Fix ListSerializer.get_initial to return consistent initial list structure

[shrajal01]

This change updates ListSerializer.get_initial() to return an initial
list structure when initial_data is provided. The previous behavior
did not correctly handle list initialization and could result in
inconsistent initial states when rendering form-like serializers.

The updated implementation ensures:

• When initial_data is a list, an initial list structure is returned
• When no initial_data is provided, an empty list is returned
• No unintended conversion via to_representation()

This aligns ListSerializer behavior with Serializer.get_initial and
prevents incorrect input→output transformations.

[Copilot]

Pull Request Overview

This PR fixes ListSerializer.get_initial() to return a consistent initial list structure instead of using to_representation(), which could cause incorrect input→output transformations when rendering form-like serializers.

Key changes:

• Updated get_initial() to return a list of initial values from child serializers when initial_data is provided
• Added proper docstring explaining the method's behavior
• Removed the call to to_representation() that was causing inconsistent behavior

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[Copilot]

The return [] statement on line 620 is unreachable code. When hasattr(self, 'initial_data') is True, the code returns either on line 618 (if initial_data is a list) or on line 619 (if it's not a list). When the condition is False, execution jumps directly to line 620.

This results in redundant code since line 619 and line 620 both return the same empty list.

Suggested fix - remove line 619 and keep only line 620:

def get_initial(self):
    """
    Return a list of initial values, one for each item in `initial_data`,
    or an empty list if no input data was provided.
    """
    if hasattr(self, 'initial_data'):
        if isinstance(self.initial_data, list):
            return [self.child.get_initial() for _ in self.initial_data]
    return []

Suggested change

return []

[auvipy]

please add reference issue in the description section and appropriate unit tests for verifying the changes

[peterthomassen]

Thanks. I've added a comment where I think there's a problem.

Also, please add a test to demonstrate before/after behavior, and undo the unneeded whitespace changes. Thanks!

[peterthomassen]

This does not seem correct, as all the list items would be the same.