use nu_engine::CallExt;
use nu_protocol::ast::{Call, CellPath, PathMember};
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
PipelineIterator, Record, ShellError, Signature, Span, SyntaxShape, Type, Value,
};
use std::collections::BTreeSet;
#[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![])),
(Type::List(Box::new(Type::Any)), Type::Any),
])
.switch(
"ignore-errors",
"ignore missing data (make all cell path members optional)",
Some('i'),
)
.rest(
"rest",
SyntaxShape::OneOf(vec![
SyntaxShape::CellPath,
SyntaxShape::List(Box::new(SyntaxShape::CellPath)),
]),
"The columns to select from the table.",
)
.allow_variants_without_examples(true)
.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 columns: Vec<Value> = call.rest(engine_state, stack, 0)?;
let mut new_columns: Vec<CellPath> = vec![];
for col_val in columns {
let col_span = &col_val.span();
match col_val {
Value::CellPath { val, .. } => {
new_columns.push(val);
}
Value::List { vals, .. } => {
for value in vals {
let val_span = &value.span();
match value {
Value::String { val, .. } => {
let cv = CellPath {
members: vec![PathMember::String {
val: val.clone(),
span: *val_span,
optional: false,
}],
};
new_columns.push(cv.clone());
}
Value::Int { val, .. } => {
let cv = CellPath {
members: vec![PathMember::Int {
val: val as usize,
span: *val_span,
optional: false,
}],
};
new_columns.push(cv.clone());
}
Value::CellPath { val, .. } => {
new_columns.push(val);
}
y => {
return Err(ShellError::CantConvert {
to_type: "cell path".into(),
from_type: y.get_type().to_string(),
span: y.span(),
help: None,
});
}
}
}
}
Value::String { val, .. } => {
let cv = CellPath {
members: vec![PathMember::String {
val: val.clone(),
span: *col_span,
optional: false,
}],
};
new_columns.push(cv.clone());
}
Value::Int { val, .. } => {
let cv = CellPath {
members: vec![PathMember::Int {
val: val as usize,
span: *col_span,
optional: false,
}],
};
new_columns.push(cv.clone());
}
x => {
return Err(ShellError::CantConvert {
to_type: "cell path".into(),
from_type: x.get_type().to_string(),
span: x.span(),
help: None,
});
}
}
}
let ignore_errors = call.has_flag(engine_state, stack, "ignore-errors")?;
let span = call.head;
if ignore_errors {
for cell_path in &mut new_columns {
cell_path.make_optional();
}
}
select(engine_state, span, new_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::test_list(
vec![Value::test_record(record! {
"a" => Value::test_string("a")
})],
)),
},
Example {
description: "Select a field in a record",
example: "{a: a b: b} | select a",
result: Some(Value::test_record(record! {
"a" => 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,
},
Example {
description: "Select columns by a provided list of columns",
example: "let cols = [name type];[[name type size]; [Cargo.toml toml 1kb] [Cargo.lock toml 2kb]] | select $cols",
result: None
},
Example {
description: "Select columns by a provided list of columns",
example: r#"[[name type size]; [Cargo.toml toml 1kb] [Cargo.lock toml 2kb]] | select ["name", "type"]"#,
result: Some(Value::test_list(
vec![
Value::test_record(record! {"name" => Value::test_string("Cargo.toml"), "type" => Value::test_string("toml")}),
Value::test_record(record! {"name" => Value::test_string("Cargo.lock"), "type" => Value::test_string("toml")})],
))
},
Example {
description: "Select rows by a provided list of rows",
example: "let rows = [0 2];[[name type size]; [Cargo.toml toml 1kb] [Cargo.lock toml 2kb] [file.json json 3kb]] | select $rows",
result: None
},
]
}
}
fn select(
engine_state: &EngineState,
call_span: Span,
columns: Vec<CellPath>,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let mut unique_rows: BTreeSet<usize> = BTreeSet::new();
let mut new_columns = vec![];
for column in columns {
let CellPath { ref members } = column;
match members.first() {
Some(PathMember::Int { val, span, .. }) => {
if members.len() > 1 {
return Err(ShellError::GenericError {
error: "Select only allows row numbers for rows".into(),
msg: "extra after row number".into(),
span: Some(*span),
help: None,
inner: vec![],
});
}
unique_rows.insert(*val);
}
_ => {
if !new_columns.contains(&column) {
new_columns.push(column)
}
}
};
}
let columns = new_columns;
let input = if !unique_rows.is_empty() {
let metadata = input.metadata();
let pipeline_iter: PipelineIterator = input.into_iter();
NthIterator {
input: pipeline_iter,
rows: unique_rows.into_iter().peekable(),
current: 0,
}
.into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone())
} else {
input
};
match input {
PipelineData::Value(v, metadata, ..) => {
let span = v.span();
match v {
Value::List {
vals: input_vals, ..
} => {
let mut output = vec![];
let mut columns_with_value = Vec::new();
for input_val in input_vals {
if !columns.is_empty() {
let mut record = Record::new();
for path in &columns {
match input_val.clone().follow_cell_path(&path.members, false) {
Ok(fetcher) => {
record.push(path.to_string().replace('.', "_"), fetcher);
if !columns_with_value.contains(&path) {
columns_with_value.push(path);
}
}
Err(e) => {
return Err(e);
}
}
}
output.push(Value::record(record, span))
} else {
output.push(input_val)
}
}
Ok(output
.into_iter()
.into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone()))
}
_ => {
if !columns.is_empty() {
let mut record = Record::new();
for cell_path in columns {
match v.clone().follow_cell_path(&cell_path.members, false) {
Ok(result) => {
record.push(cell_path.to_string().replace('.', "_"), result);
}
Err(e) => return Err(e),
}
}
Ok(Value::record(record, call_span)
.into_pipeline_data_with_metadata(metadata))
} else {
Ok(v.into_pipeline_data_with_metadata(metadata))
}
}
}
}
PipelineData::ListStream(stream, metadata, ..) => {
let mut values = vec![];
for x in stream {
if !columns.is_empty() {
let mut record = Record::new();
for path in &columns {
match x.clone().follow_cell_path(&path.members, false) {
Ok(value) => {
record.push(path.to_string().replace('.', "_"), value);
}
Err(e) => return Err(e),
}
}
values.push(Value::record(record, call_span));
} else {
values.push(x);
}
}
Ok(values.into_pipeline_data_with_metadata(metadata, engine_state.ctrlc.clone()))
}
_ => Ok(PipelineData::empty()),
}
}
struct NthIterator {
input: PipelineIterator,
rows: std::iter::Peekable<std::collections::btree_set::IntoIter<usize>>,
current: usize,
}
impl Iterator for NthIterator {
type Item = Value;
fn next(&mut self) -> Option<Self::Item> {
loop {
if let Some(row) = self.rows.peek() {
if self.current == *row {
self.rows.next();
self.current += 1;
return self.input.next();
} else {
self.current += 1;
let _ = self.input.next();
continue;
}
} else {
return None;
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Select)
}
}