vrl 0.32.0

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

fn keys(value: Value) -> Resolved {
    let object = value.try_object()?;
    let keys = object.into_keys().map(Value::from);
    Ok(Value::Array(keys.collect()))
}

#[derive(Debug)]
pub struct Keys;

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

    fn usage(&self) -> &'static str {
        "Returns the keys from the object passed into the function."
    }

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

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

    fn return_rules(&self) -> &'static [&'static str] {
        &["Returns an array of all the keys"]
    }

    fn parameters(&self) -> &'static [Parameter] {
        const PARAMETERS: &[Parameter] = &[Parameter::required(
            "value",
            kind::OBJECT,
            "The object to extract keys from.",
        )];
        PARAMETERS
    }

    fn examples(&self) -> &'static [Example] {
        &[example! {
            title: "Get keys from the object",
            source: indoc! {r#"
                keys({
                    "key1": "val1",
                    "key2": "val2"
                })
            "#},
            result: Ok(r#"["key1", "key2"]"#),
        }]
    }

    fn compile(
        &self,
        _state: &TypeState,
        _ctx: &mut FunctionCompileContext,
        arguments: ArgumentList,
    ) -> Compiled {
        let value = arguments.required("value");
        Ok(KeysFn { value }.as_expr())
    }
}

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

impl FunctionExpression for KeysFn {
    fn resolve(&self, ctx: &mut Context) -> Resolved {
        keys(self.value.resolve(ctx)?)
    }

    fn type_def(&self, _state: &state::TypeState) -> TypeDef {
        TypeDef::array(Collection::empty().with_unknown(Kind::bytes())).infallible()
    }
}