`infer_schema_length=None` fails with unexpected type for nested data

[theelderbeever]

`infer_schema_length=None` fails with unexpected type for nested data

[cmdlineluser]

Can reproduce.

pl.DataFrame({"A": [[[1.0], [2]]]})
# shape: (1, 1)
# ┌─────────────────┐
# │ A               │
# │ ---             │
# │ list[list[f64]] │
# ╞═════════════════╡
# │ [[1.0], [2.0]]  │
# └─────────────────┘

pl.DataFrame({"A": [[{"B":1.0}, {"B":2}]]})
TypeError: unexpected value while building Series of type Float64; found value of type Int64: 2

INFER_SCHEMA_LENGTH is hardcoded to 25 here, but it doesn't seem to come into play:

• polars/py-polars/src/conversion/any_value.rs

  Lines 289 to 290 in bfcc1ee

  	} else if ob.is_instance_of::<PyList>() | ob.is_instance_of::<PyTuple>() {
  	const INFER_SCHEMA_LENGTH: usize = 25;

The issue seems to be that structs are treated differently to other types.

• polars/crates/polars-core/src/series/any_value.rs

  Line 485 in bfcc1ee

  fn any_values_to_list(

• polars/crates/polars-core/src/series/any_value.rs

  Line 622 in bfcc1ee

  fn any_values_to_struct(

e.g. inside to_list there is an explicit cast:

• polars/crates/polars-core/src/series/any_value.rs

  Lines 514 to 515 in bfcc1ee

  	} else {
  	match b.cast(inner_type) {

But to_struct ends up calling from_any_values_and_dtype again on the inner values:

• polars/crates/polars-core/src/series/any_value.rs

  Line 688 in bfcc1ee

  Series::from_any_values_and_dtype(field.name(), &field_avs, &field.dtype, strict)?

So in this case, we end up with a strict call on the inner values that fails.

Series::from_any_values_and_dtype("name", [1.0, 2], Float64, true)