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

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use crate::commands::WholeStreamCommand;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{Signature, SyntaxShape, UntaggedValue, Value};
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#[derive(Deserialize)]
struct PrependArgs {
row: Value,
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}
pub struct Prepend;
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#[async_trait]
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impl WholeStreamCommand for Prepend {
fn name(&self) -> &str {
"prepend"
}
fn signature(&self) -> Signature {
Signature::build("prepend").required(
"row value",
SyntaxShape::Any,
"the value of the row to prepend to the table",
)
}
fn usage(&self) -> &str {
"Prepend the given row to the front of the table"
}
async fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
prepend(args).await
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}
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fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Add something to the beginning of a list or table",
example: "echo [2 3 4] | prepend 1",
result: Some(vec![
UntaggedValue::int(1).into(),
UntaggedValue::int(2).into(),
UntaggedValue::int(3).into(),
UntaggedValue::int(4).into(),
]),
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}]
}
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}
async fn prepend(args: CommandArgs) -> Result<OutputStream, ShellError> {
let (PrependArgs { row }, input) = args.process().await?;
let bos = futures::stream::iter(vec![row]);
Ok(bos.chain(input).to_output_stream())
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}
#[cfg(test)]
mod tests {
use super::Prepend;
use super::ShellError;
#[test]
fn examples_work_as_expected() -> Result<(), ShellError> {
use crate::examples::test as test_examples;
Ok(test_examples(Prepend {})?)
}
}