rfc:stringable

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
rfc:stringable [2020/01/22 15:20]
nicolasgrekas
rfc:stringable [2020/08/01 23:38] (current)
carusogabriel RFC was implemented
Line 2: Line 2:
   * Version: 0.9   * Version: 0.9
   * Date: 2020-01-15   * Date: 2020-01-15
-  * Author: Nicolas Grekas, nicolas.grekas+php@gmail.com +  * Author: Nicolas Grekas, nicolasgrekas@php.net 
-  * Status: Draft+  * Status: Implemented
   * First Published at: http://wiki.php.net/rfc/stringable   * First Published at: http://wiki.php.net/rfc/stringable
  
 ===== Introduction ===== ===== Introduction =====
-This PR introduces a new ''Stringable'' interface that can be added to classes that implement the ''%%__toString()%%'' method.+ 
 +This RFC introduces a new ''Stringable'' interface that is automatically added to classes that implement the ''%%__toString()%%'' method. 
 It has two goals: It has two goals:
-  - allow using ''string|Stringable'' to express ''string | object-with-%%__toString()%%''+  - allow using ''string|Stringable'' to express ''string|object-with-%%__toString()%%''
   - provide a forward upgrade path from PHP 7 to 8   - provide a forward upgrade path from PHP 7 to 8
  
 ===== Proposal ===== ===== Proposal =====
-Goal 1. is to allow using the ''string|Stringable'' union type in PHP 8, to accept both strings and objects that implement ''%%__toString()%%'' //and// declare this interface. This is critically missing currently, on codes that deal with stringable objects: they can't be made type-safe.+Goal 1. is to allow using the ''string|Stringable'' union type in PHP 8, to accept both strings and objects that implement ''%%__toString()%%''. This is critically missing currently, on codes that deal with stringable objects: they can't be made type-safe.
  
-Classes that implement ''%%__toString()%%'' aren'required to declare the interface as that would prevent seamless forward/backward compatibility with PHP 7.+Classes that implement ''%%__toString()%%'' can also declare the interface explicitly. Classes that don't declare the interface explicitly will still declare it implicitly. This allows both forward compatibility and backward compatibility: using a polyfill, classes can declare the interface on PHP 7; and on PHP 8, classes that don't do so will still be compatible with the ''string|Stringable'' union type.
  
-By being simple and without any magic capabilities on its own, this interface is trivially polyfilled on PHP < 8. +Once a polyfill becomes widely available (e.g. [[https://github.com/symfony/polyfill/pull/224|as part of symfony/polyfill-php80]]), code style checkers could be able to enforce declaring the interface when ''%%__toString()%%'' is declared explicitlyfor people that prefer doing so.
- +
-Once a polyfill becomes widely available (e.g. as part of symfony/polyfill-php80), we can expect code style checkers to be able to enforce declaring the interface when ''%%__toString()%%'' is used. For projects that don't use cs checkersthey'll notice quickly that they missed adding the interface because their users will ask for it when they'll want to pass the ''string|Stringable'' union type.+
  
 Here is the stub declaration of the interface: Here is the stub declaration of the interface:
Line 32: Line 32:
 Because it adds the ''string'' return type, this interface has the potential to force a BC break on any existing libraries that want to adopt it. Because it adds the ''string'' return type, this interface has the potential to force a BC break on any existing libraries that want to adopt it.
  
-In order to ease forward and backward compatibility, the PR also adds the return type to existing ''%%__toString()%%'' methods when it's not explicitly declared already. Returning a string is already enforced by the engine so this doesn't change any semantics.+In order to ease forward and backward compatibility, this RFC also proposes to automatically add the return type at compile time when a ''%%__toString()%%'' method doesn't do it explicitly already. Returning a string is already enforced by the engine so this doesn't change any semantics.
  
 This way, code moving to PHP8 won't be forced to add the return type explicitly (which would break BC on their side), and code in PHP < 8 can adopt a polyfill interface immediately (one that doesn't declare the return type for the same BC reasons.) This way, code moving to PHP8 won't be forced to add the return type explicitly (which would break BC on their side), and code in PHP < 8 can adopt a polyfill interface immediately (one that doesn't declare the return type for the same BC reasons.)
  
