17:24 <+cscott> i think PHP supports "property added after the fact", sort of like JS does
17:24 <+cscott> but (a) it's known to be quite slow in PHP, probably not appropriate for something used as often as data-parsoid/etc annotations
17:24 <+cscott> and (b) it *may* not be supported on native objects, which the DOM node classes might be? worth a test, maybe...
17:25 <+cscott> ...but better yet if we don't need to
17:25 <+cscott> http://php.net/manual/en/book.dom.php
17:25 <+cscott> i don't immediately see anything specific to mapping DOM nodes to native PHP objects

17:30 <+cscott> https://stackoverflow.com/questions/8707235/how-to-create-new-property-dynamically has some benchmarks

https://stackoverflow.com/questions/8707235/how-to-create-new-property-dynamically has some benchmarks showing how slow "expando" properties are.

We were mistaken about php and dynamic properties (.dataobject) on instances of classes ... so, some of the rationale for this is not valid anymore. But, from a code cleanliness POV (and performance as @cscott refers to in his comment), this may still be a good thing to do.

So it turns out that PHP's DOM classes are a bit weird. As long as a reference to the DOMNode exists in PHP, things work fine. But it seems the DOMNode object gets destroyed when the last PHP reference goes away, and a new one is then created when the same node is later accessed.

$doc = new DOMDocument;
$node = $doc->createElement( 'b' );
$node->appendChild( $doc->createElement( 'a' ) );

$a = $node->firstChild;
$a->dataobject = [];
var_dump( isset( $a->dataobject ) );                // => true
var_dump( isset( $node->firstChild->dataobject ) ); // => true

$a = null;
var_dump( isset( $node->firstChild->dataobject ) ); // => false !!
$node->firstChild->dataobject = [];
var_dump( isset( $node->firstChild->dataobject ) ); // => false !!

$a = $node->firstChild;
var_dump( isset( $node->firstChild->dataobject ) ); // => false
$node->firstChild->dataobject = [];
var_dump( isset( $node->firstChild->dataobject ) ); // => true
var_dump( isset( $a->dataobject ) );                // => true

https://gerrit.wikimedia.org/r/c/mediawiki/services/parsoid/+/487920 as well.

So, it looks like we need to implement this on the JS side first and not rely on persistence of the PHP wrapper objects around libxml2.

In T204608#4594349, @cscott wrote:

https://stackoverflow.com/questions/8707235/how-to-create-new-property-dynamically has some benchmarks showing how slow "expando" properties are.

If you're referring to https://stackoverflow.com/a/8707348/634419, that's something rather different. We're not looking at implementing __get() or __set() here. Try this:

<?php

define( 'REPS', 100000000 );

class A {
}

$t0 = microtime( true );
$a = new A();
for ( $i = 0; $i < REPS; $i++ ) {
    $a->data = 'test' . $i;
}
$t1 = microtime( true );
echo "Added property: " . ( $t1 - $t0 ) . "\n";

class B {
    public $data;
}

$t0 = microtime( true );
$b = new B();
for ( $i = 0; $i < REPS; $i++ ) {
    $b->data = 'test' . $i;
}
$t1 = microtime( true );
echo "Declared property: " . ( $t1 - $t0 ) . "\n";

On my laptop, it looks like the added property is a whole 3 or 4 nanoseconds slower.

Change 489332 had a related patch set uploaded (by Arlolra; owner: Arlolra):
[mediawiki/services/parsoid@master] [WIP] Move .dataobject off nodes

https://gerrit.wikimedia.org/r/489332

Change 489332 abandoned by Arlolra:
[WIP] Move .dataobject off nodes

https://gerrit.wikimedia.org/r/489332

In T204608#4925526, @Anomie wrote:

So it turns out that PHP's DOM classes are a bit weird. As long as a reference to the DOMNode exists in PHP, things work fine. But it seems the DOMNode object gets destroyed when the last PHP reference goes away, and a new one is then created when the same node is later accessed.

[15] boris> $doc = DOMDocument::loadHTML('<b>hi');
 → object(DOMDocument)(

)
[16] boris> $doc->env = [ 'doc' => $doc ];
 → array(
  'doc' => object(DOMDocument)(
    'env' => *** RECURSION ***
  )
)
[17] boris> $doc->lastChild->ownerDocument->env;
 → array(
  'doc' => object(DOMDocument)(
    'env' => *** RECURSION ***
  )
)
[18] boris> $n = $doc->lastChild;
 → object(DOMElement)(

)
[19] boris> $doc = null;
 → NULL
[20] boris> $n->ownerDocument->env;
 → array(
  'doc' => object(DOMDocument)(
    'env' => *** RECURSION ***
  )

Huh, the circular reference really does keep the PHP DOMDocument alive as long as a node is alive?

Change 490654 had a related patch set uploaded (by Arlolra; owner: Arlolra):
[mediawiki/services/parsoid@master] [WIP] Use a bag-on-the-side implementation for node data

https://gerrit.wikimedia.org/r/490654

Change 490654 merged by jenkins-bot:
[mediawiki/services/parsoid@master] Use a bag-on-the-side implementation for node data

https://gerrit.wikimedia.org/r/490654

Mentioned in SAL (#wikimedia-operations) [2019-02-26T18:24:33Z] <arlolra> Updated Parsoid to e82347d (T204608, T214099, T217093)