nushell/src/plugins/edit.rs

use nu::{
    serve_plugin, CallInfo, ColumnPath, Plugin, Primitive, ReturnSuccess, ReturnValue, ShellError,
    Signature, SpannedTypeName, SyntaxShape, UntaggedValue, Value,
};
use nu_source::Tagged;

struct Edit {
    field: Option<Tagged<ColumnPath>>,
    value: Option<UntaggedValue>,
}
impl Edit {
    fn new() -> Edit {
        Edit {
            field: None,
            value: None,
        }
    }

    fn edit(&self, value: Value) -> Result<Value, ShellError> {
        let value_tag = value.tag();
        match (value, self.value.clone()) {
            (
                obj @ Value {
                    value: UntaggedValue::Row(_),
                    ..
                },
                Some(v),
            ) => match &self.field {
                Some(f) => {
                    match obj.replace_data_at_column_path(&f, v.clone().into_untagged_value()) {
                        Some(v) => return Ok(v),
                        None => {
                            return Err(ShellError::labeled_error(
                                "edit could not find place to insert column",
                                "column name",
                                &f.tag,
                            ))
                        }
                    }
                }
                None => Err(ShellError::untagged_runtime_error(
                    "edit needs a column when changing a value in a table",
                )),
            },
            _ => Err(ShellError::labeled_error(
                "Unrecognized type in stream",
                "original value",
                value_tag,
            )),
        }
    }
}

impl Plugin for Edit {
    fn config(&mut self) -> Result<Signature, ShellError> {
        Ok(Signature::build("edit")
            .desc("Edit an existing column to have a new value.")
            .required(
                "Field",
                SyntaxShape::ColumnPath,
                "the name of the column to edit",
            )
            .required(
                "Value",
                SyntaxShape::String,
                "the new value to give the cell(s)",
            )
            .filter())
    }

    fn begin_filter(&mut self, call_info: CallInfo) -> Result<Vec<ReturnValue>, ShellError> {
        if let Some(args) = call_info.args.positional {
            match &args[0] {
                table @ Value {
                    value: UntaggedValue::Primitive(Primitive::ColumnPath(_)),
                    ..
                } => {
                    self.field = Some(table.as_column_path()?);
                }
                value => return Err(ShellError::type_error("table", value.spanned_type_name())),
            }

            match &args[1] {
                Value { value: v, .. } => {
                    self.value = Some(v.clone());
                }
            }
        }

        Ok(vec![])
    }

    fn filter(&mut self, input: Value) -> Result<Vec<ReturnValue>, ShellError> {
        Ok(vec![ReturnSuccess::value(self.edit(input)?)])
    }
}

fn main() {
    serve_plugin(&mut Edit::new());
}