fix: Array.sample() fails for List and nested Array inner types

[Copilot]

Array.sample() crashes when the inner type is List or nested Array:

class TestSchema(dy.Schema):
    a = dy.Array(dy.List(dy.Bool()), 2)

TestSchema.sample(1, generator=dy.random.Generator(0))
# InvalidOperationError: cannot reshape array of size 49 into shape (1, 2)

Root Cause

Series.reshape() operates on primitive element counts, not complex element counts. When sampling Array(List(Bool()), 2):

• Samples 2 Lists (each containing variable-length Bool sequences)
• Attempts reshape((1, 2)) on a Series containing 2 List objects
• Polars counts all nested Bool elements (e.g., 49) instead of the 2 List containers
• Reshape fails with size mismatch

Changes

• Array._sample_unchecked: Branch on isinstance(inner_dtype, (pl.List, pl.Array))

  • Complex types: Manual chunking via slice() + to_list(), construct with explicit dtype
  • Other types: Existing reshape() path (scalars, Struct)

• Tests: Parametrized coverage for Array(List(...)) and Array(Array(...))

Original prompt

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This section details on the original issue you should resolve

<issue_title>Sampling fails for columns of dtype Array(List(...), ...)</issue_title>
<issue_description>Consider:

def test_sample_array_list(arr_size, n_samples):
    class TestSchema(dy.Schema):
        a = dy.Array(dy.List(dy.Bool()), arr_size)
    TestSchema.sample(n_samples, generator=dy.random.Generator(0))

On dataframely==2.3.1:

• calling test_sample_array_list(2, 1)
  fails with polars.exceptions.InvalidOperationError: cannot reshape array of size 49 into shape (1, 2)
• and calling test_sample_array_list(1, 1)
  fails with polars.exceptions.SchemaError: type Boolean is incompatible with expected type List(Boolean)

I'd expect both to pass.</issue_description>

<agent_instructions>Fix the issue with as few changes as possible</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Sampling fails for columns of dtype Array(List(...), ...) #243

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