fix: Ensure schedule.steps is always incremented before data collection

[rht]

This replaces #92.

[EwoutH]

Could you describe the problem and why this solution fixed it, for clarity?

[rht]

The problem is when trade is disabled, the steps never get incremented because the code exits early in this code branch. Needs a manual self.schedule.steps += 1, because there is no self.schedule.step() call. The trading Sugarscape needs custom scheduling that is beyond staged activation, and is more easily expressed by the AgentSet API.

[EwoutH]

Would this work? If so, I think it's more elegant:

def step(self):
    """
    Unique step function that does staged activation of sugar and spice
    and then randomly activates traders
    """
    # Step Resource agents
    for resource in self.schedule.agents_by_type[Resource]:
        resource.step()

    # Step trader agents
    trader_shuffle = self.randomize_traders()
    for agent in trader_shuffle:
        agent.prices = []
        agent.trade_partners = []
        agent.move()
        agent.eat()
        agent.maybe_die()

    if self.enable_trade:
        # If trade is enabled, shuffle and proceed with trading
        trader_shuffle = self.randomize_traders()
        for agent in trader_shuffle:
            agent.trade_with_neighbors()

    # Update step count and collect data
    self.schedule.steps += 1
    self.datacollector.collect(self)

[rht]

No it doesn't, because there are more lines of code beyond self.datacollector.collect(self) when trade is enabled:

mesa-examples/examples/sugarscape_g1mt/sugarscape_g1mt/model.py

Lines 188 to 205 in cf38477

	"""
	Mesa is working on updating datacollector agent reporter
	so it can collect information on specific agents from
	mesa.time.RandomActivationByType.
	Please see issue #1419 at
	https://github.com/projectmesa/mesa/issues/1419
	(contributions welcome)
	Below is one way to update agent_records to get specific Trader agent data
	"""
	# Need to remove excess data
	# Create local variable to store trade data
	agent_trades = self.datacollector._agent_records[self.schedule.steps]
	# Get rid of all None to reduce data storage needs
	agent_trades = [agent for agent in agent_trades if agent[2] is not None]
	# Reassign the dictionary value with lean trade data
	self.datacollector._agent_records[self.schedule.steps] = agent_trades

.

[rht]

We can optimize the code clarity later. This PR's scope is to fix the test issue with a very localized patch.

[EwoutH]

Indeed, this PR fixes the issue. We can refactor later.