vrl 0.32.0

Vector Remap Language
Documentation 
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use crate::compiler::prelude::{TypeDef as VrlTypeDef, *};

fn type_def(type_def: &VrlTypeDef) -> Value {
    let mut tree = type_def.kind().canonicalize().debug_info();

    if type_def.is_fallible() {
        tree.insert("fallible".to_owned().into(), true.into());
    }

    tree.into()
}

/// A debug function to print the type definition of an expression at runtime.
///
/// This function is *UNDOCUMENTED* and *UNSTABLE*. It is *NOT* to be advertised
/// to users of Vector, even though it is technically usable by others.
#[derive(Clone, Copy, Debug)]
pub struct TypeDef;

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

    fn usage(&self) -> &'static str {
        indoc! {"
            Returns the type definition of an expression at runtime.

            This is a debug function that is *UNSTABLE*. Behavior is *NOT* guaranteed even though it is technically usable.
        "}
    }

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

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

    fn parameters(&self) -> &'static [Parameter] {
        const PARAMETERS: &[Parameter] = &[Parameter::required(
            "value",
            kind::ANY,
            "The expression to get the type definition for.",
        )];
        PARAMETERS
    }

    fn examples(&self) -> &'static [Example] {
        &[example! {
            title: "return type definition",
            source: "type_def(42)",
            result: Ok(r#"{ "integer": true }"#),
        }]
    }

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

#[derive(Debug, Clone)]
struct TypeDefFn {
    type_def: VrlTypeDef,
}

impl FunctionExpression for TypeDefFn {
    fn resolve(&self, _ctx: &mut Context) -> Resolved {
        Ok(type_def(&self.type_def.clone()))
    }

    fn type_def(&self, _state: &state::TypeState) -> VrlTypeDef {
        VrlTypeDef::any()
    }
}