-Providing an easy forward-path is the second goal of this PR.+Providing an easy forward-path is the second goal of this RFC.
  
-For reference, [[https://github.com/symfony/symfony/search?q=%22%40param+string%7Cobject%22+stringable&unscoped_q=%22%40param+string%7Cobject%22+stringable|here are some annotations in Symfony]], added by contributions from real-world use cases and that currently cannot be expressed precisely enough using any union types in PHP 8.+For reference, [[https://github.com/symfony/symfony/search?q=%22%40param+string%7Cstringable%22|here are some annotations in Symfony]], added by contributions from real-world use cases and that currently cannot be expressed precisely enough using any union types in PHP 8.
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
Line 48: Line 48:
 ===== RFC Impact ===== ===== RFC Impact =====
 ==== To Existing Extensions ==== ==== To Existing Extensions ====
-Extensions will need to add the ''string'' return type when they declare ''%%__toString()%%'' methods.+Extensions will need to declare both the interface and the ''string'' return type when they declare ''%%__toString()%%'' methods if they want to pass the ''string|Stringable'' union type.
  
 ===== Open Issues ===== ===== Open Issues =====
-Make sure there are no open issues when the vote starts!+none
  
 ===== Unaffected PHP Functionality ===== ===== Unaffected PHP Functionality =====
-Declaring this interface is not required to benefit from the magic of the ''%%__toString()%%'' method.+Declaring this interface is not mandatory to benefit from the magic of the ''%%__toString()%%'' method.
  
 ===== Future Scope ===== ===== Future Scope =====
-none+void
  
 ===== Proposed Voting Choices ===== ===== Proposed Voting Choices =====
-Accept the proposed interface for PHP 8.0: yes/no+yes/no 
 + 
 +===== Vote ===== 
 +<doodle title="Adopt the Stringable interface as proposed in this RFC?" auth="nicolasgrekas" voteType="single" closed="true"> 
 +   * Yes 
 +   * No 
 +</doodle>
  
 ===== Patches and Tests ===== ===== Patches and Tests =====
Line 77: Line 83:
 ===== Rejected Features ===== ===== Rejected Features =====
  
- - Adding a new ''%%stringable%%'' special type (like ''iterable'', ''callable'', etc.) is not considered in this RFC because it would require adding a new reserved keyword in the language. This would break BC more heavily and would defeat goal #2 mentioned previously (ability to polyfill on PHP7.) +  - Adding a new ''%%stringable%%'' special type (like ''iterable'', ''callable'', etc.) is not considered in this RFC because it would require adding a new reserved keyword in the language. This would break BC more heavily and would defeat goal #2 mentioned previously (ability to polyfill on PHP7.) 
- - Consistently, this RFC doesn't embed any ''%%is_stringable()%%'' function. If we were to consider one, defining what happens when e.g. an int is passed [[https://externals.io/message/98424|has no simple answers]]. +  - Consistently, this RFC doesn't embed any ''%%is_stringable()%%'' function. If we were to consider one, defining what happens when e.g. an int is passed [[https://externals.io/message/98424|has no simple answers]]. 
- - it has been proposed [[https://github.com/php/php-src/pull/5083#issuecomment-573899924|on the GitHub PR]] that the method attached to the interface could be named ''%%toString()%%'' instead of ''%%__toString()%%''. This idea goes further than strictly required to achieve goal #1 and has been objected as not necessary in the following comments. For reference, [[https://github.com/php/php-src/pull/5088|here is a naive implementation]] of the proposal. What the patch highlights is that this increases the complexity of the engine, for a reason that would need to be justified.+  - it has been proposed [[https://github.com/php/php-src/pull/5083#issuecomment-573899924|on the GitHub PR]] that the method attached to the interface could be named ''%%toString()%%'' instead of ''%%__toString()%%''. This idea goes further than strictly required to achieve goal #1 and has been objected as not necessary in the following comments. For reference, [[https://github.com/php/php-src/pull/5088|here is a naive implementation]] of the proposal. What the patch highlights is that this increases the complexity of the engine, for a reason that would need to be justified.
rfc/stringable.1579706440.txt.gz · Last modified: 2020/01/22 15:20 by nicolasgrekas