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

use crate::commands::WholeStreamCommand;
use crate::context::CommandRegistry;
use crate::prelude::*;
use futures::stream::StreamExt;
use indexmap::IndexMap;
use nu_errors::ShellError;
use nu_protocol::Dictionary;
use nu_protocol::{ReturnSuccess, Signature, UntaggedValue, Value};

pub struct Headers;

impl WholeStreamCommand for Headers {
    fn name(&self) -> &str {
        "headers"
    }

    fn signature(&self) -> Signature {
        Signature::build("headers")
    }

    fn usage(&self) -> &str {
        "Use the first row of the table as column names"
    }

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

    fn examples(&self) -> Vec<Example> {
        vec![Example {
            description: "Create headers for a raw string",
            example: r#"echo "a b c|1 2 3" | split-row "|" | split-column " " | headers"#,
            result: None,
        }]
    }
}

pub fn headers(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
    let stream = async_stream! {
        let mut input = args.input;
        let rows: Vec<Value> = input.collect().await;

        if rows.len() < 1 {
            yield Err(ShellError::untagged_runtime_error("Couldn't find headers, was the input a properly formatted, non-empty table?"));
        }

        //the headers are the first row in the table
        let headers: Vec<String> = match &rows[0].value {
            UntaggedValue::Row(d) => {
                Ok(d.entries.iter().map(|(k, v)| {
                    match v.as_string() {
                        Ok(s) => s,
                        Err(_) => { //If a cell that should contain a header name is empty, we name the column Column[index]
                            match d.entries.get_full(k) {
                                Some((index, _, _)) => format!("Column{}", index),
                                None => "unknownColumn".to_string()
                            }
                        }
                    }
                }).collect())
            }
            _ => Err(ShellError::unexpected_eof("Could not get headers, is the table empty?", rows[0].tag.span))
        }?;

        //Each row is a dictionary with the headers as keys
        for r in rows.iter().skip(1) {
            match &r.value {
                UntaggedValue::Row(d) => {
                    let mut i = 0;
                    let mut entries = IndexMap::new();
                    for (_, v) in d.entries.iter() {
                        entries.insert(headers[i].clone(), v.clone());
                        i += 1;
                    }
                    yield Ok(ReturnSuccess::Value(UntaggedValue::Row(Dictionary{entries}).into_value(r.tag.clone())))
                }
                _ => yield Err(ShellError::unexpected_eof("Couldn't iterate through rows, was the input a properly formatted table?", r.tag.span))
            }
        }
    };

    Ok(stream.to_output_stream())
}

#[cfg(test)]
mod tests {
    use super::Headers;

    #[test]
    fn examples_work_as_expected() {
        use crate::examples::test as test_examples;

        test_examples(Headers {})
    }
}