nushell/crates/nu-command/src/filters/get.rs

use nu_engine::CallExt;
use nu_protocol::ast::{Call, CellPath};
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData, Signature,
    SyntaxShape, Value,
};

#[derive(Clone)]
pub struct Get;

impl Command for Get {
    fn name(&self) -> &str {
        "get"
    }

    fn usage(&self) -> &str {
        "Extract data using a cell path."
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("get")
            .required(
                "cell_path",
                SyntaxShape::CellPath,
                "the cell path to the data",
            )
            .rest("rest", SyntaxShape::CellPath, "additional cell paths")
            .switch(
                "ignore-errors",
                "return nothing if path can't be found",
                Some('i'),
            )
            .category(Category::Filters)
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
        let span = call.head;
        let cell_path: CellPath = call.req(engine_state, stack, 0)?;
        let rest: Vec<CellPath> = call.rest(engine_state, stack, 1)?;
        let ignore_errors = call.has_flag("ignore-errors");
        let ctrlc = engine_state.ctrlc.clone();
        let metadata = input.metadata();

        if rest.is_empty() {
            let output = input
                .follow_cell_path(&cell_path.members, call.head)
                .map(|x| x.into_pipeline_data());

            if ignore_errors {
                match output {
                    Ok(output) => Ok(output),
                    Err(_) => Ok(Value::Nothing { span: call.head }.into_pipeline_data()),
                }
            } else {
                output
            }
        } else {
            let mut output = vec![];

            let paths = vec![cell_path].into_iter().chain(rest);

            let input = input.into_value(span);

            for path in paths {
                let val = input.clone().follow_cell_path(&path.members);

                if ignore_errors {
                    if let Ok(val) = val {
                        output.push(val);
                    }
                } else {
                    output.push(val?);
                }
            }

            Ok(output.into_iter().into_pipeline_data(ctrlc))
        }
        .map(|x| x.set_metadata(metadata))
    }
    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Extract the name of files as a list",
                example: "ls | get name",
                result: None,
            },
            Example {
                description: "Extract the name of the 3rd entry of a file list",
                example: "ls | get name.2",
                result: None,
            },
            Example {
                description: "Extract the name of the 3rd entry of a file list (alternative)",
                example: "ls | get 2.name",
                result: None,
            },
            Example {
                description: "Extract the cpu list from the sys information record",
                example: "sys | get cpu",
                result: None,
            },
        ]
    }
}