Re: [RFC][Proposal] Renamed parameters

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  111190
July 26, 2020 13:52 t.carnage@gmail.com (Chris Riley)
Hi all,

Thanks for the feedback so far. In light of the feedback received both here
and privately, I've made 3 changes to the RFC document:

1. The original option 1, allowing renaming parameters but not requiring an
explicit opt in to enable them to be called by name has been dropped. The
proposal is now only for explicit opt in parameters with renaming as a
possibility. The reasoning for this, is that although I included option 1
as I thought it might be more likely to be accepted; many people pointed
out that we are very close to the cutoff date for PHP 8.0 and that
implementing such a change would likely be too big to get done in time.
Option 1 would be possible to include in PHP 8.1 as it doesn't break BC,
this means that the proposal can be brought back targeting 8.1 should
option 2 not be accepted.

2. With respect to the feature freeze date, I've added a possible strategy
to deal with a staged implementation, should the release managers not feel
comfortable including the full feature at this late stage.

3. I have documented the main objections to the RFC on the RFC itself and
included my rebuttals; should anyone feel I've not represented their point
fairly let me know and I'll update.

Regards,
Chris

On Fri, 24 Jul 2020 at 12:12, Chris Riley carnage@gmail.com> wrote:

> Hi all, > > The named parameters RFC has been accepted, despite significant objections > from maintainers of larger OSS projects due to the overhead it adds to > maintaining backwards compatibility as it has now made method/function > parameter names part of the API; a change to them would cause a BC break > for any library users who decide to use the new feature. > > It is likely that the way this will shake out is that some maintainers > will accept the additional overhead of including parameter names in their > BC guidelines and others will not, this leaves users unsure if they can use > the new feature without storing up issues in potentially minor/security > releases of the libraries they use. This is not really an ideal situation. > > More pressing a point is that the current implementation breaks object > polymorphism. Consider this example (simplified from one of my codebases) > > interface Handler { > public function handle($message); > } > > class RegistrationHandler implements Handler { > public function handle($registraionCommand); > } > > class ForgottenPasswordHandler implements Handler { > public function handle($forgottenPasswordCommand); > } > > class MessageBus { > //... > public function addHandler(string $message, Handler $handler) { //... } > public function getHandler(string $messageType): Handler { //... } > public function dispatch($message) > { > $this->getHandler(get_class($message))->handle(message: $message); > } > } > > This code breaks at run time. > > Proposals were made for resolutions to this issue however all of them > require trade offs and could potentially break existing code. > > My proposal to resolve these two issues is to add the ability to rename > parameters with a new syntax as follows. > > function callBar(Foo $internalName:externalName) { > $internalName->bar(); > } > > $x = new Foo(); > callBar(externalName: $x); > > This allows both the above problems to be resolved, by renaming the > internal parameter and keeping the external signature the same. > > I propose that the RFC would have two voting options. > > The first would be to implement it as proposed above, this would allow any > parameter to be called by name regardless of the intentions of the author > of the method/function and is closest to the current behaviour. > > The second option would be to use this syntax to make named parameters in > userland code explicitly opt in. As such an additional shortcut syntax > would be implemented: $: to designate a named parameter. eg > > function callBar($:externalName) { > $externalName->bar(); > } > > $x = new Foo(); > callBar(externalName: $x); > > If a parameter is not opted in, a compile time error is raised: > > function callBar($externalName) { > $externalName->bar(); > } > > $x = new Foo(); > callBar(externalName: $x); // Error: cannot call parameter $externalName > by name. > > There are pros and cons to this second approach, on the one hand it > reduces the usefulness of the named parameter syntax by requiring changes > to old code to enable it (although this could probably be automated fairly > easily) however it does provide a neater solution to the second problem in > that, to prevent the runtime errors in the second issue example, every > child class would need to use the rename syntax on it's parameter to > prevent errors, whereas if we went down this route, the parent class could > just not opt into the named parameter syntax and the code would function as > expected. > > Another advantage is that with the ability to rename parameters using the > opt in, we gain some flexibility to tighten up the LSP rules relating to > named parameter inheritance. > > class Foo { > public function bar($:param) { //... } > public function baz($internal:external) { //... } > } > > // OK > class Bar { > public function bar($renamed:param) { //... } > public function baz($renamed:external) { //... } > } > > // Compile time error cannot rename named parameter $:param (renamed to > $:renamedParam) > class Baz { > public function bar($:renamedParam) { //... } > } > > // Compile time error cannot rename named parameter $:external (renamed to > $:renamed) > class Baz { > public function baz($internal:renamed) { //... } > } > > While this would be technically possible with the first option (no opt in) > it would break any existing code which renames a parameter as every > parameter would be subject to these rules. > > I don't have Wiki karma so can't post this yet; but I want to get the ball > rolling on discussion as feature freeze is coming up fast and if we want to > go for the second option, that must hit before the named parameter syntax > is in a tagged version of PHP. > > Regards, > Chris >
  111192
July 26, 2020 16:37 tysonandre775@hotmail.com (tyson andre)
Hi Chris Riley,

