the past few years, I've seen a growing number of blog posts, conference talks, and even tooling (for example code complexity scoring), that suggest writing guard clauses is a good practice to utilize. I've also seen it more prevalent in code, and even attempts at achieving this with Exceptions (in an HTTP context) in a framework like Laravel. >> >> see abort_if/throw_if: https://laravel.com/docs/7.x/helpers#method-abort-if >> >> It is also worth mentioning that Ruby has similar features, and I believe they are heavily utilized: >> >> see: https://github.com/rubocop-hq/ruby-style-guide#no-nested-conditionals >> >> >> # Proposal >> >> In an effort to make it a first class feature of the language, and to make the control flow / guard clauses more visible when scanning code, I am proposing this in the syntax of adding `return if`. >> >> The chosen syntax is: >> >> return if ( if_expr ) [: optional_return_expression] ; >> >> As a contrived example: >> >> function divide($dividend, $divisor = null) { >> return if ($divisor === null || $divisor === 0); >> >> return $dividend / $divisor; >> } >> >> There is already a little discussion around the choice of order in the above statement, the main take-aways and (my) perceived benefits are: >> >> - it keeps the intent nearest the left rail of the code (in normal/common-ish coding standards) >> >> - it treats "return if" as a meta-keyword; if must follow return for the statement to be a guard clause. This also allows a person to more easily discern "returns" from "return ifs" more easily since there is not an arbitrary amount of code between them (for example if the return expression were after return but before if). >> >> - it has the quality that optional parts are towards the end >> >> - is also has the quality that the : return_expression; is very symmetrical to the way we demarcate the return type in method signatures >> "): return type {" for example. >> >> - has the quality of promoting single-line conditional returns >> >> >> # Finally >> >> One might say this is unnecessary syntactic sugar, which is definitely arguable. But we do have multiple ways of achieving this. >> >> Of course all of these things should be discussed, I think sub-votes (should this PR make it that far) could be considered. >> >> The PR is located here: >> >> https://github.com/php/php-src/pull/5552 >> >> As mentioned, some discussion is happening there as well. >> >> >> Thanks! >> Ralph Schindler >> >> >> PS: since implementing the ::class feature 8 years ago, the addition of the AST abstraction made this kind of syntactical change proof-of-concept so much easier, bravo! > I'm in favor of language features that encourage defensive coding, so, I think the concept behind return-if is good, but your approach too limited. > > I think a more general guard syntax would be better: > > guard (some condition) else { > //code here must exit the parent block, or else an error is generated (at compile-time if possible) > } > > This would allow for more and broader use cases: the code in the else clause could do any of return, continue, break, throw, exit, or maybe even goto, as appropriate to the condition and its parent block, which could be any functional block — a function, loop, if, else, try, or catch clause, or the "global" scope outside of a function or class definition. And, if you did return (as opposed to something else), you'd retain locality of 'return' and the return value, rather than separating it with the condition. > > -John > Hi all, In contrast, I really like Ralph's proposal for it's simplicity. I would prefer a single keyword, though.