clap_derive/derives/
parser.rs

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1// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>,
2// Kevin Knapp (@kbknapp) <kbknapp@gmail.com>, and
3// Ana Hobden (@hoverbear) <operator@hoverbear.org>
4//
5// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8// option. This file may not be copied, modified, or distributed
9// except according to those terms.
10//
11// This work was derived from Structopt (https://github.com/TeXitoi/structopt)
12// commit#ea76fa1b1b273e65e3b0b1046643715b49bec51f which is licensed under the
13// MIT/Apache 2.0 license.
14
15use proc_macro2::TokenStream;
16use quote::quote;
17use syn::Ident;
18use syn::Variant;
19use syn::{
20    self, punctuated::Punctuated, token::Comma, Data, DataStruct, DeriveInput, Field, Fields,
21    Generics,
22};
23
24use crate::derives::args::collect_args_fields;
25use crate::derives::{args, into_app, subcommand};
26use crate::item::Item;
27use crate::item::Name;
28
29pub(crate) fn derive_parser(input: &DeriveInput) -> Result<TokenStream, syn::Error> {
30    let ident = &input.ident;
31    let pkg_name = std::env::var("CARGO_PKG_NAME").ok().unwrap_or_default();
32
33    match input.data {
34        Data::Struct(DataStruct {
35            fields: Fields::Named(ref fields),
36            ..
37        }) => {
38            let name = Name::Assigned(quote!(#pkg_name));
39            let item = Item::from_args_struct(input, name)?;
40            let fields = collect_args_fields(&item, fields)?;
41            gen_for_struct(&item, ident, &input.generics, &fields)
42        }
43        Data::Struct(DataStruct {
44            fields: Fields::Unit,
45            ..
46        }) => {
47            let name = Name::Assigned(quote!(#pkg_name));
48            let item = Item::from_args_struct(input, name)?;
49            let fields = Punctuated::<Field, Comma>::new();
50            let fields = fields
51                .iter()
52                .map(|field| {
53                    let item = Item::from_args_field(field, item.casing(), item.env_casing())?;
54                    Ok((field, item))
55                })
56                .collect::<Result<Vec<_>, syn::Error>>()?;
57            gen_for_struct(&item, ident, &input.generics, &fields)
58        }
59        Data::Enum(ref e) => {
60            let name = Name::Assigned(quote!(#pkg_name));
61            let item = Item::from_subcommand_enum(input, name)?;
62            let variants = e
63                .variants
64                .iter()
65                .map(|variant| {
66                    let item =
67                        Item::from_subcommand_variant(variant, item.casing(), item.env_casing())?;
68                    Ok((variant, item))
69                })
70                .collect::<Result<Vec<_>, syn::Error>>()?;
71            gen_for_enum(&item, ident, &input.generics, &variants)
72        }
73        _ => abort_call_site!("`#[derive(Parser)]` only supports non-tuple structs and enums"),
74    }
75}
76
77fn gen_for_struct(
78    item: &Item,
79    item_name: &Ident,
80    generics: &Generics,
81    fields: &[(&Field, Item)],
82) -> Result<TokenStream, syn::Error> {
83    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
84
85    let into_app = into_app::gen_for_struct(item, item_name, generics)?;
86    let args = args::gen_for_struct(item, item_name, generics, fields)?;
87
88    Ok(quote! {
89        #[automatically_derived]
90        #[allow(
91            unused_qualifications,
92            clippy::redundant_locals,
93        )]
94        impl #impl_generics clap::Parser for #item_name #ty_generics #where_clause {}
95
96        #into_app
97        #args
98    })
99}
100
101fn gen_for_enum(
102    item: &Item,
103    item_name: &Ident,
104    generics: &Generics,
105    variants: &[(&Variant, Item)],
106) -> Result<TokenStream, syn::Error> {
107    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
108
109    let into_app = into_app::gen_for_enum(item, item_name, generics)?;
110    let subcommand = subcommand::gen_for_enum(item, item_name, generics, variants)?;
111
112    Ok(quote! {
113        #[automatically_derived]
114        impl #impl_generics clap::Parser for #item_name #ty_generics #where_clause {}
115
116        #into_app
117        #subcommand
118    })
119}
clap_derive/derives/parser.rs

clap_derive/derives/
parser.rs