I agree with Rowan Tommin's arguments in https://externals.io/message/111161#111179 - I wanted named parameters by default.

Miscellaneous comments:

1. https://wiki.php.net/rfc/renamed_parameters should be moved to "In Discussion" on https://wiki.php.net/rfc/
2. I think that the RFC title should really mention "Making named parameters opt-in",
   since that part of the RFC has the largest impact.
   (e.g. "Renamed parameters and making named parameters opt-in").
   (The RFC URL should not be changed)
3. For your examples, I assume you mean "Class Bar extends Foo {" instead of "class Bar {"
4. "Error: cannot call parameter $externalName by name." seems incorrect,
    I assume "cannot call callBar() with parameter $externalName by name" or something along those lines was intended
5. https://wiki.php.net/rfc/renamed_parameters#attributes still mentions "option 1" and "option 2", but those were removed from the current version of the proposal, making this confusing
6. How will this RFC expect internal functions such as substr_compare() or internal methods such as `ArrayObject::__construct()` included in php-src?

   What about PECLs - will existing function declaration macros be treated as opted out of or into named parameters?
7. This is missing some details on how reflection and backtrace generation will be affected.
   I assume `ReflectionParameter->getInternalName(): string`, `ReflectionParameter->getExternalName(): ?string`, etc. will need to be added.
   getTrace() and getTraceAsString()
8. Renaming parameters offers only a small performance benefit and I don't think it would get used very frequently.
    It's possible to add `$newName = $oldName; unset($oldName);` (or in most cases, to update the method implementation body).
9. Are declarations such as `function test($:publicName, $nonPublicName) {}` an error?

   I'd personally prefer https://wiki.php.net/rfc/named_params#positional-only_and_named-only_parameters to allow API designers to explicitly opt out of named parameters.
10. As Rowin Tommins had said, "maintainers of larger OSS projects" is a broad claim and could be clarified
   (e.g. what fraction of maintainers? Were there polls/discussion threads of maintainers/owners of OSS projects?)

Since there are strong objections from some maintainers of supporting always-enabled named parameters,
I'd think a useful alternative would be to add a positional-only parameter syntax instead in 8.0, similar to what Python,
so that maintainers that want to avoid supporting named parameters in their API can clearly express that in a release requiring ^8.0.
This is using syntax for https://www.python.org/dev/peps/pep-0570/#history-of-positional-only-parameter-semantics-in-python for clarity,
but obviously other syntax might suit PHP better.
(mentioned in https://wiki.php.net/rfc/named_params#positional-only_and_named-only_parameters)

```
function test(int $x, /, string $y) {}
test(x: 1, y: "test");  // Error: test() does not support being called with parameter $x by name
test(1, y: "test");  // allowed
function test_varargs(...$args, /) {}
test_varargs(x: 1);  // Error: test_varargs() does not support being called with named variable argument $x in ...$args
test_varargs(...['x' => 1]);  // Error: test_varargs() does not support being called with named variable argument $x in ...$args
```

There may be concerns such as whether `/` can be added when overriding,
or in forbidding using `...$newArgs, /` to override `...$originalArgs`
but since parameter renaming was already allowed in the Named Arguments RFC this should not be a new issue.

