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Actions After Start

Once you call the start_server() function, no other code will run until your website finishes.

from drafter import *

# These print statements demonstrate when code runs relative to start
print("This line will execute before the game starts.")
start_server()
print("This line will not execute until the game is over."

If you want to have activity in your website, you have to use the route decorator to add routes.

Circular Reference Errors

Drafter does its best to automatically generate unit tests for your code. However, it is not perfect. One particular issue is if you have a circular reference in your data. The unit test will seem to randomly have the text “Circular Reference” in it.

Let’s look at an example of how to trigger this issue:

from drafter import *

@dataclass
class Item:
    name: str
    previously_seen: List['Item']

@dataclass
class State:
    items: List[Item]

# ...

first_item = Item("First Item", [])
second_item = Item("Second Item", [first_item])
first_item.previously_seen.append(second_item)
start_server(State([first_item, second_item]))

In this example, the first_item has a reference to the second_item and vice versa. This creates a circular reference between those elements. When Drafter tries to generate code to construct the instances, it would get stuck in an infinite loop trying to flatten everything. Instead, it chooses to generate the text "Circular Reference".

To fix this issue, you should first confirm that you need circular references. Circular references are extremely useful for a wide variety of purposes, such as representing a graph. If you do need them, you can manually write the unit tests for those cases, using the generated ones as a base. Capture the result of calling your route, and you can then test individual pieces by inspecting the state and content of the resulting Page object. See Testing Parts of Routes for more information.

However, it’s also very likely that you do not need circular references, and you added them by mistake. Review your code carefully to see if you are accidentally creating circular references. A few ways that this can happen:

• You are appending a list to itself.

• You set the field of an object to itself.

• You have an inner field or list element that refers to the outer object.