clap_derive/derives/
value_enum.rs

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
11use proc_macro2::TokenStream;
12use quote::quote;
13use quote::quote_spanned;
14use syn::{spanned::Spanned, Data, DeriveInput, Fields, Ident, Variant};
15
16use crate::item::{Item, Kind, Name};
17
18pub(crate) fn derive_value_enum(input: &DeriveInput) -> Result<TokenStream, syn::Error> {
19    let ident = &input.ident;
20
21    match input.data {
22        Data::Enum(ref e) => {
23            let name = Name::Derived(ident.clone());
24            let item = Item::from_value_enum(input, name)?;
25            let mut variants = Vec::new();
26            for variant in &e.variants {
27                let item =
28                    Item::from_value_enum_variant(variant, item.casing(), item.env_casing())?;
29                variants.push((variant, item));
30            }
31            gen_for_enum(&item, ident, &variants)
32        }
33        _ => abort_call_site!("`#[derive(ValueEnum)]` only supports enums"),
34    }
35}
36
37pub(crate) fn gen_for_enum(
38    item: &Item,
39    item_name: &Ident,
40    variants: &[(&Variant, Item)],
41) -> Result<TokenStream, syn::Error> {
42    if !matches!(&*item.kind(), Kind::Value) {
43        abort! { item.kind().span(),
44            "`{}` cannot be used with `value`",
45            item.kind().name(),
46        }
47    }
48
49    let lits = lits(variants)?;
50    let value_variants = gen_value_variants(&lits);
51    let to_possible_value = gen_to_possible_value(item, &lits);
52
53    Ok(quote! {
54        #[allow(
55            dead_code,
56            unreachable_code,
57            unused_variables,
58            unused_braces,
59            unused_qualifications,
60        )]
61        #[allow(
62            clippy::style,
63            clippy::complexity,
64            clippy::pedantic,
65            clippy::restriction,
66            clippy::perf,
67            clippy::deprecated,
68            clippy::nursery,
69            clippy::cargo,
70            clippy::suspicious_else_formatting,
71            clippy::almost_swapped,
72            clippy::redundant_locals,
73        )]
74        #[automatically_derived]
75        impl clap::ValueEnum for #item_name {
76            #value_variants
77            #to_possible_value
78        }
79    })
80}
81
82fn lits(variants: &[(&Variant, Item)]) -> Result<Vec<(TokenStream, Ident)>, syn::Error> {
83    let mut genned = Vec::new();
84    for (variant, item) in variants {
85        if let Kind::Skip(_, _) = &*item.kind() {
86            continue;
87        }
88        if !matches!(variant.fields, Fields::Unit) {
89            abort!(variant.span(), "`#[derive(ValueEnum)]` only supports unit variants. Non-unit variants must be skipped");
90        }
91        let fields = item.field_methods();
92        let deprecations = item.deprecations();
93        let name = item.cased_name();
94        genned.push((
95            quote_spanned! { variant.span()=> {
96                #deprecations
97                clap::builder::PossibleValue::new(#name)
98                #fields
99            }},
100            variant.ident.clone(),
101        ));
102    }
103    Ok(genned)
104}
105
106fn gen_value_variants(lits: &[(TokenStream, Ident)]) -> TokenStream {
107    let lit = lits.iter().map(|l| &l.1).collect::<Vec<_>>();
108
109    quote! {
110        fn value_variants<'a>() -> &'a [Self]{
111            &[#(Self::#lit),*]
112        }
113    }
114}
115
116fn gen_to_possible_value(item: &Item, lits: &[(TokenStream, Ident)]) -> TokenStream {
117    let (lit, variant): (Vec<TokenStream>, Vec<Ident>) = lits.iter().cloned().unzip();
118
119    let deprecations = item.deprecations();
120
121    quote! {
122        fn to_possible_value<'a>(&self) -> ::std::option::Option<clap::builder::PossibleValue> {
123            #deprecations
124            match self {
125                #(Self::#variant => Some(#lit),)*
126                _ => None
127            }
128        }
129    }
130}
clap_derive/derives/value_enum.rs

clap_derive/derives/
value_enum.rs
