vrl 0.32.0

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

fn unique(value: Value) -> Resolved {
    let value = value.try_array()?;
    let set: IndexSet<_> = value.into_iter().collect();
    Ok(set.into_iter().collect())
}

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

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

    fn usage(&self) -> &'static str {
        indoc! {"
            Returns the unique values for an array.

            The first occurrence of each element is kept.
        "}
    }

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

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

    fn examples(&self) -> &'static [Example] {
        &[example! {
            title: "Unique",
            source: r#"unique(["foo", "bar", "foo", "baz"])"#,
            result: Ok(r#"["foo", "bar", "baz"]"#),
        }]
    }

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

        Ok(UniqueFn { value }.as_expr())
    }

    fn parameters(&self) -> &'static [Parameter] {
        const PARAMETERS: &[Parameter] = &[Parameter::required(
            "value",
            kind::ARRAY,
            "The array to return unique elements from.",
        )];
        PARAMETERS
    }
}

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

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

    fn type_def(&self, _: &state::TypeState) -> TypeDef {
        TypeDef::array(Collection::any())
    }
}

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

    test_function![
        unique => Unique;

        default {
            args: func_args![
                value: value!(["bar", "foo", "baz", "foo"]),
            ],
            want: Ok(value!(["bar", "foo", "baz"])),
            tdef: TypeDef::array(Collection::any()),
        }

        mixed_values {
            args: func_args![
                value: value!(["foo", [1,2,3], "123abc", 1, true, [1,2,3], "foo", true, 1]),
            ],
            want: Ok(value!(["foo", [1,2,3], "123abc", 1, true])),
            tdef: TypeDef::array(Collection::any()),
        }
    ];
}