nu_cmd_lang/core_commands/
const_.rs

1use nu_engine::command_prelude::*;
2use nu_protocol::engine::CommandType;
3
4#[derive(Clone)]
5pub struct Const;
6
7impl Command for Const {
8    fn name(&self) -> &str {
9        "const"
10    }
11
12    fn description(&self) -> &str {
13        "Create a parse-time constant."
14    }
15
16    fn signature(&self) -> nu_protocol::Signature {
17        Signature::build("const")
18            .input_output_types(vec![(Type::Nothing, Type::Nothing)])
19            .allow_variants_without_examples(true)
20            .required(
21                "const_name",
22                SyntaxShape::VarWithOptType,
23                "The constant name to create.",
24            )
25            .required(
26                "initial_value",
27                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::MathExpression)),
28                "Equals sign followed by constant value.",
29            )
30            .category(Category::Core)
31    }
32
33    fn extra_description(&self) -> &str {
34        r#"This command is a parser keyword. For details, check:
35  https://www.nushell.sh/book/thinking_in_nu.html"#
36    }
37
38    fn command_type(&self) -> CommandType {
39        CommandType::Keyword
40    }
41
42    fn search_terms(&self) -> Vec<&str> {
43        vec!["set", "let"]
44    }
45
46    fn run(
47        &self,
48        _engine_state: &EngineState,
49        _stack: &mut Stack,
50        _call: &Call,
51        _input: PipelineData,
52    ) -> Result<PipelineData, ShellError> {
53        // This is compiled specially by the IR compiler. The code here is never used when
54        // running in IR mode.
55        eprintln!(
56            "Tried to execute 'run' for the 'const' command: this code path should never be reached in IR mode"
57        );
58        unreachable!()
59    }
60
61    fn run_const(
62        &self,
63        _working_set: &StateWorkingSet,
64        _call: &Call,
65        _input: PipelineData,
66    ) -> Result<PipelineData, ShellError> {
67        Ok(PipelineData::empty())
68    }
69
70    fn is_const(&self) -> bool {
71        true
72    }
73
74    fn examples(&self) -> Vec<Example<'_>> {
75        vec![
76            Example {
77                description: "Create a new parse-time constant.",
78                example: "const x = 10",
79                result: None,
80            },
81            Example {
82                description: "Create a composite constant value.",
83                example: "const x = { a: 10, b: 20 }",
84                result: None,
85            },
86        ]
87    }
88}
89
90#[cfg(test)]
91mod test {
92    use nu_protocol::engine::CommandType;
93
94    use super::*;
95
96    #[test]
97    fn test_examples() {
98        use crate::test_examples;
99
100        test_examples(Const {})
101    }
102
103    #[test]
104    fn test_command_type() {
105        assert!(matches!(Const.command_type(), CommandType::Keyword));
106    }
107}
nu_cmd_lang/core_commands/const_.rs

nu_cmd_lang/core_commands/
const_.rs
