nushell/crates/nu-cli/src/commands/run_alias.rs

use crate::commands::classified::block::run_block;
use crate::commands::WholeStreamCommand;
use crate::prelude::*;

use derive_new::new;
use nu_errors::ShellError;
use nu_protocol::{hir::Block, ReturnSuccess, Signature, SyntaxShape};

#[derive(new, Clone)]
pub struct AliasCommand {
    name: String,
    args: Vec<String>,
    block: Block,
}

#[async_trait]
impl WholeStreamCommand for AliasCommand {
    fn name(&self) -> &str {
        &self.name
    }

    fn signature(&self) -> Signature {
        let mut alias = Signature::build(&self.name);

        for arg in &self.args {
            alias = alias.optional(arg, SyntaxShape::Any, "");
        }

        alias
    }

    fn usage(&self) -> &str {
        ""
    }

    async fn run(
        &self,
        args: CommandArgs,
        registry: &CommandRegistry,
    ) -> Result<OutputStream, ShellError> {
        let tag = args.call_info.name_tag.clone();
        let call_info = args.call_info.clone();
        let registry = registry.clone();
        let block = self.block.clone();
        let alias_command = self.clone();
        let mut context = Context::from_args(&args, &registry);
        let input = args.input;

        let stream = async_stream! {
            let mut scope = call_info.scope.clone();
            let evaluated = call_info.evaluate(&registry).await?;
            if let Some(positional) = &evaluated.args.positional {
                for (pos, arg) in positional.iter().enumerate() {
                    scope.vars.insert(alias_command.args[pos].to_string(), arg.clone());
                }
            }

            let result = run_block(
                &block,
                &mut context,
                input,
                &scope.it,
                &scope.vars,
                &scope.env,
            ).await;

            match result {
                Ok(stream) if stream.is_empty() => {
                    yield Err(ShellError::labeled_error(
                        "Expected a block",
                        "alias needs a block",
                        tag,
                    ));
                }
                Ok(mut stream) => {
                    // We collect first to ensure errors are put into the context
                    while let Some(result) = stream.next().await {
                        yield Ok(ReturnSuccess::Value(result));
                    }

                    let errors = context.get_errors();
                    if let Some(x) = errors.first() {
                        yield Err(ShellError::labeled_error_with_secondary(
                            "Alias failed to run",
                            "alias failed to run",
                            tag.clone(),
                            x.to_string(),
                            tag
                        ));
                    }
                }
                Err(e) => {
                    yield Err(ShellError::labeled_error_with_secondary(
                        "Alias failed to run",
                        "alias failed to run",
                        tag.clone(),
                        e.to_string(),
                        tag
                    ));
                }
            }
        };

        Ok(stream.to_output_stream())
    }
}