Profiling reveals that >87% of the run time of our test suite is spent
in this tiny method. Apparently, DOMNodeList::item() is extremely slow
(possibly it's linear time instead of constant time?).
Profiled using XDebug and KCacheGrind:
https://phabricator.wikimedia.org/F31815264
We can calculate the child's index in its parent by counting its
precending siblings instead, which turns out to be much faster.
Before:
1. 275444ms to run DiscussionToolsCommentParserTest:testGetComments with data set #2
2. 12668ms to run DiscussionToolsCommentParserTest:testGetComments with data set #3
...
After:
1. 9545ms to run DiscussionToolsCommentParserTest:testGetComments with data set #2
2. 5549ms to run DiscussionToolsCommentParserTest:testGetComments with data set #3
...
That's still kind of slow but now it's bearable to run the test suite.
Change-Id: I49155f7aa2e231a9a20bf282cf6aaa28fc902e0b
* Not to be confused with the Parsing Team's
"Great Parser JS to PHP port of 2019"
Gasp as OR hacks are changed to null coalescing operators.
Applaud as variable declarations are dropped.
Cheer as parameters and return values are type-hinted.
Shudder as DomNodeLists have no indexOf method.
Moving discussion parsing to the server should allow
us to implement much cleaner APIs for commenting.
Bug: T252252
Co-authored-by: Ed Sanders <esanders@wikimedia.org>
Change-Id: Ic1438d516e223db462cb227f6668e856672f538c
