Files
nushell/crates/nu-cmd-dataframe/src/dataframe/eager/columns.rs
Ian Manske c747ec75c9 Add command_prelude module (#12291)
# 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.
2024-03-26 21:17:30 +00:00

74 lines
1.7 KiB
Rust

use crate::dataframe::values::NuDataFrame;
use nu_engine::command_prelude::*;
#[derive(Clone)]
pub struct ColumnsDF;
impl Command for ColumnsDF {
fn name(&self) -> &str {
"dfr columns"
}
fn usage(&self) -> &str {
"Show dataframe columns."
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.input_output_type(Type::Custom("dataframe".into()), Type::Any)
.category(Category::Custom("dataframe".into()))
}
fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Dataframe columns",
example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr columns",
result: Some(Value::list(
vec![Value::test_string("a"), Value::test_string("b")],
Span::test_data(),
)),
}]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
command(engine_state, stack, call, input)
}
}
fn command(
_engine_state: &EngineState,
_stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let df = NuDataFrame::try_from_pipeline(input, call.head)?;
let names: Vec<Value> = df
.as_ref()
.get_column_names()
.iter()
.map(|v| Value::string(*v, call.head))
.collect();
let names = Value::list(names, call.head);
Ok(PipelineData::Value(names, None))
}
#[cfg(test)]
mod test {
use super::super::super::test_dataframe::test_dataframe;
use super::*;
#[test]
fn test_examples() {
test_dataframe(vec![Box::new(ColumnsDF {})])
}
}