vrl/stdlib/
to_string.rs

1use crate::compiler::prelude::*;
2
3fn to_string(value: Value) -> Resolved {
4    use Value::{Boolean, Bytes, Float, Integer, Null, Timestamp};
5    use chrono::SecondsFormat;
6    let value = match value {
7        v @ Bytes(_) => v,
8        Integer(v) => v.to_string().into(),
9        Float(v) => v.to_string().into(),
10        Boolean(v) => v.to_string().into(),
11        Timestamp(v) => v.to_rfc3339_opts(SecondsFormat::AutoSi, true).into(),
12        Null => "".into(),
13        v => return Err(format!("unable to coerce {} into string", v.kind()).into()),
14    };
15    Ok(value)
16}
17
18#[derive(Clone, Copy, Debug)]
19pub struct ToString;
20
21impl Function for ToString {
22    fn identifier(&self) -> &'static str {
23        "to_string"
24    }
25
26    fn usage(&self) -> &'static str {
27        "Coerces the `value` into a string."
28    }
29
30    fn category(&self) -> &'static str {
31        Category::Coerce.as_ref()
32    }
33
34    fn internal_failure_reasons(&self) -> &'static [&'static str] {
35        &["`value` is not an integer, float, boolean, string, timestamp, or null."]
36    }
37
38    fn return_kind(&self) -> u16 {
39        kind::BYTES
40    }
41
42    fn return_rules(&self) -> &'static [&'static str] {
43        &[
44            "If `value` is an integer or float, returns the string representation.",
45            "If `value` is a boolean, returns `\"true\"` or `\"false\"`.",
46            "If `value` is a timestamp, returns an [RFC 3339](\\(urls.rfc3339)) representation.",
47            "If `value` is a null, returns `\"\"`.",
48        ]
49    }
50
51    fn parameters(&self) -> &'static [Parameter] {
52        const PARAMETERS: &[Parameter] = &[Parameter::required(
53            "value",
54            kind::ANY,
55            "The value to convert to a string.",
56        )];
57        PARAMETERS
58    }
59
60    fn examples(&self) -> &'static [Example] {
61        &[
62            example! {
63                title: "Coerce to a string (Boolean)",
64                source: "to_string(true)",
65                result: Ok("s'true'"),
66            },
67            example! {
68                title: "Coerce to a string (int)",
69                source: "to_string(52)",
70                result: Ok("s'52'"),
71            },
72            example! {
73                title: "Coerce to a string (float)",
74                source: "to_string(52.2)",
75                result: Ok("s'52.2'"),
76            },
77            example! {
78                title: "String",
79                source: "to_string(s'foo')",
80                result: Ok("foo"),
81            },
82            example! {
83                title: "False",
84                source: "to_string(false)",
85                result: Ok("s'false'"),
86            },
87            example! {
88                title: "Null",
89                source: "to_string(null)",
90                result: Ok(""),
91            },
92            example! {
93                title: "Timestamp",
94                source: "to_string(t'2020-01-01T00:00:00Z')",
95                result: Ok("2020-01-01T00:00:00Z"),
96            },
97            example! {
98                title: "Array",
99                source: "to_string!([])",
100                result: Err(
101                    r#"function call error for "to_string" at (0:14): unable to coerce array into string"#,
102                ),
103            },
104            example! {
105                title: "Object",
106                source: "to_string!({})",
107                result: Err(
108                    r#"function call error for "to_string" at (0:14): unable to coerce object into string"#,
109                ),
110            },
111            example! {
112                title: "Regex",
113                source: "to_string!(r'foo')",
114                result: Err(
115                    r#"function call error for "to_string" at (0:18): unable to coerce regex into string"#,
116                ),
117            },
118        ]
119    }
120
121    fn compile(
122        &self,
123        _state: &state::TypeState,
124        _ctx: &mut FunctionCompileContext,
125        arguments: ArgumentList,
126    ) -> Compiled {
127        let value = arguments.required("value");
128
129        Ok(ToStringFn { value }.as_expr())
130    }
131}
132
133#[derive(Debug, Clone)]
134struct ToStringFn {
135    value: Box<dyn Expression>,
136}
137
138impl FunctionExpression for ToStringFn {
139    fn resolve(&self, ctx: &mut Context) -> Resolved {
140        let value = self.value.resolve(ctx)?;
141
142        to_string(value)
143    }
144
145    fn type_def(&self, state: &state::TypeState) -> TypeDef {
146        let td = self.value.type_def(state);
147
148        TypeDef::bytes()
149            .maybe_fallible(td.contains_array() || td.contains_object() || td.contains_regex())
150    }
151}
152
153#[cfg(test)]
154mod tests {
155    use super::*;
156
157    test_function![
158        to_string => ToString;
159
160        integer {
161            args: func_args![value: 20],
162            want: Ok("20"),
163            tdef: TypeDef::bytes(),
164        }
165
166        float {
167            args: func_args![value: 20.5],
168            want: Ok("20.5"),
169            tdef: TypeDef::bytes(),
170        }
171    ];
172}
vrl/stdlib/to_string.rs

vrl/stdlib/
to_string.rs
