Open Radar

 
Summary:
When setting the anchor point on an SKSpriteNode (and presumably other nodes as well) that has a negative scale, the node will move more than one would expect from the new anchor point value, and it will also un-flip to a positive scale

Steps to Reproduce:
Minimal spriteKit project below. the 'ExpectedBehaviour.gif' file attached is what happens when the nodes scale is 0.5, 'ActualBehaviour.gif' is what happens when the nodes scale is -0.5. 

-(void)didMoveToView:(SKView *)view {
    SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithImageNamed:@"Spaceship"];
    sprite.position = CGPointMake(500, 500);
    sprite.scale = //-0.5 for broken case //0.5 for expected case
    [self addChild:sprite];
    self.ship = sprite;

}

-(void)mouseDown:(NSEvent *)theEvent {
    self.ship.anchorPoint = CGPointMake(self.ship.anchorPoint.x + 0.01f, self.ship.anchorPoint.y);
}

Expected Results:
When the node has a negative scale, I would expect it to operate just like the node in ExpectedBehaviour.gif, except mirrored

Actual Results:
Instead the node visibly flips and moves large distances that are disproportionate to the change in the anchor point

Version:
8.1.3 (12B466)

Notes:
I've noted this as an iOS issue but I am seeing the exact same outcome in the MacOS version of SpriteKit

Configuration:
iPhone 6 128GB

Attachments:
ExpectedBehaviour - https://dl.dropboxusercontent.com/s/nebzn4z5v1hh8eu/CEB7A2E7-0B17-41CB-B73B-6C58BD60A8B2-5890-000025F865CD65EF.gif?dl=0
Broken Behaviour - https://dl.dropboxusercontent.com/s/psymiho4y2wi543/34B7E358-BDA5-44FA-8F57-52DFBC665ED2-5890-00002615619AD36E.gif?dl=0