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getset 0.0.9

Getset, we're ready to go! A procedural macro for generating the most basic getters and setters on fields.
Documentation 
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use proc_macro2::TokenStream as TokenStream2;
use proc_macro2::{Ident, Span};
use syn::{self, Field, Lit, Meta, MetaNameValue, Visibility};

pub struct GenParams {
    pub attribute_name: &'static str,
    pub fn_name_prefix: &'static str,
    pub fn_name_suffix: &'static str,
    pub global_attr: Option<Meta>,
}

#[derive(PartialEq, Eq)]
pub enum GenMode {
    Get,
    GetCopy,
    Set,
    GetMut,
}

impl GenMode {
    fn is_get(&self) -> bool {
        match self {
            GenMode::Get | GenMode::GetCopy | GenMode::GetMut => true,
            GenMode::Set => false,
        }
    }
}

pub fn parse_visibility(attr: Option<&Meta>, meta_name: &str) -> Option<Visibility> {
    match attr {
        // `#[get = "pub"]` or `#[set = "pub"]`
        Some(Meta::NameValue(MetaNameValue {
            lit: Lit::Str(ref s),
            path,
            ..
        })) => {
            if path.is_ident(meta_name) {
                s.value()
                    .split(' ')
                    .find(|v| *v != "with_prefix")
                    .map(|v| syn::parse(v.parse().unwrap()).expect("invalid visibility found"))
            } else {
                None
            }
        }
        _ => None,
    }
}

/// Some users want legacy/compatability.
/// (Getters are often prefixed with `get_`)
fn has_prefix_attr(f: &Field) -> bool {
    let inner = f
        .attrs
        .iter()
        .filter_map(|v| {
            let meta = v.parse_meta().expect("Could not get attribute");
            if ["get", "get_copy"]
                .iter()
                .any(|ident| meta.path().is_ident(ident))
            {
                Some(meta)
            } else {
                None
            }
        })
        .last();
    match inner {
        Some(Meta::NameValue(meta)) => {
            if let Lit::Str(lit) = meta.lit {
                // Naive tokenization to avoid a possible visibility mod named `with_prefix`.
                lit.value().split(' ').any(|v| v == "with_prefix")
            } else {
                false
            }
        }
        _ => false,
    }
}

pub fn implement(field: &Field, mode: &GenMode, params: &GenParams) -> TokenStream2 {
    let field_name = field
        .clone()
        .ident
        .expect("Expected the field to have a name");

    let fn_name = Ident::new(
        &format!(
            "{}{}{}{}",
            if has_prefix_attr(field) && (mode.is_get()) {
                "get_"
            } else {
                ""
            },
            params.fn_name_prefix,
            field_name,
            params.fn_name_suffix
        ),
        Span::call_site(),
    );
    let ty = field.ty.clone();

    let mut doc = Vec::new();
    let attr = field
        .attrs
        .iter()
        .filter_map(|v| {
            let meta = v.parse_meta().expect("attribute");
            if meta.path().is_ident("doc") {
                doc.push(v);
                None
            } else if meta.path().is_ident(params.attribute_name) {
                Some(meta)
            } else {
                None
            }
        })
        .last()
        .or_else(|| params.global_attr.clone());

    let visibility = parse_visibility(attr.as_ref(), params.attribute_name);
    match attr {
        Some(_) => match mode {
            GenMode::Get => {
                quote! {
                    #(#doc)*
                    #[inline(always)]
                    #visibility fn #fn_name(&self) -> &#ty {
                        &self.#field_name
                    }
                }
            }
            GenMode::GetCopy => {
                quote! {
                    #(#doc)*
                    #[inline(always)]
                    #visibility fn #fn_name(&self) -> #ty {
                        self.#field_name
                    }
                }
            }
            GenMode::Set => {
                quote! {
                    #(#doc)*
                    #[inline(always)]
                    #visibility fn #fn_name(&mut self, val: #ty) -> &mut Self {
                        self.#field_name = val;
                        self
                    }
                }
            }
            GenMode::GetMut => {
                quote! {
                    #(#doc)*
                    #[inline(always)]
                    #visibility fn #fn_name(&mut self) -> &mut #ty {
                        &mut self.#field_name
                    }
                }
            }
        },
        // Don't need to do anything.
        None => quote! {},
    }
}