darling 0.24.1

A proc-macro library for reading attributes into structs when implementing custom derives.
Documentation
//! Test that skipped fields are not read into structs when they appear in input.

use std::assert_eq;

use darling::{FromDeriveInput, FromMeta};
use syn::parse_quote;

#[derive(Debug, PartialEq, Eq, FromDeriveInput)]
#[darling(attributes(skip_test))]
pub struct Lorem {
    ipsum: String,

    #[darling(skip)]
    dolor: u8,
}

/// Verify variant-level and field-level skip work correctly for enums.
#[derive(Debug, FromMeta)]
pub enum Sit {
    Amet(bool),

    #[darling(skip)]
    Foo {
        hello: bool,
    },

    Bar {
        hello: bool,
        #[darling(skip)]
        world: u8,
    },
}

#[test]
fn verify_skipped_field_not_required() {
    let di = parse_quote! {
        #[skip_test(ipsum = "Hello")]
        struct Baz;
    };

    assert_eq!(
        Lorem::from_derive_input(&di).unwrap(),
        Lorem {
            ipsum: "Hello".to_string(),
            dolor: 0,
        }
    );
}

/// This test verifies that a skipped field will still prefer an explicit default
/// over the default that would come from its field type. It would be incorrect for
/// `Defaulting::from_derive_input` to fail here, and it would be wrong for the value
/// of `dolor` to be `None`.
#[test]
fn verify_default_supersedes_from_none() {
    fn default_dolor() -> Option<u8> {
        Some(2)
    }

    #[derive(Debug, PartialEq, Eq, FromDeriveInput)]
    #[darling(attributes(skip_test))]
    pub struct Defaulting {
        #[darling(skip, default = "default_dolor")]
        dolor: Option<u8>,
    }

    let di = parse_quote! {
        #[skip_test]
        struct Baz;
    };

    assert_eq!(
        Defaulting::from_derive_input(&di).unwrap(),
        Defaulting { dolor: Some(2) }
    )
}

/// Verify skipping a variant also excludes that from "did you mean" suggestions.
#[derive(Debug, FromMeta)]
pub enum SkippedVariant {
    Foo,
    #[darling(skip)]
    Boo,
}

#[test]
fn skipped_variants_are_not_suggested() {
    let err_msg = SkippedVariant::from_string("boo")
        .expect_err("boo variant is not constructable by FromMeta")
        .to_string();

    // If `boo` was improperly considered for "did-you-mean", it will be the top match.
    // At time of writing, only the top candidate was included in the error, so we check
    // that the second-place suggestion was present in the message, and try to defend against
    // a multi-suggestion future by also checking that `boo` only appears once in the error.
    assert_eq!(
        err_msg.split("`boo`").count(),
        2,
        "error message contained `boo` too many times, was: {err_msg}"
    );

    assert!(
        err_msg.contains("`foo`"),
        "error message did not suggest `foo`, was actually: {err_msg}",
    );
}