fieldx_aux 0.1.14

Various types and tools useful for fieldx crates and, potentially, to users of fieldx
Documentation 
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//! The most basic helper declaration

use crate::set_literals;
use crate::FXAttributes;
use crate::FXBool;
use crate::FXOrig;
use crate::FXProp;
use crate::FXPropBool;
use crate::FXSetState;
use crate::FXString;
use crate::FXTryInto;
use crate::FromNestAttr;

use darling::util::Flag;
use darling::FromMeta;
use fieldx_derive_support::fxhelper;
use getset::Getters;
use proc_macro2::TokenStream;
use syn::Lit;

/// Minimal helper declaration. For example, `fieldx` uses it for helpers like `reader` or `writer`.
///
/// The `BOOL_ONLY` parameter disables the literal subargument that specifies custom helper name. For example, with
/// the following declaraion, argument `foo("my_name")` results in an error:
///
/// ```ignore
///     foo: FXNestingAttr<FXBaseHelper<true>>,
/// ```
#[fxhelper(to_tokens)]
#[derive(Default, Debug)]
pub struct FXBaseHelper<const BOOL_ONLY: bool = false> {}

impl<const BOOL_ONLY: bool> FXBaseHelper<BOOL_ONLY> {
    fn allowed_literals(&self, literals: &Vec<Lit>) -> darling::Result<()> {
        if BOOL_ONLY {
            return Err(self.no_literals(literals).unwrap_err());
        }
        Ok(())
    }
}

impl<const BOOL_ONLY: bool> FromNestAttr for FXBaseHelper<BOOL_ONLY> {
    set_literals! {helper, ..1usize => name; pre_validate => allowed_literals}

    fn for_keyword(_path: &syn::Path) -> darling::Result<Self> {
        Ok(Self::default())
    }
}

impl<const BOOL_ONLY: bool> From<FXBaseHelper<BOOL_ONLY>> for bool {
    fn from(value: FXBaseHelper<BOOL_ONLY>) -> Self {
        *value.is_set()
    }
}

impl<const BOOL_ONLY: bool> From<&FXBaseHelper<BOOL_ONLY>> for bool {
    fn from(value: &FXBaseHelper<BOOL_ONLY>) -> Self {
        *value.is_set()
    }
}

impl<const BOOL_ONLY: bool> From<bool> for FXBaseHelper<BOOL_ONLY> {
    fn from(value: bool) -> Self {
        Self {
            off: Flag::from(value),
            ..Default::default()
        }
    }
}