1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187

use super::utils::chain_error_with_input;
use nu_engine::{command_prelude::*, ClosureEval, ClosureEvalOnce};
use nu_protocol::engine::Closure;

#[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 head = call.head;
        let closure: Closure = call.req(engine_state, stack, 0)?;

        let metadata = input.metadata();
        match input {
            PipelineData::Empty => Ok(PipelineData::Empty),
            PipelineData::Value(Value::Range { .. }, ..)
            | PipelineData::Value(Value::List { .. }, ..)
            | PipelineData::ListStream(..) => {
                let mut closure = ClosureEval::new(engine_state, stack, closure);
                Ok(input
                    .into_iter()
                    .filter_map(move |value| {
                        match closure
                            .run_with_value(value.clone())
                            .and_then(|data| data.into_value(head))
                        {
                            Ok(cond) => cond.is_true().then_some(value),
                            Err(err) => {
                                let span = value.span();
                                let err = chain_error_with_input(err, value.is_error(), span);
                                Some(Value::error(err, span))
                            }
                        }
                    })
                    .into_pipeline_data(head, engine_state.signals().clone()))
            }
            PipelineData::ByteStream(stream, ..) => {
                if let Some(chunks) = stream.chunks() {
                    let mut closure = ClosureEval::new(engine_state, stack, closure);
                    Ok(chunks
                        .into_iter()
                        .filter_map(move |value| {
                            let value = match value {
                                Ok(value) => value,
                                Err(err) => return Some(Value::error(err, head)),
                            };

                            match closure
                                .run_with_value(value.clone())
                                .and_then(|data| data.into_value(head))
                            {
                                Ok(cond) => cond.is_true().then_some(value),
                                Err(err) => {
                                    let span = value.span();
                                    let err = chain_error_with_input(err, value.is_error(), span);
                                    Some(Value::error(err, span))
                                }
                            }
                        })
                        .into_pipeline_data(head, engine_state.signals().clone()))
                } else {
                    Ok(PipelineData::Empty)
                }
            }
            // This match allows non-iterables to be accepted,
            // which is currently considered undesirable (Nov 2022).
            PipelineData::Value(value, ..) => {
                let result = ClosureEvalOnce::new(engine_state, stack, closure)
                    .run_with_value(value.clone())
                    .and_then(|data| data.into_value(head));

                Ok(match result {
                    Ok(cond) => cond.is_true().then_some(value),
                    Err(err) => {
                        let span = value.span();
                        let err = chain_error_with_input(err, value.is_error(), span);
                        Some(Value::error(err, span))
                    }
                }
                .into_pipeline_data(head, engine_state.signals().clone()))
            }
        }
        .map(|data| data.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 {})
    }
}