Regards,
- Tyson
  111193
July 26, 2020 16:42 kontakt@beberlei.de (Benjamin Eberlei)
On Sun, Jul 26, 2020 at 3:52 PM Chris Riley carnage@gmail.com> wrote:

> Hi all, > > Thanks for the feedback so far. In light of the feedback received both here > and privately, I've made 3 changes to the RFC document: > > 1. The original option 1, allowing renaming parameters but not requiring an > explicit opt in to enable them to be called by name has been dropped. The > proposal is now only for explicit opt in parameters with renaming as a > possibility. The reasoning for this, is that although I included option 1 > as I thought it might be more likely to be accepted; many people pointed > out that we are very close to the cutoff date for PHP 8.0 and that > implementing such a change would likely be too big to get done in time. > Option 1 would be possible to include in PHP 8.1 as it doesn't break BC, > this means that the proposal can be brought back targeting 8.1 should > option 2 not be accepted >
Can you clarify if opt-in would only be the behavior on userland functions, or if all internal functions would also change to opt-in? If no, then the inconsistency must be explained. if yes then the next steps for each internal API to decide on allowing named params or not needs to be explained Both approaches lead to a lot of problems down the road that were nicely circumvented by auto-optin of all functions. Implementation wise, with external name, you have only one name on the call site. That means if you decide to rename an argument, then you cannot support both the old and the new name for one major release cycle to allow your users to upgrade smoothly. As such it is my opinion that this is an inferior approach to having an alias that allows declaring a second name. Have you given an E_NOTICE/E_WARNING a thought? A user of a library could then overwrite a library authors "with" to disallow named parameters. Can you add an example how the MessageHandler problem would look like with your proposal? Is the external name inherited? Is it forced to inherit? Can it be overwritten?
> 2. With respect to the feature freeze date, I've added a possible strategy > to deal with a staged implementation, should the release managers not feel > comfortable including the full feature at this late stage. >
Can you update the Proposed Voting Choices section with the two questions for the staged implementation? or the one question combining them both? The wording is going to be signifcant for further discussion.
> 3. I have documented the main objections to the RFC on the RFC itself and > included my rebuttals; should anyone feel I've not represented their point > fairly let me know and I'll update. >
Your "objections" section mentions the inheritance / polymorphism part being buried/hidden in the RFC, but its a section on its own https://wiki.php.net/rfc/named_params#parameter_name_changes_during_inheritance and Nikita sent several mails to the list about this topic, asking for specific feedback about this outstanding issue alone. The main change in your RFC from explicitly enabled for all userland and internal functions to an opt-in approach for userland functions was also discussed in depth. Similar approaches to your suggestions were also mentioned again in the RFC prominently under "Alternatives", overruled by the voted upon implementation that got 76% acceptance.
> > Regards, > Chris >
At this point I would much prefer to discuss amendments within the current behavior and not against it. My counter-proposal is still to have two, potentially three attributes: - @@NameAlias to define a second name/alias for a parameter. Would help solve both polymorphic name changes and refactoring of names. - @@PositionalArgumentsOnly to define on a function or class, throwing an exception if used with named arguments. This only slightly makes the use case of named arguments slower. Maybe the reverse with @@NamedArgumentsOnly - however checking for that would probably slightly make all positional calls slower, which will probably stay the primary way of calling functions. Trade offs are unclear here. I know attributes "feel" wrong here, being a new feature and not been used for anything yet in the language. But attributes have the benefit of not introducing new keywords or syntax to the language and are the right tool to "re-configure" a feature from its primary behavior. Use of attributes would also keep open future changes (by introducing new attributes or arguments to the existing ones) leaving our options open instead of locking them down further.
> On Fri, 24 Jul 2020 at 12:12, Chris Riley carnage@gmail.com> wrote: > > > Hi all, > > > > The named parameters RFC has been accepted, despite significant > objections > > from maintainers of larger OSS projects due to the overhead it adds to > > maintaining backwards compatibility as it has now made method/function > > parameter names part of the API; a change to them would cause a BC break > > for any library users who decide to use the new feature. > > > > It is likely that the way this will shake out is that some maintainers > > will accept the additional overhead of including parameter names in their > > BC guidelines and others will not, this leaves users unsure if they can > use > > the new feature without storing up issues in potentially minor/security > > releases of the libraries they use. This is not really an ideal > situation. > > > > More pressing a point is that the current implementation breaks object > > polymorphism. Consider this example (simplified from one of my codebases) > > > > interface Handler { > > public function handle($message); > > } > > > > class RegistrationHandler implements Handler { > > public function handle($registraionCommand); > > } > > > > class ForgottenPasswordHandler implements Handler { > > public function handle($forgottenPasswordCommand); > > } > > > > class MessageBus { > > //... > > public function addHandler(string $message, Handler $handler) { > //... } > > public function getHandler(string $messageType): Handler { //... } > > public function dispatch($message) > > { > > $this->getHandler(get_class($message))->handle(message: > $message); > > } > > } > > > > This code breaks at run time. > > > > Proposals were made for resolutions to this issue however all of them > > require trade offs and could potentially break existing code. > > > > My proposal to resolve these two issues is to add the ability to rename > > parameters with a new syntax as follows. > > > > function callBar(Foo $internalName:externalName) { > > $internalName->bar(); > > } > > > > $x = new Foo(); > > callBar(externalName: $x); > > > > This allows both the above problems to be resolved, by renaming the > > internal parameter and keeping the external signature the same. > > > > I propose that the RFC would have two voting options. > > > > The first would be to implement it as proposed above, this would allow > any > > parameter to be called by name regardless of the intentions of the author > > of the method/function and is closest to the current behaviour. > > > > The second option would be to use this syntax to make named parameters in > > userland code explicitly opt in. As such an additional shortcut syntax > > would be implemented: $: to designate a named parameter. eg > > > > function callBar($:externalName) { > > $externalName->bar(); > > } > > > > $x = new Foo(); > > callBar(externalName: $x); > > > > If a parameter is not opted in, a compile time error is raised: > > > > function callBar($externalName) { > > $externalName->bar(); > > } > > > > $x = new Foo(); > > callBar(externalName: $x); // Error: cannot call parameter $externalName > > by name. > > > > There are pros and cons to this second approach, on the one hand it > > reduces the usefulness of the named parameter syntax by requiring changes > > to old code to enable it (although this could probably be automated > fairly > > easily) however it does provide a neater solution to the second problem > in > > that, to prevent the runtime errors in the second issue example, every > > child class would need to use the rename syntax on it's parameter to > > prevent errors, whereas if we went down this route, the parent class > could > > just not opt into the named parameter syntax and the code would function > as > > expected. > > > > Another advantage is that with the ability to rename parameters using the > > opt in, we gain some flexibility to tighten up the LSP rules relating to > > named parameter inheritance. > > > > class Foo { > > public function bar($:param) { //... } > > public function baz($internal:external) { //... } > > } > > > > // OK > > class Bar { > > public function bar($renamed:param) { //... } > > public function baz($renamed:external) { //... } > > } > > > > // Compile time error cannot rename named parameter $:param (renamed to > > $:renamedParam) > > class Baz { > > public function bar($:renamedParam) { //... } > > } > > > > // Compile time error cannot rename named parameter $:external (renamed > to > > $:renamed) > > class Baz { > > public function baz($internal:renamed) { //... } > > } > > > > While this would be technically possible with the first option (no opt > in) > > it would break any existing code which renames a parameter as every > > parameter would be subject to these rules. > > > > I don't have Wiki karma so can't post this yet; but I want to get the > ball > > rolling on discussion as feature freeze is coming up fast and if we want > to > > go for the second option, that must hit before the named parameter syntax > > is in a tagged version of PHP. > > > > Regards, > > Chris > > >
  111195
July 26, 2020 18:32 rowan.collins@gmail.com (Rowan Tommins)
Hi Chris,


