nushell/crates/nu-cmd-dataframe/src/dataframe/eager/with_column.rs

use crate::dataframe::values::{Column, NuDataFrame, NuExpression, NuLazyFrame};
use nu_engine::command_prelude::*;

#[derive(Clone)]
pub struct WithColumn;

impl Command for WithColumn {
    fn name(&self) -> &str {
        "dfr with-column"
    }

    fn usage(&self) -> &str {
        "Adds a series to the dataframe."
    }

    fn signature(&self) -> Signature {
        Signature::build(self.name())
            .named("name", SyntaxShape::String, "new column name", Some('n'))
            .rest(
                "series or expressions",
                SyntaxShape::Any,
                "series to be added or expressions used to define the new columns",
            )
            .input_output_type(
                Type::Custom("dataframe".into()),
                Type::Custom("dataframe".into()),
            )
            .category(Category::Custom("dataframe or lazyframe".into()))
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Adds a series to the dataframe",
                example: r#"[[a b]; [1 2] [3 4]]
    | dfr into-df
    | dfr with-column ([5 6] | dfr into-df) --name c"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![
                            Column::new(
                                "a".to_string(),
                                vec![Value::test_int(1), Value::test_int(3)],
                            ),
                            Column::new(
                                "b".to_string(),
                                vec![Value::test_int(2), Value::test_int(4)],
                            ),
                            Column::new(
                                "c".to_string(),
                                vec![Value::test_int(5), Value::test_int(6)],
                            ),
                        ],
                        None,
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
            Example {
                description: "Adds a series to the dataframe",
                example: r#"[[a b]; [1 2] [3 4]]
    | dfr into-lazy
    | dfr with-column [
        ((dfr col a) * 2 | dfr as "c")
        ((dfr col a) * 3 | dfr as "d")
      ]
    | dfr collect"#,
                result: Some(
                    NuDataFrame::try_from_columns(
                        vec![
                            Column::new(
                                "a".to_string(),
                                vec![Value::test_int(1), Value::test_int(3)],
                            ),
                            Column::new(
                                "b".to_string(),
                                vec![Value::test_int(2), Value::test_int(4)],
                            ),
                            Column::new(
                                "c".to_string(),
                                vec![Value::test_int(2), Value::test_int(6)],
                            ),
                            Column::new(
                                "d".to_string(),
                                vec![Value::test_int(3), Value::test_int(9)],
                            ),
                        ],
                        None,
                    )
                    .expect("simple df for test should not fail")
                    .into_value(Span::test_data()),
                ),
            },
        ]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let value = input.into_value(call.head)?;
        if NuLazyFrame::can_downcast(&value) {
            let df = NuLazyFrame::try_from_value(value)?;
            command_lazy(engine_state, stack, call, df)
        } else if NuDataFrame::can_downcast(&value) {
            let df = NuDataFrame::try_from_value(value)?;
            command_eager(engine_state, stack, call, df)
        } else {
            Err(ShellError::CantConvert {
                to_type: "lazy or eager dataframe".into(),
                from_type: value.get_type().to_string(),
                span: value.span(),
                help: None,
            })
        }
    }
}

fn command_eager(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    mut df: NuDataFrame,
) -> Result<PipelineData, ShellError> {
    let new_column: Value = call.req(engine_state, stack, 0)?;
    let column_span = new_column.span();

    if NuExpression::can_downcast(&new_column) {
        let vals: Vec<Value> = call.rest(engine_state, stack, 0)?;
        let value = Value::list(vals, call.head);
        let expressions = NuExpression::extract_exprs(value)?;
        let lazy = NuLazyFrame::new(true, df.lazy().with_columns(&expressions));

        let df = lazy.collect(call.head)?;

        Ok(PipelineData::Value(df.into_value(call.head), None))
    } else {
        let mut other = NuDataFrame::try_from_value(new_column)?.as_series(column_span)?;

        let name = match call.get_flag::<String>(engine_state, stack, "name")? {
            Some(name) => name,
            None => other.name().to_string(),
        };

        let series = other.rename(&name).clone();

        df.as_mut()
            .with_column(series)
            .map_err(|e| ShellError::GenericError {
                error: "Error adding column to dataframe".into(),
                msg: e.to_string(),
                span: Some(column_span),
                help: None,
                inner: vec![],
            })
            .map(|df| {
                PipelineData::Value(
                    NuDataFrame::dataframe_into_value(df.clone(), call.head),
                    None,
                )
            })
    }
}

fn command_lazy(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    lazy: NuLazyFrame,
) -> Result<PipelineData, ShellError> {
    let vals: Vec<Value> = call.rest(engine_state, stack, 0)?;
    let value = Value::list(vals, call.head);
    let expressions = NuExpression::extract_exprs(value)?;

    let lazy: NuLazyFrame = lazy.into_polars().with_columns(&expressions).into();

    Ok(PipelineData::Value(
        NuLazyFrame::into_value(lazy, call.head)?,
        None,
    ))
}

#[cfg(test)]
mod test {
    use super::super::super::test_dataframe::test_dataframe;
    use super::*;
    use crate::dataframe::expressions::ExprAlias;
    use crate::dataframe::expressions::ExprCol;

    #[test]
    fn test_examples() {
        test_dataframe(vec![
            Box::new(WithColumn {}),
            Box::new(ExprAlias {}),
            Box::new(ExprCol {}),
        ])
    }
}