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https://github.com/nushell/nushell.git
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c747ec75c9
# Description
When implementing a `Command`, one must also import all the types
present in the function signatures for `Command`. This makes it so that
we often import the same set of types in each command implementation
file. E.g., something like this:
```rust
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
ShellError, Signature, Span, Type, Value,
};
```
This PR adds the `nu_engine::command_prelude` module which contains the
necessary and commonly used types to implement a `Command`:
```rust
// command_prelude.rs
pub use crate::CallExt;
pub use nu_protocol::{
ast::{Call, CellPath},
engine::{Command, EngineState, Stack},
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};
```
This should reduce the boilerplate needed to implement a command and
also gives us a place to track the breadth of the `Command` API. I tried
to be conservative with what went into the prelude modules, since it
might be hard/annoying to remove items from the prelude in the future.
Let me know if something should be included or excluded.
119 lines
3.6 KiB
Rust
119 lines
3.6 KiB
Rust
use crate::dataframe::values::{utils::DEFAULT_ROWS, Column, NuDataFrame, NuExpression};
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use nu_engine::command_prelude::*;
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#[derive(Clone)]
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pub struct LastDF;
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impl Command for LastDF {
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fn name(&self) -> &str {
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"dfr last"
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}
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fn usage(&self) -> &str {
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"Creates new dataframe with tail rows or creates a last expression."
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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("rows", SyntaxShape::Int, "Number of rows for tail")
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.input_output_types(vec![
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(
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Type::Custom("expression".into()),
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Type::Custom("expression".into()),
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),
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(
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Type::Custom("dataframe".into()),
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Type::Custom("dataframe".into()),
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),
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])
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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: "Create new dataframe with last rows",
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example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr last 1",
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result: Some(
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NuDataFrame::try_from_columns(
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vec![
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Column::new("a".to_string(), vec![Value::test_int(3)]),
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Column::new("b".to_string(), vec![Value::test_int(4)]),
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],
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None,
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)
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.expect("simple df for test 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: "Creates a last expression from a column",
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example: "dfr col a | dfr last",
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result: None,
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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 value = input.into_value(call.head);
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if NuDataFrame::can_downcast(&value) {
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let df = NuDataFrame::try_from_value(value)?;
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command(engine_state, stack, call, df)
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} else {
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let expr = NuExpression::try_from_value(value)?;
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let expr: NuExpression = expr.into_polars().last().into();
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Ok(PipelineData::Value(
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NuExpression::into_value(expr, call.head),
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None,
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))
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}
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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(DEFAULT_ROWS);
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let res = df.as_ref().tail(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::{build_test_engine_state, test_dataframe_example};
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use super::*;
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use crate::dataframe::lazy::aggregate::LazyAggregate;
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use crate::dataframe::lazy::groupby::ToLazyGroupBy;
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#[test]
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fn test_examples_dataframe() {
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let mut engine_state = build_test_engine_state(vec![Box::new(LastDF {})]);
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test_dataframe_example(&mut engine_state, &LastDF.examples()[0]);
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}
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#[test]
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fn test_examples_expression() {
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let mut engine_state = build_test_engine_state(vec![
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Box::new(LastDF {}),
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Box::new(LazyAggregate {}),
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Box::new(ToLazyGroupBy {}),
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]);
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test_dataframe_example(&mut engine_state, &LastDF.examples()[1]);
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}
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}
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