forked from extern/nushell
106 lines
3.1 KiB
Rust
106 lines
3.1 KiB
Rust
use super::super::values::{Column, NuDataFrame};
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use nu_engine::CallExt;
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use nu_protocol::{
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ast::Call,
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engine::{Command, EngineState, Stack},
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Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
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};
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#[derive(Clone)]
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pub struct FirstDF;
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impl Command for FirstDF {
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fn name(&self) -> &str {
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"first"
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}
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fn usage(&self) -> &str {
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"Show only the first number of rows."
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}
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fn signature(&self) -> Signature {
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Signature::build(self.name())
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.optional(
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"rows",
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SyntaxShape::Int,
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"starting from the front, the number of rows to return",
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)
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.input_type(Type::Custom("dataframe".into()))
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.output_type(Type::Custom("dataframe".into()))
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.category(Category::Custom("dataframe".into()))
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}
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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description: "Return the first row of a dataframe",
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example: "[[a b]; [1 2] [3 4]] | into df | first",
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result: Some(
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NuDataFrame::try_from_columns(vec![
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Column::new("a".to_string(), vec![Value::test_int(1)]),
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Column::new("b".to_string(), vec![Value::test_int(2)]),
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])
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.expect("should not fail")
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.into_value(Span::test_data()),
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),
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},
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Example {
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description: "Return the first two rows of a dataframe",
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example: "[[a b]; [1 2] [3 4]] | into df | first 2",
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result: Some(
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NuDataFrame::try_from_columns(vec![
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Column::new(
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"a".to_string(),
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vec![Value::test_int(1), Value::test_int(3)],
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),
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Column::new(
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"b".to_string(),
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vec![Value::test_int(2), Value::test_int(4)],
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),
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])
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.expect("should not fail")
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.into_value(Span::test_data()),
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),
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},
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]
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}
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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let df = NuDataFrame::try_from_pipeline(input, call.head)?;
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command(engine_state, stack, call, df)
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}
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}
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fn command(
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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df: NuDataFrame,
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) -> Result<PipelineData, ShellError> {
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let rows: Option<usize> = call.opt(engine_state, stack, 0)?;
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let rows = rows.unwrap_or(1);
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let res = df.as_ref().head(Some(rows));
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Ok(PipelineData::Value(
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NuDataFrame::dataframe_into_value(res, call.head),
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None,
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))
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}
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#[cfg(test)]
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mod test {
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use super::super::super::test_dataframe::test_dataframe;
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use super::*;
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#[test]
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fn test_examples() {
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test_dataframe(vec![Box::new(FirstDF {})])
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}
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}
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