nu_plugin_polars 0.112.0

Nushell dataframe plugin commands based on polars.
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use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
use nu_protocol::shell_error::generic::GenericError;
use nu_protocol::{
    Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
};

use crate::PolarsPlugin;
use crate::values::{CustomValueSupport, PolarsPluginType};

use crate::values::utils::convert_columns_string;
use crate::values::{Column, NuDataFrame};

#[derive(Clone)]
pub struct DropNulls;

impl PluginCommand for DropNulls {
    type Plugin = PolarsPlugin;

    fn name(&self) -> &str {
        "polars drop-nulls"
    }

    fn description(&self) -> &str {
        "Drops null values in dataframe."
    }

    fn signature(&self) -> Signature {
        Signature::build(self.name())
            .optional(
                "subset",
                SyntaxShape::Table(vec![]),
                "Subset of columns to drop nulls.",
            )
            .input_output_types(vec![
                (
                    PolarsPluginType::NuDataFrame.into(),
                    PolarsPluginType::NuDataFrame.into(),
                ),
                (
                    PolarsPluginType::NuLazyFrame.into(),
                    PolarsPluginType::NuLazyFrame.into(),
                ),
            ])
            .category(Category::Custom("dataframe".into()))
    }

    fn examples(&self) -> Vec<Example<'_>> {
        vec![
            Example {
                description: "drop null values in dataframe",
                example: r#"let df = ([[a b]; [1 2] [3 0] [1 2]] | polars into-df);
    let res = ($df.b / $df.b);
    let a = ($df | polars with-column $res --name res);
    $a | polars drop-nulls"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![
                            Column::new(
                                "a".to_string(),
                                vec![Value::test_int(1), Value::test_int(1)],
                            ),
                            Column::new(
                                "b".to_string(),
                                vec![Value::test_int(2), Value::test_int(2)],
                            ),
                            Column::new(
                                "res".to_string(),
                                vec![Value::test_int(1), Value::test_int(1)],
                            ),
                        ],
                        None,
                        Span::test_data(),
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
            Example {
                description: "drop null values in dataframe",
                example: r#"let s = ([1 2 0 0 3 4] | polars into-df);
    ($s / $s) | polars drop-nulls"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![Column::new(
                            "div_0_0".to_string(),
                            vec![
                                Value::test_int(1),
                                Value::test_int(1),
                                Value::test_int(1),
                                Value::test_int(1),
                            ],
                        )],
                        None,
                        Span::test_data(),
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
        ]
    }

    fn run(
        &self,
        plugin: &Self::Plugin,
        engine: &EngineInterface,
        call: &EvaluatedCall,
        mut input: PipelineData,
    ) -> Result<PipelineData, LabeledError> {
        let metadata = input.take_metadata();
        command(plugin, engine, call, input)
            .map_err(LabeledError::from)
            .map(|pd| pd.set_metadata(metadata))
    }
}

fn command(
    plugin: &PolarsPlugin,
    engine: &EngineInterface,
    call: &EvaluatedCall,
    input: PipelineData,
) -> Result<PipelineData, ShellError> {
    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;

    let columns: Option<Vec<Value>> = call.opt(0)?;

    let (subset, col_span) = match columns {
        Some(cols) => {
            let (agg_string, col_span) = convert_columns_string(cols, call.head)?;
            (Some(agg_string), col_span)
        }
        None => (None, call.head),
    };

    let subset_slice = subset.as_ref().map(|cols| &cols[..]);

    let polars_df = df.as_ref().drop_nulls(subset_slice).map_err(|e| {
        ShellError::Generic(GenericError::new(
            "Error dropping nulls",
            e.to_string(),
            col_span,
        ))
    })?;
    let df = NuDataFrame::new(df.from_lazy, polars_df);
    df.to_pipeline_data(plugin, engine, call.head)
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::test::test_polars_plugin_command;

    #[test]
    fn test_examples() -> Result<(), ShellError> {
        test_polars_plugin_command(&DropNulls)
    }
}