nushell/src/commands/which_.rs

use crate::commands::WholeStreamCommand;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{Primitive, Signature, SyntaxShape, UntaggedValue, Value};

pub struct Which;

impl WholeStreamCommand for Which {
    fn name(&self) -> &str {
        "which"
    }

    fn signature(&self) -> Signature {
        Signature::build("which").required(
            "name",
            SyntaxShape::Any,
            "the name of the command to find the path to",
        )
    }

    fn usage(&self) -> &str {
        "Finds a program file."
    }

    fn run(
        &self,
        args: CommandArgs,
        registry: &CommandRegistry,
    ) -> Result<OutputStream, ShellError> {
        which(args, registry)
    }
}

pub fn which(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
    let args = args.evaluate_once(registry)?;

    let mut which_out = VecDeque::new();
    let tag = args.call_info.name_tag.clone();

    if let Some(v) = &args.call_info.args.positional {
        if !v.is_empty() {
            match &v[0] {
                Value {
                    value: UntaggedValue::Primitive(Primitive::String(s)),
                    tag,
                } => {
                    if let Ok(ok) = which::which(&s) {
                        which_out.push_back(
                            UntaggedValue::Primitive(Primitive::Path(ok)).into_value(tag.clone()),
                        );
                    }
                }
                Value { tag, .. } => {
                    return Err(ShellError::labeled_error(
                        "Expected a filename to find",
                        "needs a filename",
                        tag,
                    ));
                }
            }
        } else {
            return Err(ShellError::labeled_error(
                "Expected a binary to find",
                "needs application name",
                tag,
            ));
        }
    } else {
        return Err(ShellError::labeled_error(
            "Expected a binary to find",
            "needs application name",
            tag,
        ));
    }

    Ok(which_out.to_output_stream())
}