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Date: Fri, 5 Jul 2024 18:26:40 -0400
Message-ID: <CAEUnE0dz3AL_B4xdnz-UAmHaKYDSByi1tRUJNwuyr=spM1L_wQ@mail.gmail.com>
Subject: Re: [PHP-DEV] [PHP-Dev] Versioned Packagers (Iteration IV)
To: PHP internals <internals@lists.php.net>
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From: tendoaki@gmail.com (Michael Morris)

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On Fri, Jul 5, 2024 at 2:23=E2=80=AFPM Dusk <dusk@woofle.net> wrote:

>
> To that end - consider the following. Let's say that two different files
> in your project import different versions of package Foo. Foo contains a
> definition of the FooBar class, and contains functions which return that
> object.
>
> 1) If $foobar is one of those FooBar objects, what does $foobar::class
> return?


Depends on where it was imported to.  The current system ALWAYS imports to
the root namespace. This new system can import there, but also to another
namespace.  This was outlined in my previous email.

For @A\Foo\FooBar the import will put FooBar at \A\Foo\FooBar, and that's
what class will return.  @B\Foo\FooBar will bind it to \B\Foo\FooBar and
that will be the return of the class constant within the class.



> Is it the same as the fully qualified name of FooBar (e.g. "Foo\FooBar")?
> Does the result differ depending on what file contains that code?
>

Again, it depends on which package namespace the code was imported into.
Foo\FooBar isn't a fully qualified name even in current PHP. Fully
qualified names start with \, so the fully qualified name is \Foo\FooBar
provided it was included into the root namespace.


>
> 2) What happens if you try to pass that string back to something like new
> $class() or construct a ReflectionClass for it? Does that depend on the
> location of the call? What if the call is through something like
> PDO::FETCH_CLASS which occurs within the runtime?
>

Again, which package are we in?


>
> 3) Within Foo, would it be true that if $x =3D new FooBar(), then $x::cla=
ss
> =3D=3D=3D FooBar::class?


Yes.


> Does this differ outside Foo (with an appropriately qualified name for
> FooBar)?
>

That's tricker, because the namespace matters in a way that it doesn't
matter now. Given an import mapping of "@A\FooBar" then

  namespace A;

  $x =3D new FooBar();
  $x::class =3D=3D=3D FooBar::class // true, however...
  echo $x::class //  \A\Foo\FooBar

That holds true even if FooBar's declaration file doesn't invoke any
namespace.


>
> 4) If those two files both create FooBar objects of their respective
> versions, what happens if you try to pass one of those objects to a
> function in the file using the "wrong" version of Foo? Does it pass type
> checks, and what happens if it does? If not, how does the check fail?
>

Each package has its own Foo\FooBar. They won't be interoperable even
though they arise from the same code. If they should be or need to be
interoperable then PHP will have to gain a notion of package beyond what's
been scoped out here.


> 5) What shows up in the output of functions like get_declared_classes()?
> Are there multiple instances of FooBar in there for each version? How are
> they distinguished from one another?


You'll get
\A\Foo\FooBar
\B\Foo\FooBar

If you also directly load Foo\FooBar into the root namespace using the
composer autoloader you could also see \Foo\FooBar

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Fri, Jul 5, 2024 at 2:23=E2=80=AFP=
M Dusk &lt;<a href=3D"mailto:dusk@woofle.net">dusk@woofle.net</a>&gt; wrote=
:</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;=
border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
To that end - consider the following. Let&#39;s say that two different file=
s in your project import different versions of package Foo. Foo contains a =
definition of the FooBar class, and contains functions which return that ob=
ject.<br>
<br>
1) If $foobar is one of those FooBar objects, what does $foobar::class retu=
rn? </blockquote><div><br></div><div>Depends on where it was imported to.=
=C2=A0 The current system ALWAYS imports to the root namespace. This new sy=
stem can import there, but also to another namespace.=C2=A0 This was outlin=
ed in my previous email.</div><div><br></div><div>For @A\Foo\FooBar the imp=
ort will put FooBar at \A\Foo\FooBar, and that&#39;s what class will return=
.=C2=A0=C2=A0@B\Foo\FooBar will bind it to \B\Foo\FooBar and that will be t=
he return of the class constant within the class.<br></div><div><br></div><=
div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0=
px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Is it the=
 same as the fully qualified name of FooBar (e.g. &quot;Foo\FooBar&quot;)? =
Does the result differ depending on what file contains that code?<br></bloc=
kquote><div><br></div><div>Again, it depends on which package namespace the=
 code was imported into.=C2=A0 Foo\FooBar isn&#39;t a fully qualified name =
even in current PHP. Fully qualified names start with \, so the fully quali=
fied name is \Foo\FooBar provided it was included=C2=A0into the root namesp=
ace.</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margi=
n:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex=
">
<br>
2) What happens if you try to pass that string back to something like new $=
class() or construct a ReflectionClass for it? Does that depend on the loca=
tion of the call? What if the call is through something like PDO::FETCH_CLA=
SS which occurs within the runtime?<br></blockquote><div><br></div><div>Aga=
in, which package are we in?</div><div>=C2=A0</div><blockquote class=3D"gma=
il_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,2=
04,204);padding-left:1ex">
<br>
3) Within Foo, would it be true that if $x =3D new FooBar(), then $x::class=
 =3D=3D=3D FooBar::class? </blockquote><div><br></div><div>Yes.</div><div>=
=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0=
.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Does this dif=
fer outside Foo (with an appropriately qualified name for FooBar)?<br></blo=
ckquote><div><br></div><div>That&#39;s tricker, because the namespace matte=
rs in a way that it doesn&#39;t matter now. Given an import mapping of &quo=
t;@A\FooBar&quot; then</div><div><br></div><div>=C2=A0 namespace A;</div><d=
iv>=C2=A0=C2=A0</div><div>=C2=A0 $x =3D new FooBar();</div><div>=C2=A0 $x::=
class =3D=3D=3D FooBar::class // true, however...</div><div>=C2=A0 echo $x:=
:class //=C2=A0 \A\Foo\FooBar</div><div><br></div><div>That holds true even=
 if FooBar&#39;s=C2=A0declaration file doesn&#39;t invoke any namespace.</d=
iv><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
4) If those two files both create FooBar objects of their respective versio=
ns, what happens if you try to pass one of those objects to a function in t=
he file using the &quot;wrong&quot; version of Foo? Does it pass type check=
s, and what happens if it does? If not, how does the check fail?<br></block=
quote><div><br></div><div>Each package has its own Foo\FooBar. They won&#39=
;t be interoperable even though they arise from the same code. If they shou=
ld be or need to be interoperable then PHP will have to gain a notion of pa=
ckage beyond what&#39;s been scoped out here.</div><div>=C2=A0</div><blockq=
uote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1p=
x solid rgb(204,204,204);padding-left:1ex">
5) What shows up in the output of functions like get_declared_classes()? Ar=
e there multiple instances of FooBar in there for each version? How are the=
y distinguished from one another?</blockquote><div><br></div><div>You&#39;l=
l get</div><div>\A\Foo\FooBar</div><div>\B\Foo\FooBar</div><div>=C2=A0</div=
><div>If you also directly load Foo\FooBar into the root namespace using th=
e composer autoloader you could also see \Foo\FooBar</div></div></div>

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