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.
128 lines
4.2 KiB
Rust
128 lines
4.2 KiB
Rust
use crate::dataframe::values::NuDataFrame;
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use nu_engine::command_prelude::*;
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use polars::{prelude::NamedFrom, series::Series};
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#[derive(Clone)]
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pub struct SampleDF;
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impl Command for SampleDF {
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fn name(&self) -> &str {
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"dfr sample"
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}
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fn usage(&self) -> &str {
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"Create sample dataframe."
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}
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fn signature(&self) -> Signature {
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Signature::build(self.name())
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.named(
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"n-rows",
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SyntaxShape::Int,
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"number of rows to be taken from dataframe",
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Some('n'),
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)
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.named(
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"fraction",
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SyntaxShape::Number,
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"fraction of dataframe to be taken",
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Some('f'),
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)
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.named(
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"seed",
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SyntaxShape::Number,
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"seed for the selection",
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Some('s'),
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)
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.switch("replace", "sample with replace", Some('e'))
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.switch("shuffle", "shuffle sample", Some('u'))
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.input_output_type(
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Type::Custom("dataframe".into()),
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Type::Custom("dataframe".into()),
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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: "Sample rows from dataframe",
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example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr sample --n-rows 1",
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result: None, // No expected value because sampling is random
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},
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Example {
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description: "Shows sample row using fraction and replace",
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example:
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"[[a b]; [1 2] [3 4] [5 6]] | dfr into-df | dfr sample --fraction 0.5 --replace",
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result: None, // No expected value because sampling is random
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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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command(engine_state, stack, call, input)
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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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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let rows: Option<Spanned<i64>> = call.get_flag(engine_state, stack, "n-rows")?;
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let fraction: Option<Spanned<f64>> = call.get_flag(engine_state, stack, "fraction")?;
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let seed: Option<u64> = call
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.get_flag::<i64>(engine_state, stack, "seed")?
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.map(|val| val as u64);
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let replace: bool = call.has_flag(engine_state, stack, "replace")?;
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let shuffle: bool = call.has_flag(engine_state, stack, "shuffle")?;
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let df = NuDataFrame::try_from_pipeline(input, call.head)?;
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match (rows, fraction) {
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(Some(rows), None) => df
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.as_ref()
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.sample_n(&Series::new("s", &[rows.item]), replace, shuffle, seed)
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.map_err(|e| ShellError::GenericError {
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error: "Error creating sample".into(),
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msg: e.to_string(),
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span: Some(rows.span),
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help: None,
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inner: vec![],
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}),
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(None, Some(frac)) => df
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.as_ref()
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.sample_frac(&Series::new("frac", &[frac.item]), replace, shuffle, seed)
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.map_err(|e| ShellError::GenericError {
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error: "Error creating sample".into(),
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msg: e.to_string(),
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span: Some(frac.span),
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help: None,
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inner: vec![],
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}),
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(Some(_), Some(_)) => Err(ShellError::GenericError {
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error: "Incompatible flags".into(),
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msg: "Only one selection criterion allowed".into(),
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span: Some(call.head),
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help: None,
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inner: vec![],
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}),
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(None, None) => Err(ShellError::GenericError {
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error: "No selection".into(),
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msg: "No selection criterion was found".into(),
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span: Some(call.head),
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help: Some("Perhaps you want to use the flag -n or -f".into()),
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inner: vec![],
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}),
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}
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.map(|df| PipelineData::Value(NuDataFrame::dataframe_into_value(df, call.head), None))
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}
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