Calling reset() on Sprite with a P2 body can result in body.data.world == null

[jonkelling]

Steps:

1. When a Sprite with a Phaser.Physics.P2.Body has exists set to false--e.g. on kill()--the body is QUEUED to be REMOVED.
2. The Sprite is now available via getFirstExists(false), for example, and may have reset() called at this time. Calling reset() will set exists = true, which effectively ADDs the body to the world WITHOUT the QUEUE.
3. The Sprite has health, it exists, is visible, etc. etc., but a split-second later, P2 processes the _toRemove queue and removed the body from the world.
4. Your Sprite appears dead in the water. Or in space. Or whatever. (humor implied)

Proposed solution: In physics/p2/World.js, the addBody function should remove the body from the _toRemove queue.

[jonkelling]

Sorry, that solution didn't work. This one did, though:

Added the following code to the beginning of the Phaser.Physics.P2.Body#addToWorld method:

        if (this.game.physics.p2._toRemove)
            for (var i = 0; i < this.game.physics.p2._toRemove.length; i++)
                if (this.game.physics.p2._toRemove[i] === this)
                    this.game.physics.p2._toRemove.splice(i, 1);

So, it looks like this:

    /**
    * Adds this physics body to the world.
    *
    * @method Phaser.Physics.P2.Body#addToWorld
    */
    addToWorld: function () {

        if (this.game.physics.p2._toRemove)
            for (var i = 0; i < this.game.physics.p2._toRemove.length; i++)
                if (this.game.physics.p2._toRemove[i] === this)
                    this.game.physics.p2._toRemove.splice(i, 1);

        if (this.data.world !== this.game.physics.p2.world)
        {
            this.game.physics.p2.addBody(this);
        }

    },

[jonkelling]

I understand I may have submitted this impatiently and that the solution may not be in the best place. It does appear solve the problem, though, and I will try to get back to it when I can. Thanks.

[jonkelling]

This code demonstrates the problem. Notice I use setInterval and setTimeout instead of game.time.events.loop. Using the game.....loop functionality, the problem does not occur, but if your trigger is a key press or mouse click, it does. The setInterval/setTimeout operates pretty much to the same effect as using a key press, but you don't have to mash buttons to recreate it. So...notice there are three bullets that fire. After 5 seconds, the first bullet shot disappears and a new one SHOULD fire; however, it just appears and looks stuck, as described in this issue.

var game = new Phaser.Game(800, 600, Phaser.AUTO, 'issue917', { preload: preload, create: create, update: update });

var bulletGroup;
var canFire = true;

function preload()
{
    game.load.image('bullet', 'bullet.png');
}

function create()
{
    game.physics.startSystem(Phaser.Physics.P2JS);

    bulletGroup = game.add.group();
    bulletGroup.enableBody = true;
    bulletGroup.physicsBodyType = Phaser.Physics.P2;
    bulletGroup.createMultiple(3, 'bullet');
    bulletGroup.forEach(function(bullet) {
        game.physics.p2.enable(bullet);
    })

    setInterval(fireNext, 0);
}

function update()
{

}

function fireNext()
{
    if (canFire)
    {
        setTimeout(function() { canFire = true; }, 1000);
        canFire = false;
        var nextBullet = bulletGroup.getFirstExists(false);
        if (nextBullet)
        {
            nextBullet.reset(game.width / 2, game.height - 50);
            nextBullet.body.moveForward(100);
            nextBullet.lifespan = 5000;
        }
    }
}

[photonstorm]

Merged into dev, thank you :)