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.
93 lines
2.6 KiB
Rust
93 lines
2.6 KiB
Rust
use crate::dataframe::values::{Column, NuDataFrame, NuLazyFrame};
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use nu_engine::command_prelude::*;
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#[derive(Clone)]
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pub struct LazyFetch;
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impl Command for LazyFetch {
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fn name(&self) -> &str {
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"dfr fetch"
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}
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fn usage(&self) -> &str {
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"Collects the lazyframe to the selected 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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.required(
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"rows",
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SyntaxShape::Int,
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"number of rows to be fetched from lazyframe",
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)
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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("lazyframe".into()))
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Fetch a rows from the dataframe",
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example: "[[a b]; [6 2] [4 2] [2 2]] | dfr into-df | dfr fetch 2",
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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(
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"a".to_string(),
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vec![Value::test_int(6), Value::test_int(4)],
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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(2)],
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),
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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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}
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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 rows: i64 = call.req(engine_state, stack, 0)?;
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let lazy = NuLazyFrame::try_from_pipeline(input, call.head)?;
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let eager: NuDataFrame = lazy
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.into_polars()
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.fetch(rows as usize)
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.map_err(|e| ShellError::GenericError {
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error: "Error fetching rows".into(),
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msg: e.to_string(),
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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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.into();
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Ok(PipelineData::Value(
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NuDataFrame::into_value(eager, call.head),
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None,
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))
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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(LazyFetch {})])
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}
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}
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