fieldx 0.2.3

Procedural macro for constructing structs with lazily initialized fields, builder pattern, and serde support with a focus on declarative syntax.
Documentation 
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#![allow(clippy::approx_constant)]
// With this `deny` we make sure that attributes_impl is actually applied.
#![deny(dead_code)]
use fieldx::fxstruct;

#[fxstruct(
    builder(vis(pub(crate)), attributes(derive(Debug))),
    attributes_impl(allow(dead_code))
)]
#[derive(Debug)]
struct Plain {
    #[fieldx(lazy, clearer, predicate, rename("dummy"))]
    foo:    String,
    #[fieldx(lazy, vis(), predicate, clearer, set, builder(attributes_fn(allow(dead_code))))]
    bar:    i32,
    #[fieldx(default(3.1415926))]
    pub pi: f32,

    // Let's try a charged but not lazy field
    #[fieldx(
        clearer,
        predicate,
        get,
        set,
        default("bazzification".to_string()),
        builder(attributes_fn(allow(dead_code)))
    )]
    baz: String,

    #[fieldx(clearer, predicate, get, set)]
    fubar: f32,

    #[fieldx(lazy, clearer, default(Self::default_string()))]
    lazy_default: String,

    #[fieldx(inner_mut, set, get, into)]
    modifiable: String,

    #[fieldx(optional, get, default("all good".to_string()))]
    optional_default: String,
}

impl Plain {
    fn build_dummy(&self) -> String {
        format!("this is foo with bar={}", self.bar()).to_string()
    }

    fn build_bar(&self) -> i32 {
        42
    }

    fn build_lazy_default(&self) -> String {
        "this is a lazy default".into()
    }

    fn default_string() -> String {
        "this is default string value".to_string()
    }
}

#[test]
fn basic() {
    let mut plain = Plain::builder()
        .dummy("as banal as it gets".into())
        .pi(-1.2)
        .modifiable("from builder")
        .build()
        .expect("Plain instance");

    assert_eq!(plain.pi, -1.2, "pi set manually");
    assert_eq!(
        plain.clear_dummy(),
        Some("as banal as it gets".to_string()),
        "foo(dummy) was set manually"
    );
    assert_eq!(
        plain.dummy(),
        &"this is foo with bar=42".to_string(),
        "foo(dummy) was lazily set"
    );
    assert_eq!(
        plain.baz(),
        &Some("bazzification".to_string()),
        "baz is set with its default by the builder"
    );
    assert_eq!(plain.fubar(), &None, "fubar has no default and was not set");
    assert_eq!(*plain.modifiable(), "from builder".to_string());

    assert_eq!(
        plain.lazy_default(),
        "this is default string value",
        "lazy field gets a default if not set"
    );

    assert_eq!(
        plain.optional_default(),
        &Some("all good".to_string()),
        "optional field gets a default if not set"
    );

    let mut plain = Plain::builder()
        .lazy_default("non-lazy, non-default".to_string())
        .modifiable("from builder".to_string())
        .build()
        .expect("Plain instance");
    assert_eq!(
        plain.lazy_default(),
        "non-lazy, non-default",
        "lazy field set manually, default is ignored"
    );
    plain.clear_lazy_default();
    assert_eq!(
        plain.lazy_default(),
        "this is a lazy default",
        "lazy field gets set by its builder when cleared"
    );

    let old = plain.set_modifiable("set manually");
    assert_eq!(old, "from builder");
    assert_eq!(*plain.modifiable(), "set manually".to_string());
}