vrl 0.32.0

Vector Remap Language
Documentation 
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use crate::compiler::prelude::*;
use tracing::warn;

fn to_regex(value: &Value) -> Resolved {
    let string = value.try_bytes_utf8_lossy()?;
    let regex = regex::Regex::new(string.as_ref())
        .map_err(|err| format!("could not create regex: {err}"))
        .map(Into::into)?;
    Ok(regex)
}

#[derive(Clone, Copy, Debug)]
pub struct ToRegex;

impl Function for ToRegex {
    fn identifier(&self) -> &'static str {
        "to_regex"
    }

    fn usage(&self) -> &'static str {
        "Coerces the `value` into a regex."
    }

    fn category(&self) -> &'static str {
        Category::Coerce.as_ref()
    }

    fn internal_failure_reasons(&self) -> &'static [&'static str] {
        &["`value` is not a string."]
    }

    fn return_kind(&self) -> u16 {
        kind::REGEX
    }

    fn return_rules(&self) -> &'static [&'static str] {
        &[
            "If `value` is a string that contains a valid regex, returns the regex constructed with this string.",
        ]
    }

    fn notices(&self) -> &'static [&'static str] {
        &[indoc! {"
            Compiling a regular expression is an expensive operation and can limit Vector's
            throughput. Don't use this function unless you are absolutely sure there is no other
            way!
        "}]
    }

    fn parameters(&self) -> &'static [Parameter] {
        const PARAMETERS: &[Parameter] = &[Parameter::required(
            "value",
            kind::BYTES,
            "The value to convert to a regex.",
        )];
        PARAMETERS
    }

    fn examples(&self) -> &'static [Example] {
        &[example! {
            title: "Coerce to a regex",
            source: r#"to_regex!("^foo$")"#,
            result: Ok("r'^foo$'"),
        }]
    }

    fn compile(
        &self,
        _state: &state::TypeState,
        _ctx: &mut FunctionCompileContext,
        arguments: ArgumentList,
    ) -> Compiled {
        warn!("`to_regex` is an expensive function that could impact throughput.");
        let value = arguments.required("value");
        Ok(ToRegexFn { value }.as_expr())
    }
}

#[derive(Debug, Clone)]
struct ToRegexFn {
    value: Box<dyn Expression>,
}

impl FunctionExpression for ToRegexFn {
    fn resolve(&self, ctx: &mut Context) -> Resolved {
        let value = self.value.resolve(ctx)?;
        to_regex(&value)
    }

    fn type_def(&self, _: &state::TypeState) -> TypeDef {
        TypeDef::regex().fallible()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    test_function![
        to_regex => ToRegex;

        regex {
            args: func_args![value: "^test[A-Za-z_]+$"],
            want: Ok(regex::Regex::new("^test[A-Za-z_]+$").expect("regex is valid")),
            tdef: TypeDef::regex().fallible(),
        }

        invalid_regex {
            args: func_args![value: "(+)"],
            want: Err("could not create regex: regex parse error:\n    (+)\n     ^\nerror: repetition operator missing expression"),
            tdef: TypeDef::regex().fallible(),
        }
    ];
}