rfc:trailing-commas-function-calls

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rfc:trailing-commas-function-calls [2017/10/07 18:17] – created sammykrfc:trailing-commas-function-calls [2017/10/07 18:21] (current) – Delete sammyk
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-====== PHP RFC: Allow trailing commas in function calls ====== +Oops! Wrong URL - sorry! I don't know how to delete.
-  * Version: 0.1 +
-  * Date: 2017-10-06 +
-  * Author: Sammy Kaye Powers, me@sammyk.me +
-  * Status: Under Discussion +
-  * First Published at: https://wiki.php.net/rfc/list-syntax-trailing-commas (2017-01-27) & https://wiki.php.net/rfc/trailing-comma-function-args (2013-02-19) +
- +
-===== Introduction ===== +
-Allowing a trailing comma in function calls will make it more convenient to append arguments in many contexts where it is common to call a function with lots of arguments; especially variadic functions. +
- +
-===== Proposal ===== +
-Trailing commas have been allowed in array syntax since forever-ever, and in grouped namespace syntax since PHP 7.2. +
- +
-<code php> +
-# Currently possible +
-use Foo\Bar\{ +
-    Foo, +
-    Bar, +
-}; +
- +
-$foo = [ +
-    'foo', +
-    'bar', +
-]; +
-</code> +
- +
-Allowing a trailing comma makes sense in these contexts as new values get appended frequently. There is another context wherein appending more values frequently happens: calling a variadic function. +
- +
-<code php> +
-unset( +
-    $foo, +
-    $bar, +
-    $baz, +
-); +
-</code> +
- +
-===== Frequent Context Examples ===== +
-Trailing commas in function calls make it crazy convient to invoke any function that takes variable arguments (i.e. using the splat operator <php>...</php> or <php>func_get_args()</php>.) +
- +
-==== Unsetting variables ==== +
-It is extremely common to send a list of two or more arguments to <php>unset()</php> to unset variables. +
- +
-<code php> +
-unset( +
-    $somethingIDontNeedAnymore, +
-    $anotherOneToKill, +
-    $letsMakeThisEasy, +
-); +
-</code> +
- +
-==== Sending variables to a template engine ==== +
-Another extremely common practice is to send a list of variables to a tempalte engine concisely using <php>compact()</php>. +
- +
-<code php> +
-echo $twig->render( +
-    'index.html', +
-    compact( +
-        'title', +
-        'body', +
-        'comments', +
-    ) +
-); +
-</code> +
- +
-==== Merging arrays ==== +
-Invoking <php>array_merge()</php> is another great example of how trailing commas make values easier to append. +
- +
-<code php> +
-$newArray = array_merge( +
-    $arrayOne, +
-    $arrayTwo, +
-    ['foo', 'bar'], +
-); +
-</code> +
- +
-==== Debugging all the things ==== +
-When you're quickly debugging with <php>var_dump()</php>, it's nice to not have to worry about removing that dangling comma in order for your script to run. +
- +
-<code php> +
-var_dump( +
-    $whatIsInThere, +
-    $probablyABugInThisOne, +
-    $oneMoreToCheck, +
-); +
-</code> +
- +
-==== i18n & l10n ==== +
-Internationalization & localization often makes use of variadic functions such as <php>sprintf()</php> that usually expand and contract over time. +
- +
-<code php> +
-$en = 'Trailing %s makes %s a happy developer.'; +
-$text = sprintf( +
-    $en, +
-    'commas', +
-    'Jane', +
-); +
-</code> +
- +
-==== And so on... ==== +
-This list of examples is not meant to be exhaustive, but you can see how allowing a trailing comma in function calls fits well within the existing trailing comma contexts (arrays & grouped namespaces). +
- +
-===== Method & closure calls too ===== +
-Method calls also adopt trailing comma functionality. +
- +
-<code php> +
-class Foo +
-{ +
-  public function __construct(...$args) { +
-    // +
-  } +
-   +
-  public function bar(...$args) { +
-    // +
-  } +
-   +
-  public function __invoke(...$args) { +
-    // +
-  } +
-} +
- +
-$foo = new Foo( +
-  'constructor', +
-  'bar', +
-); +
- +
-$foo->bar( +
-  'method', +
-  'bar', +
-); +
- +
-$foo( +
-  'invoke', +
-  'bar', +
-); +
-</code> +
- +
-And closures too. +
- +
-<code php> +
-$bar = function(...$args) { +
-  // +
-}; +
- +
-$bar( +
-  'closure', +
-  'bar', +
-); +
-</code> +
- +
-===== "Not really a function" functions as well ===== +
-There are two language constructs that look like functions but aren't that will also allow trailing commas: <php>unset()</php> (as mentioned before) and <php>isset()</php>. +
- +
-<code php> +
-unset($foo, $bar,); +
-var_dump(isset($foo, $bar,)); +
-</code> +
- +
-===== Wait, didn't we just vote on this? ===== +
-Yes, there was an RFC to [[https://wiki.php.net/rfc/list-syntax-trailing-commas|add trailing commas to all list syntax in PHP 7.2]]. Unfortunately due to an oversight on my end, the vote for function calls and function declarations was combined into one vote so the vote failed (but just barely!) +
- +
-I was contacted by many "no" voters saying that they would have voted "yes" for function calls, but "no" for function declarations. This RFC proposes allowing a trailing comma in function call syntax only. +
- +
-We are allowed to put this feature up for vote again since the mandatory 6-month waiting period has passed since the last vote and this RFC targets a new major version of PHP. +
- +
-===== Backward Incompatible Changes ===== +
-None +
- +
-===== Proposed PHP Version(s) ===== +
-PHP 7.3 +
- +
-===== What's not allowed ===== +
-Function declaration syntax will not change. This RFC targets function call syntax only. +
- +
-<code php> +
-# Parse error +
-function bar($a, $b,) { +
-    // +
-} +
-</code> +
- +
-Free-standing commas are not allowed. +
- +
-<code php> +
-# Parse error +
-foo(,); +
-</code> +
- +
-Multiple trailing commas & leading commas are not allowed. +
- +
-<code php> +
-# Parse error +
-foo('function', 'bar',,); +
-# Also parse error +
-foo(, 'function', 'bar'); +
-</code> +
- +
-Other things that could look like functions like <php>yield</php> & <php>list()</php> will go untouched and no other list syntax will be affected. +
- +
-===== Proposed Voting Choices ===== +
-Requires a 2/3 or 50%+1 majority +
- +
-===== Patches and Tests ===== +
-This patch, sans the tests, is a trivial three-line change in the parser. +
- +
-[[https://github.com/SammyK/php-src/compare/master...rfc-trailing-comma-function-calls|See the diff on GitHub]] +
- +
-The trailing comma is thrown out at the parser level so there's no runtime computations wasted. +
- +
-===== Implementation ===== +
-After the project is implemented, this section should contain  +
-  - the version(s) it was merged to +
-  - a link to the git commit(s) +
-  - a link to the PHP manual entry for the feature +
-  - a link to the language specification section (if any) +
-  +
rfc/trailing-commas-function-calls.1507400253.txt.gz · Last modified: 2017/10/07 18:17 by sammyk

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