Hi Daniel,

"When an object is cloned, PHP 5 will perform a shallow copy of all of the object's properties. Any properties that are references to other variables, will remain references."

http://php.net/manual/en/language.oop5.cloning.php

You might have look creating a "clone" in the following manner:

$clone = unserialize( serialize( $parser ) );

I'm not saying that's the best solution, but it's a quick and dirty solution that sometimes does what you need (namely a deep copy).

Cheers, Rob.

On 13-06-18 02:17 PM, Daniel Renfro wrote:

Recently I encountered what I thought was a bug in my code, but it turned out to be something much more interesting.

First, some background: Here at Vistaprint we have a number of custom extensions written for our internal-documentation wiki. One of those categorizes articles programmatically - you call it from the code and it will auto-categorize the page. Something along the effect of: $c = new Categorizer; $c->addToCategory( 'my-message-key' );

Whenever this code was called it broke the Cite extension. Specifically, anything defined with <ref></ref> would not show up in the <references /> section below. Doing some digging I found this issue:

1.   Our custom extension parsed a message in the middle of a page (while the page was being parsed in the code)
   
   

2.   Parsing a message called MessageCache::parse, by way of wfMessage() and the Message object
   
   

3.   The MessageCache object clones the global parser and parses the message
   
   

4.   Parsing the message means that the (cloned) parser calls Parser::clearState
   
   

The problem is that calling Parser::clearState() on the cloned parser object (a property of MessageCache) also clears the state of the global parser object. This might be due to two things:

1.   PHP makes shallow-copies of objects when cloning and not deep-copies [1].
   
   

2.   When the Cite extension inserts itself into a parser it sets up a callback to the 'ParserClearState' hook. When this callback is run, because of #1 (no deep-copying) it effectively gets run for all clones of the parser.
   
   

This is arguably a bug in MediaWiki: cloning a parser does not create a totally separate object with its own state. I have found a number of bug-reports that seem to be related to this issue [2][3][4]. Before I go off and submit a bunch of code, I'd like the input from the community.

Thoughts? -Daniel ( User:DanielRenfro )

References: [1] http://php.net/manual/en/language.oop5.cloning.php [2] https://bugzilla.wikimedia.org/show_bug.cgi?id=34589 [3] https://bugzilla.wikimedia.org/show_bug.cgi?id=32368 [4] https://bugzilla.wikimedia.org/show_bug.cgi?id=47291

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