On 26/07/2020 14:52, Chris Riley wrote:
> Thanks for the feedback so far. In light of the feedback received both here > and privately, I've made 3 changes to the RFC document
Firstly, a reminder of the guideline in the RFC howto that the link to the RFC should be included in replies, which is particularly relevant when announcing changes to the text. For others trying to find it, it is here: https://wiki.php.net/rfc/renamed_parameters Secondly, regardless of the merits of your proposal in itself, I think an RFC in this position should explicitly state why it is proposing to re-visit an accepted feature. I can think of a handful of possible reasons, but none seem to apply: - If new concerns have come to light which are likely to change the opinion of those who voted Yes. This is not the case for the concerns in your introduction. - If the RFC passed only by a narrow margin, or a low turnout, and this version is expected to gain a larger majority. The RFC passed with a ratio of 3:1, with 75 votes cast [1]. - If the RFC discussion was rushed, so that people did not have adequate time to understand the proposal and discuss its implications. The RFC was informally resurrected at the start of April [2] and formally at the start of May [3] and saw plenty of discussion. - If there is evidence that people voted Yes despite reservations that this proposal resolves. No evidence is presented of this, and the only message of that sort in the voting thread expressed reservations unrelated to this proposal. [4] - If there is evidence that (a significant number of) people who voted Yes have now changed their minds having re-considered the implications. No evidence is presented of this. As Benjamin says, the pragmatic way forward would be to discuss enhancements on top of the accepted feature, rather than last-minute alternatives to it. [1] This appears to be the second highest turnout after Scalar Type Declarations, according to https://php-rfc-watch.beberlei.de/ [2] https://externals.io/message/109549 [3] https://externals.io/message/110004 [4] https://externals.io/message/110910#110961 Regards, -- Rowan Tommins (né Collins) [IMSoP]
  111207
July 28, 2020 04:33 tysonandre775@hotmail.com (tyson andre)
Hi internals,

