nu_cmd_lang/core_commands/
mut_.rs

1use nu_engine::command_prelude::*;
2use nu_protocol::engine::CommandType;
3
4#[derive(Clone)]
5pub struct Mut;
6
7impl Command for Mut {
8    fn name(&self) -> &str {
9        "mut"
10    }
11
12    fn description(&self) -> &str {
13        "Create a mutable variable and give it a value."
14    }
15
16    fn signature(&self) -> nu_protocol::Signature {
17        Signature::build("mut")
18            .input_output_types(vec![(Type::Any, Type::Nothing)])
19            .allow_variants_without_examples(true)
20            .required("var_name", SyntaxShape::VarWithOptType, "Variable name.")
21            .required(
22                "initial_value",
23                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::MathExpression)),
24                "Equals sign followed by value.",
25            )
26            .category(Category::Core)
27    }
28
29    fn extra_description(&self) -> &str {
30        r#"This command is a parser keyword. For details, check:
31  https://www.nushell.sh/book/thinking_in_nu.html"#
32    }
33
34    fn command_type(&self) -> CommandType {
35        CommandType::Keyword
36    }
37
38    fn search_terms(&self) -> Vec<&str> {
39        vec!["set", "mutable"]
40    }
41
42    fn run(
43        &self,
44        _engine_state: &EngineState,
45        _stack: &mut Stack,
46        _call: &Call,
47        _input: PipelineData,
48    ) -> Result<PipelineData, ShellError> {
49        // This is compiled specially by the IR compiler. The code here is never used when
50        // running in IR mode.
51        eprintln!(
52            "Tried to execute 'run' for the 'mut' command: this code path should never be reached in IR mode"
53        );
54        unreachable!()
55    }
56
57    fn examples(&self) -> Vec<Example<'_>> {
58        vec![
59            Example {
60                description: "Set a mutable variable to a value, then update it",
61                example: "mut x = 10; $x = 12",
62                result: None,
63            },
64            Example {
65                description: "Upsert a value inside a mutable data structure",
66                example: "mut a = {b:{c:1}}; $a.b.c = 2",
67                result: None,
68            },
69            Example {
70                description: "Set a mutable variable to the result of an expression",
71                example: "mut x = 10 + 100",
72                result: None,
73            },
74            Example {
75                description: "Set a mutable variable based on the condition",
76                example: "mut x = if false { -1 } else { 1 }",
77                result: None,
78            },
79        ]
80    }
81}
82
83#[cfg(test)]
84mod test {
85    use nu_protocol::engine::CommandType;
86
87    use super::*;
88
89    #[test]
90    fn test_examples() {
91        use crate::test_examples;
92
93        test_examples(Mut {})
94    }
95
96    #[test]
97    fn test_command_type() {
98        assert!(matches!(Mut.command_type(), CommandType::Keyword));
99    }
100}
nu_cmd_lang/core_commands/mut_.rs

nu_cmd_lang/core_commands/
mut_.rs
