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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