use nu_engine::CallExt;
use nu_protocol::ast::{Call, CellPath, PathMember};
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
PipelineIterator, ShellError, Signature, Span, SyntaxShape, Type, Value,
};
use std::collections::HashSet;
#[derive(Clone)]
pub struct Select;
impl Command for Select {
fn name(&self) -> &str {
"select"
}
fn signature(&self) -> Signature {
Signature::build("select")
.input_output_types(vec![
(Type::Record(vec![]), Type::Record(vec![])),
(Type::Table(vec![]), Type::Table(vec![])),
])
.switch(
"ignore-errors",
"ignore missing data (make all cell path members optional)",
Some('i'),
)
.rest(
"rest",
SyntaxShape::CellPath,
"the columns to select from the table",
)
.category(Category::Filters)
}
fn usage(&self) -> &str {
"Select only these columns or rows from the input. Opposite of `reject`."
}
fn extra_usage(&self) -> &str {
r#"This differs from `get` in that, rather than accessing the given value in the data structure,
it removes all non-selected values from the structure. Hence, using `select` on a table will
produce a table, a list will produce a list, and a record will produce a record."#
}
fn search_terms(&self) -> Vec<&str> {
vec!["pick", "choose", "get"]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let mut columns: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
let ignore_errors = call.has_flag("ignore-errors");
let span = call.head;
if ignore_errors {
for cell_path in &mut columns {
cell_path.make_optional();
}
}
select(engine_state, span, columns, input)
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "Select a column in a table",
example: "[{a: a b: b}] | select a",
result: Some(Value::List {
vals: vec![Value::test_record(vec!["a"], vec![Value::test_string("a")])],
span: Span::test_data(),
}),
},
Example {
description: "Select a field in a record",
example: "{a: a b: b} | select a",
result: Some(Value::test_record(vec!["a"], vec![Value::test_string("a")])),
},
Example {
description: "Select just the `name` column",
example: "ls | select name",
result: None,
},
Example {
description: "Select the first four rows (this is the same as `first 4`)",
example: "ls | select 0 1 2 3",
result: None,
},
]
}
}
fn select(
engine_state: &EngineState,
call_span: Span,
columns: Vec<CellPath>,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let mut unique_rows: HashSet<usize> = HashSet::new();
let mut new_columns = vec![];
for column in columns {
let CellPath { ref members } = column;
match members.get(0) {
Some(PathMember::Int { val, span, .. }) => {
if members.len() > 1 {
return Err(ShellError::GenericError(
"Select only allows row numbers for rows".into(),
"extra after row number".into(),
Some(*span),
None,
Vec::new(),
));
}
if unique_rows.contains(val) {
return Err(ShellError::GenericError(
"Select can't get the same row twice".into(),
"duplicated row index".into(),
Some(*span),
None,
Vec::new(),
));
}
unique_rows.insert(*val);
}
_ => new_columns.push(column),
};
}
let columns = new_columns;
let mut unique_rows: Vec<usize> = unique_rows.into_iter().collect();
let input = if !unique_rows.is_empty() {
unique_rows.sort_unstable();
let metadata = input.metadata();
let pipeline_iter: PipelineIterator = input.into_iter();
NthIterator {
input: pipeline_iter,
rows: unique_rows,
skip: false,
current: 0,
}
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata)
} else {
input
};
match input {
PipelineData::Value(
Value::List {
vals: input_vals,
span,
},
metadata,
..,
) => {
let mut output = vec![];
let mut columns_with_value = Vec::new();
for input_val in input_vals {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for path in &columns {
match input_val.clone().follow_cell_path(&path.members, false) {
Ok(fetcher) => {
cols.push(path.into_string().replace('.', "_"));
vals.push(fetcher);
if !columns_with_value.contains(&path) {
columns_with_value.push(path);
}
}
Err(e) => {
return Err(e);
}
}
}
output.push(Value::Record { cols, vals, span })
} else {
output.push(input_val)
}
}
Ok(output
.into_iter()
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata))
}
PipelineData::ListStream(stream, metadata, ..) => {
let mut values = vec![];
for x in stream {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for path in &columns {
match x.clone().follow_cell_path(&path.members, false) {
Ok(value) => {
cols.push(path.into_string().replace('.', "_"));
vals.push(value);
}
Err(e) => return Err(e),
}
}
values.push(Value::Record {
cols,
vals,
span: call_span,
});
} else {
values.push(x);
}
}
Ok(values
.into_pipeline_data(engine_state.ctrlc.clone())
.set_metadata(metadata))
}
PipelineData::Value(v, metadata, ..) => {
if !columns.is_empty() {
let mut cols = vec![];
let mut vals = vec![];
for cell_path in columns {
match v.clone().follow_cell_path(&cell_path.members, false) {
Ok(result) => {
cols.push(cell_path.into_string().replace('.', "_"));
vals.push(result);
}
Err(e) => return Err(e),
}
}
Ok(Value::Record {
cols,
vals,
span: call_span,
}
.into_pipeline_data()
.set_metadata(metadata))
} else {
Ok(v.into_pipeline_data().set_metadata(metadata))
}
}
_ => Ok(PipelineData::empty()),
}
}
struct NthIterator {
input: PipelineIterator,
rows: Vec<usize>,
skip: bool,
current: usize,
}
impl Iterator for NthIterator {
type Item = Value;
fn next(&mut self) -> Option<Self::Item> {
loop {
if !self.skip {
if let Some(row) = self.rows.first() {
if self.current == *row {
self.rows.remove(0);
self.current += 1;
return self.input.next();
} else {
self.current += 1;
let _ = self.input.next();
continue;
}
} else {
return None;
}
} else if let Some(row) = self.rows.first() {
if self.current == *row {
self.rows.remove(0);
self.current += 1;
let _ = self.input.next();
continue;
} else {
self.current += 1;
return self.input.next();
}
} else {
return self.input.next();
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Select)
}
}