nushell/src/commands/first.rs

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Rust
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use crate::errors::ShellError;
use crate::prelude::*;
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// TODO: "Amount remaining" wrapper
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pub fn first(args: CommandArgs) -> Result<OutputStream, ShellError> {
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if args.len() == 0 {
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return Err(ShellError::maybe_labeled_error(
"First requires an amount",
"needs parameter",
args.name_span,
));
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}
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let amount = args.expect_nth(0)?.as_i64();
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let amount = match amount {
Ok(o) => o,
Err(_) => {
return Err(ShellError::labeled_error(
"Value is not a number",
"expected integer",
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args.expect_nth(0)?.span,
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))
}
};
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let input = args.input;
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Ok(input
.take(amount as u64)
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.map(|v| ReturnValue::Value(v))
.boxed())
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}