Continuing on my response in https://externals.io/message/111161#111192 , and considering ways to enhance named arguments without a BC break
(while minimizing the impact on application/library authors that wish for their libraries not to be used with named parameters)

I was considering setting up a short straw poll on the wiki for a week with two questions, open for a week:

1. Whether voters consider it appropriate to add amendments/enhancements to named parameters (in general) in php 8.0 past the feature freeze. (Both/Backward Compatible Enhancements Only/No)
   (yes if interested in any of the alternatives proposed in https://externals.io/message/111161)

   I'd recognize that named parameters are potentially a large change to what is considered the public API of a project,
   so I'd think continuing to add enhancements would be worthwhile, but I'd like to know where others stand on this.
   (e.g. if any proposals I made should be postponed to 8.1)

   I'd also think that implementing a backwards incompatible change after the feature freeze (in terms of impact on code targeting 8.0 alphas at the time of the feature freeze)
    would be a bad precedent.

2. Interest in adding support for positional-only arguments in 8.0 or 8.1 (3 options: 8.0, 8.1, or no)

   (e.g. with a symbol such as `/` to indicate that parameters or variadic parameters prior to the symbol are positional-only)

   I'd consider positional-only arguments useful in some cases, such as where the names would always be confusing,
   (or automatically generated code)

   - `function my_merge(string $firstArg, ...string $otherArgs, /) { }`
     This also provides an easy way for user-defined code to add restrictions similar to what `array_merge()` already has.
   - `function my_pow($x, $y, $z = null, /,) {}`
   - `function autoGeneratedCode($arg1, $arg2, /) {}

   Other syntaxes are possible, such as using attributes
   (I would find 5 attributes rather verbose if there were 5 positional-only parameters),
   or keywords such as `__END_POSITIONAL_PARAMETERS`.
   Nothing stood out as a good option (e.g. `_`, `...`, `%` seem meaningless, `*` would be the opposite of python, `#` can't be used),
   and I've only seen markers for the end of positional-only parameters in python after a quick check, so at least some users would find `/` easier to learn/remember.

--------

On an unrelated note,

1. A few people had suggested adding a line to a README indicating that named parameters aren't supported.
An idea I had was to standardize on a machine-readable file format (e.g. ".php_analysis_config.json") that IDEs/analyzers may choose to support.
It might have JSON entries such as `"supports_named_parameters": false` to indicate that code (e.g. src/main.php) using files in that directory (e.g. vendor/a/b/ with vendor/a/b/.php_analysis_config.json)
should not invoke functions/methods in vendor/a/b/ with named parameters,
because there is no guarantee the names will remain the same.
(TOML or ini settings might be more readable, but a complicated format requires extra dependencies and ini files won't support arrays if future settings get added)

- I can't think of many other settings I'd want there that aren't covered by composer.json, editorconfig, or other means.
  Maybe less importantly `"supports_classes_being_extended": bool`
- Alternately, it might be possible to put it in "extra" of composer.json,
  but some projects/libraries don't use composer.json (e.g. a project has both vendor/ and third-party/)
- I'm not aware of similar indicators for python for named arguments, so there might not be much interest in such a proposal. Then again, I think python had named arguments for much longer.

2. Another attribute idea I had was `<>` on a class/method,
to make PHP enforce that method overrides other than __construct must
have the same names in the same positions and not lead to errors when valid named arguments are passed to subclasses,
but I don't plan to propose that any earlier than 8.1
(e.g. for classes that have calls such as `$this->method(someFlag: true);`)

Thanks,
- Tyson