nushell/crates/nu-cli/src/commands/evaluate_by.rs
Jason Gedge 522a828687
Move external closer to internal (#1611)
* Refactor InputStream and affected commands.

First, making `values` private and leaning on the `Stream` implementation makes
consumes of `InputStream` less likely to have to change in the future, if we
change what an `InputStream` is internally.

Second, we're dropping `Option<InputStream>` as the input to pipelines,
internals, and externals. Instead, `InputStream.is_empty` can be used to check
for "emptiness". Empty streams are typically only ever used as the first input
to a pipeline.

* Add run_external internal command.

We want to push external commands closer to internal commands, eventually
eliminating the concept of "external" completely. This means we can consolidate
a couple of things:

- Variable evaluation (for example, `$it`, `$nu`, alias vars)
- Behaviour of whole stream vs per-item external execution

It should also make it easier for us to start introducing argument signatures
for external commands,

* Update run_external.rs

* Update run_external.rs

* Update run_external.rs

* Update run_external.rs

Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>
2020-04-20 15:30:44 +12:00

72 lines
2 KiB
Rust

use crate::commands::WholeStreamCommand;
use crate::prelude::*;
use crate::utils::data_processing::{evaluate, fetch};
use nu_errors::ShellError;
use nu_protocol::{ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
use nu_source::{SpannedItem, Tagged};
use nu_value_ext::ValueExt;
pub struct EvaluateBy;
#[derive(Deserialize)]
pub struct EvaluateByArgs {
evaluate_with: Option<Tagged<String>>,
}
impl WholeStreamCommand for EvaluateBy {
fn name(&self) -> &str {
"evaluate-by"
}
fn signature(&self) -> Signature {
Signature::build("evaluate-by").named(
"evaluate_with",
SyntaxShape::String,
"the name of the column to evaluate by",
Some('w'),
)
}
fn usage(&self) -> &str {
"Creates a new table with the data from the tables rows evaluated by the column given."
}
fn run(
&self,
args: CommandArgs,
registry: &CommandRegistry,
) -> Result<OutputStream, ShellError> {
args.process(registry, evaluate_by)?.run()
}
}
pub fn evaluate_by(
EvaluateByArgs { evaluate_with }: EvaluateByArgs,
RunnableContext { input, name, .. }: RunnableContext,
) -> Result<OutputStream, ShellError> {
let stream = async_stream! {
let values: Vec<Value> = input.collect().await;
if values.is_empty() {
yield Err(ShellError::labeled_error(
"Expected table from pipeline",
"requires a table input",
name
))
} else {
let evaluate_with = if let Some(evaluator) = evaluate_with {
Some(evaluator.item().clone())
} else {
None
};
match evaluate(&values[0], evaluate_with, name) {
Ok(evaluated) => yield ReturnSuccess::value(evaluated),
Err(err) => yield Err(err)
}
}
};
Ok(stream.to_output_stream())
}