nushell/crates/nu-command/src/debug/inspect.rs

use super::inspect_table;
use nu_protocol::{
    ast::Call,
    engine::{Command, EngineState, Stack},
    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Type, Value,
};
use terminal_size::{terminal_size, Height, Width};

#[derive(Clone)]
pub struct Inspect;

impl Command for Inspect {
    fn name(&self) -> &str {
        "inspect"
    }

    fn usage(&self) -> &str {
        "Inspect pipeline results while running a pipeline."
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("inspect")
            .input_output_types(vec![(Type::Any, Type::Any)])
            .allow_variants_without_examples(true)
            .category(Category::Debug)
    }

    fn run(
        &self,
        _engine_state: &EngineState,
        _stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let input_metadata = input.metadata();
        let input_val = input.into_value(call.head);
        if input_val.is_nothing() {
            return Err(ShellError::PipelineEmpty {
                dst_span: call.head,
            });
        }
        let original_input = input_val.clone();
        let description = match input_val {
            Value::CustomValue { ref val, .. } => val.value_string(),
            _ => input_val.get_type().to_string(),
        };

        let (cols, _rows) = match terminal_size() {
            Some((w, h)) => (Width(w.0), Height(h.0)),
            None => (Width(0), Height(0)),
        };

        let table = inspect_table::build_table(input_val, description, cols.0 as usize);

        // Note that this is printed to stderr. The reason for this is so it doesn't disrupt the regular nushell
        // tabular output. If we printed to stdout, nushell would get confused with two outputs.
        eprintln!("{table}\n");

        Ok(original_input.into_pipeline_data_with_metadata(input_metadata))
    }

    fn examples(&self) -> Vec<Example> {
        vec![Example {
            description: "Inspect pipeline results",
            example: "ls | inspect | get name | inspect",
            result: None,
        }]
    }
}