narrative-macros 0.1.0

Procedural macros for the narrative crate
Documentation 
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use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::parse::{Parse, ParseStream};

use crate::step_attr_syntax::StepAttr;

pub struct StoryStep {
    pub attr: StepAttr,
    pub inner: syn::TraitItemFn,
}

impl Parse for StoryStep {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let attr = input.parse()?;
        let inner = input.parse()?;
        Ok(Self { attr, inner })
    }
}

impl ToTokens for StoryStep {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        self.attr.to_tokens(tokens);
        self.inner.to_tokens(tokens);
    }
}

impl StoryStep {
    pub(crate) fn attr_args(&self) -> impl Iterator<Item = (&syn::Ident, &syn::Expr)> {
        self.attr.args.iter().map(|arg| (&arg.ident, &arg.value))
    }

    /// This ignores patterns.
    pub(crate) fn fn_args(&self) -> impl Iterator<Item = (&syn::Ident, &syn::Type)> {
        self.inner
            .sig
            .inputs
            .iter()
            .filter_map(|input| match input {
                syn::FnArg::Typed(pat_type) => {
                    if let syn::Pat::Ident(pat_ident) = pat_type.pat.as_ref() {
                        Some((&pat_ident.ident, pat_type.ty.as_ref()))
                    } else {
                        None
                    }
                }
                syn::FnArg::Receiver(_) => None,
            })
    }

    pub(crate) fn find_attr_arg<'a>(&'a self, ident: &'a syn::Ident) -> Option<&'a syn::Expr> {
        self.attr_args().find_map(move |(arg_ident, arg_value)| {
            if arg_ident == ident {
                Some(arg_value)
            } else {
                None
            }
        })
    }
}

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

    #[test]
    fn parse_step() {
        let input = quote! {
            #[step("Step 1")]
            fn step1();
        };
        let actual = syn::parse2::<StoryStep>(input).unwrap();
        assert_eq!(actual.attr.text.value(), "Step 1".to_string());
        assert_eq!(actual.inner.sig.ident.to_string(), "step1".to_string());
    }

    #[test]
    fn to_tokens() {
        let input = quote! {
            #[step("Step 1")]
            fn step1();
        };
        let actual = syn::parse2::<StoryStep>(input).unwrap();
        let actual = quote! {
            #actual
        };
        let expected = quote! {
            #[step("Step 1")]
            fn step1();
        };
        assert_eq!(actual.to_string(), expected.to_string());
    }
}