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extern crate proc_macro; use proc_macro::TokenStream; use proc_macro2::Ident; use proc_macro2::{Group, TokenStream as TokenStream2}; use proc_macro_error::abort_call_site; use proc_macro_error::proc_macro_error; use quote::quote; use std::collections::HashMap; use syn::parse::{Parse, ParseStream}; use syn::punctuated::Punctuated; use syn::{ parse_macro_input, parse_quote, Attribute, Data, DataEnum, DataStruct, DeriveInput, Expr, Fields, FieldsNamed, Type, }; use syn::{FieldsUnnamed, Token, Variant}; #[derive(Default)] struct DialogueDefs { map: HashMap<String, Expr>, } struct DialogueDef { key: Ident, value: Expr, } #[derive(Default)] struct DialogueDefsParenthesized { inner: DialogueDefs, } struct ExtraConfig { prompt: Option<Expr>, name: Option<Expr>, } impl Parse for DialogueDef { fn parse(input: ParseStream) -> syn::Result<Self> { let key: Ident = input.parse()?; let _: Token![=] = input.parse()?; let value: Expr = input.parse()?; Ok(DialogueDef { key, value }) } } impl Parse for DialogueDefs { fn parse(input: ParseStream) -> syn::Result<Self> { let items: Punctuated<DialogueDef, Token![,]> = Punctuated::parse_terminated(input)?; let map = items .into_iter() .map(|dd| (dd.key.to_string(), dd.value)) .collect(); Ok(DialogueDefs { map }) } } impl Parse for DialogueDefsParenthesized { fn parse(input: ParseStream) -> syn::Result<Self> { let group: Group = input.parse()?; let defs: DialogueDefs = syn::parse2(group.stream())?; Ok(DialogueDefsParenthesized { inner: defs }) } } #[proc_macro_derive(Dialogue, attributes(dialogue))] #[proc_macro_error] pub fn derive_dialogue(input: TokenStream) -> TokenStream { let DeriveInput { ident, data, .. } = parse_macro_input!(input as DeriveInput); match data { Data::Enum(DataEnum { variants, .. }) => derive_on_enum(variants.iter(), ident), Data::Struct(DataStruct { fields: Fields::Named(ref fields), .. }) => derive_on_struct(fields, ident), _ => { abort_call_site!("Dialogue must be either Enum or Struct") } } .into() } fn derive_on_enum<'a>(variants: impl Iterator<Item = &'a Variant>, ident: Ident) -> TokenStream2 { let variants = variants.map(|v| { ( &v.ident, extract_type(&v.fields), extract_extra_config(&v.attrs), ) }); let mut opts = Vec::new(); let mut names = Vec::new(); for (i, (field, typ, extra_config)) in variants.enumerate() { let ExtraConfig { prompt, name } = extra_config; if let Some(typ) = typ { if prompt.is_none() { abort_call_site!("Missing promp attribute on an enum variant"); } opts.push(quote! { #i => #ident::#field(<#typ as dialoguer_trait::Dialogue>::compose(#prompt)?), }); } else { opts.push(quote! { #i => #ident::#field, }) } if let Some(name) = name { names.push(quote! { #name }); } else { names.push(quote! { stringify!(#field) }); } } let opts: TokenStream2 = opts.into_iter().collect(); quote! { impl dialoguer_trait::Dialogue for #ident { fn compose(prompt: &str) -> std::io::Result<Self> { use dialoguer_trait::dialoguer::Select; use dialoguer_trait::dialoguer::theme::ColorfulTheme; let selections = [#(#names),*]; let idx = Select::with_theme(&ColorfulTheme::default()) .with_prompt(prompt) .default(0) .items(&selections[..]) .interact()?; Ok(match idx { #opts _ => unreachable!(), }) } } } } fn extract_extra_config(attributes: &[Attribute]) -> ExtraConfig { let defs: DialogueDefsParenthesized = match attributes .iter() .find(|attr| attr.path == parse_quote!(dialogue)) { Some(attr) => syn::parse(attr.tokens.clone().into()).expect("Expected Def"), None => DialogueDefsParenthesized::default(), }; ExtraConfig { prompt: defs.inner.map.get("prompt").cloned(), name: defs.inner.map.get("name").cloned(), } } fn extract_type(fields: &Fields) -> Option<&Type> { match fields { Fields::Unnamed(FieldsUnnamed { ref unnamed, .. }) => match unnamed.len() { 1 => { let field = unnamed.first().unwrap(); Some(&field.ty) } _ => abort_call_site!("Only enum variants with single field are supported at a time"), }, Fields::Unit => None, _ => abort_call_site!("Only unnamed fields are supported for enums at the time"), } } fn derive_on_struct(fields: &FieldsNamed, ident: Ident) -> TokenStream2 { let mut acc = Vec::new(); for field in &fields.named { let ExtraConfig { prompt, .. } = extract_extra_config(&field.attrs); let ident = if let Some(ident) = field.ident.as_ref() { ident } else { abort_call_site!("Missing ident of struct field") }; let typ = &field.ty; acc.push(quote! { #ident: <#typ as dialoguer_trait::Dialogue>::compose(#prompt)?, }) } let fields: TokenStream2 = acc.into_iter().collect(); quote! { impl dialoguer_trait::Dialogue for #ident { fn compose(prompt: &str) -> std::io::Result<Self> { println!("{}", prompt); let result = #ident { #fields }; Ok(result) } } } }