rfc:deprecate-implicitly-nullable-types

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rfc:deprecate-implicitly-nullable-types [2024/01/22 15:42] – Correct grammar in a few places theodorejbrfc:deprecate-implicitly-nullable-types [2024/04/11 13:02] (current) – kocsismate
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 ====== PHP RFC: Deprecate implicitly nullable parameter types ====== ====== PHP RFC: Deprecate implicitly nullable parameter types ======
  
-  * Version: 0.1+  * Version: 0.2
   * Date: 2023-12-20   * Date: 2023-12-20
   * Authors: Máté Kocsis <kocsismate@php.net>, Gina Peter Banyard <girgias@php.net>   * Authors: Máté Kocsis <kocsismate@php.net>, Gina Peter Banyard <girgias@php.net>
-  * Status: Under Discussion+  * Status: Implemented
   * Target Version: PHP 8.4   * Target Version: PHP 8.4
   * Implementation: [[https://github.com/php/php-src/pull/12959|https://github.com/php/php-src/pull/12959]]   * Implementation: [[https://github.com/php/php-src/pull/12959|https://github.com/php/php-src/pull/12959]]
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 the [[rfc:callable|callable type]] as of PHP 5.4, <php>array</php> as of PHP 5.1, and class types as of PHP 5.0. the [[rfc:callable|callable type]] as of PHP 5.4, <php>array</php> as of PHP 5.1, and class types as of PHP 5.0.
  
-As it was impossible to have a default value for such types, +As there wasn't a syntax for nullable type declarations at the time, 
-PHP 5.1 enabled using <php>null</php> (and only <php>null</php>) as a default value for these types, making them implicitly nullable.+PHP 5.1 enabled using <php>null</php> (and only <php>null</php>) as a default value for typed parameters, making them implicitly nullable.
  
 However, the implicitly nullable semantics are confusing and conflict with other language rules, However, the implicitly nullable semantics are confusing and conflict with other language rules,
-in particular because type declarations of these types can be misleading as to what types they actually accept.+in particular because such type declarations can be misleading as to what types they actually accept.
  
 Furthermore, this syntax still permits signatures such as: Furthermore, this syntax still permits signatures such as:
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 Deprecated: Implicitly marking parameter $var as nullable is deprecated, the explicit nullable type must be used instead Deprecated: Implicitly marking parameter $var as nullable is deprecated, the explicit nullable type must be used instead
 </PHP> </PHP>
 +
 +And remove support for implicitly nullable types in PHP 9.
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
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 Using an implicitly nullable type will emit a deprecation notice. Using an implicitly nullable type will emit a deprecation notice.
  
-There exist a variety of userland tools to automatically update implicit +==== Impact analysis and migration paths ==== 
-nullable types to explicit nullable types. + 
-One such example is the <php>nullable_type_declaration_for_default_null_value</php> +Out of the top 2000 composer packages 880 use implicitly nullable types. [2] 
-fixer from [[https://github.com/PHP-CS-Fixer/PHP-CS-Fixer|PHP-CS-Fixer]].+One explanation for such a high usage is that using implicitly nullable types 
 +was mandated by Symfony's coding style. 
 + 
 +However, there exist a variety of tools to automatically update code to use 
 +explicit nullable types from the <php>T $parameter = null</php> syntax to <php>?T $parameter = null</php>. 
 +And Symfony used one of them to migrate their codebase, and change their coding style, 
 +in anticipation of this RFC. [3] 
 + 
 +Two such tools are [[https://github.com/PHP-CS-Fixer/PHP-CS-Fixer|PHP-CS-Fixer]] 
 +with the <php>nullable_type_declaration_for_default_null_value</php> fixer, 
 +and [[https://github.com/PHPCSStandards/PHP_CodeSniffer/|PHP_CodeSniffer]] 
 +using the <php>SlevomatCodingStandard.TypeHints.NullableTypeForNullDefaultValue</php> sniff 
 +from the [[https://github.com/slevomat/coding-standard|Slevomat Coding Standard]]. 
 + 
 +It should be noted that it is possible to ignore the commit which fixes these issues from the 
 +<php>git blame</php> command since git version 2.23 via the <php>--ignore-rev</php> argument flag or the creation of a 
 +<php>.git-blame-ignore-revs</php> file which is passed to the <php>--ignore-revs-file</php> argument flag. 
 + 
 +This flag can also be automatically configured using: 
 +<code>shell 
 +git config blame.ignoreRevsFile .git-blame-ignore-revs 
 +</code> 
 + 
 +One other issue which might be revealed when converting implicitly nullable types to explicit ones 
 +without removing the default <php>null</php> value, is that an optional parameter might now exist before a mandatory one. 
 +Which will cause a secondary deprecation notice as this was [[https://github.com/php/php-src/pull/5067|deprecated in PHP 8.0]] as previously mentioned.
  
 As the <php>?T</php> syntax has existed since PHP 7.1, which is 7 years old, As the <php>?T</php> syntax has existed since PHP 7.1, which is 7 years old,
-we deem version cross compatibility to be a non-issue.+the various tools available to fix this issue automatically, 
 +and this issue being easily resolved as it requires a single change at the declaration site 
 +(instead of potentially infinite call-site changes), 
 +we deem this deprecation to be easily handled and fixed. 
 + 
 +==== Code change examples ==== 
 + 
 +The following example: 
 +<PHP> 
 +class Foo { 
 +    public function bar(int $x = null, float $y) { 
 +        // ... 
 +    } 
 +} 
 +</PHP> 
 + 
 +should end up looking like: 
 +<PHP> 
 +class Foo { 
 +    public function bar(?int $x, float $y) { 
 +        // ... 
 +    } 
 +} 
 +</PHP>
  
 ===== Version ===== ===== Version =====
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 As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted. As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.
  
-Voting started on 2024-XX-XX and will end on 2024-XX-XX.+Voting started on 2024-02-28 and will end on 2024-03-13.
    
 <doodle title="Accept Deprecate implicitly nullable parameter types RFC?" auth="girgias" voteType="single" closed="true"> <doodle title="Accept Deprecate implicitly nullable parameter types RFC?" auth="girgias" voteType="single" closed="true">
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 [1] https://externals.io/message/114007#114026 [1] https://externals.io/message/114007#114026
 +
 +[2] https://gist.github.com/kocsismate/cf3bdfbf35eb10224ee5ecd29b39656b
 +
 +[3] https://github.com/symfony/symfony/pull/53612
  
rfc/deprecate-implicitly-nullable-types.1705938133.txt.gz · Last modified: 2024/01/22 15:42 by theodorejb

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