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use super::utils::chain_error_with_input;
use nu_engine::{eval_block, CallExt};
use nu_protocol::ast::Call;
use nu_protocol::engine::{Closure, Command, EngineState, Stack};
use nu_protocol::{
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
ShellError, Signature, SyntaxShape, Type, Value,
};
#[derive(Clone)]
pub struct Filter;
impl Command for Filter {
fn name(&self) -> &str {
"filter"
}
fn usage(&self) -> &str {
"Filter values based on a predicate closure."
}
fn extra_usage(&self) -> &str {
r#"This command works similar to 'where' but allows reading the predicate closure from
a variable. On the other hand, the "row condition" syntax is not supported."#
}
fn signature(&self) -> nu_protocol::Signature {
Signature::build("filter")
.input_output_types(vec![
(
Type::List(Box::new(Type::Any)),
Type::List(Box::new(Type::Any)),
),
(Type::Range, Type::List(Box::new(Type::Any))),
])
.required(
"closure",
SyntaxShape::Closure(Some(vec![SyntaxShape::Any, SyntaxShape::Int])),
"Predicate closure.",
)
.category(Category::Filters)
}
fn search_terms(&self) -> Vec<&str> {
vec!["where", "find", "search", "condition"]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let capture_block: Closure = call.req(engine_state, stack, 0)?;
let metadata = input.metadata();
let ctrlc = engine_state.ctrlc.clone();
let engine_state = engine_state.clone();
let block = engine_state.get_block(capture_block.block_id).clone();
let mut stack = stack.captures_to_stack(capture_block.captures);
let orig_env_vars = stack.env_vars.clone();
let orig_env_hidden = stack.env_hidden.clone();
let span = call.head;
let redirect_stdout = call.redirect_stdout;
let redirect_stderr = call.redirect_stderr;
match input {
PipelineData::Empty => Ok(PipelineData::Empty),
PipelineData::Value(Value::Range { .. }, ..)
| PipelineData::Value(Value::List { .. }, ..)
| PipelineData::ListStream { .. } => Ok(input
// To enumerate over the input (for the index argument),
// it must be converted into an iterator using into_iter().
.into_iter()
.filter_map(move |x| {
// with_env() is used here to ensure that each iteration uses
// a different set of environment variables.
// Hence, a 'cd' in the first loop won't affect the next loop.
stack.with_env(&orig_env_vars, &orig_env_hidden);
if let Some(var) = block.signature.get_positional(0) {
if let Some(var_id) = &var.var_id {
stack.add_var(*var_id, x.clone());
}
}
match eval_block(
&engine_state,
&mut stack,
&block,
// clone() is used here because x is given to Ok() below.
x.clone().into_pipeline_data(),
redirect_stdout,
redirect_stderr,
) {
Ok(v) => {
if v.into_value(span).is_true() {
Some(x)
} else {
None
}
}
Err(error) => Some(Value::error(
chain_error_with_input(error, x.is_error(), x.span()),
x.span(),
)),
}
})
.into_pipeline_data(ctrlc)),
PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
PipelineData::ExternalStream {
stdout: Some(stream),
..
} => Ok(stream
.into_iter()
.filter_map(move |x| {
// see note above about with_env()
stack.with_env(&orig_env_vars, &orig_env_hidden);
let x = match x {
Ok(x) => x,
Err(err) => return Some(Value::error(err, span)),
};
if let Some(var) = block.signature.get_positional(0) {
if let Some(var_id) = &var.var_id {
stack.add_var(*var_id, x.clone());
}
}
match eval_block(
&engine_state,
&mut stack,
&block,
// clone() is used here because x is given to Ok() below.
x.clone().into_pipeline_data(),
redirect_stdout,
redirect_stderr,
) {
Ok(v) => {
if v.into_value(span).is_true() {
Some(x)
} else {
None
}
}
Err(error) => Some(Value::error(
chain_error_with_input(error, x.is_error(), x.span()),
x.span(),
)),
}
})
.into_pipeline_data(ctrlc)),
// This match allows non-iterables to be accepted,
// which is currently considered undesirable (Nov 2022).
PipelineData::Value(x, ..) => {
// see note above about with_env()
stack.with_env(&orig_env_vars, &orig_env_hidden);
if let Some(var) = block.signature.get_positional(0) {
if let Some(var_id) = &var.var_id {
stack.add_var(*var_id, x.clone());
}
}
Ok(match eval_block(
&engine_state,
&mut stack,
&block,
// clone() is used here because x is given to Ok() below.
x.clone().into_pipeline_data(),
redirect_stdout,
redirect_stderr,
) {
Ok(v) => {
if v.into_value(span).is_true() {
Some(x)
} else {
None
}
}
Err(error) => Some(Value::error(
chain_error_with_input(error, x.is_error(), x.span()),
x.span(),
)),
}
.into_pipeline_data(ctrlc))
}
}
.map(|x| x.set_metadata(metadata))
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "Filter items of a list according to a condition",
example: "[1 2] | filter {|x| $x > 1}",
result: Some(Value::test_list(vec![Value::test_int(2)])),
},
Example {
description: "Filter rows of a table according to a condition",
example: "[{a: 1} {a: 2}] | filter {|x| $x.a > 1}",
result: Some(Value::test_list(vec![Value::test_record(record! {
"a" => Value::test_int(2),
})])),
},
Example {
description: "Filter rows of a table according to a stored condition",
example: "let cond = {|x| $x.a > 1}; [{a: 1} {a: 2}] | filter $cond",
result: Some(Value::test_list(vec![Value::test_record(record! {
"a" => Value::test_int(2),
})])),
},
Example {
description: "Filter items of a range according to a condition",
example: "9..13 | filter {|el| $el mod 2 != 0}",
result: Some(Value::test_list(vec![
Value::test_int(9),
Value::test_int(11),
Value::test_int(13),
])),
},
Example {
description: "List all numbers above 3, using an existing closure condition",
example: "let a = {$in > 3}; [1, 2, 5, 6] | filter $a",
result: None, // TODO: This should work
// result: Some(Value::test_list(
// vec![
// Value::Int {
// val: 5,
// Span::test_data(),
// },
// Value::Int {
// val: 6,
// span: Span::test_data(),
// },
// ],
// }),
},
]
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(Filter {})
}
}