clap_derive/utils/
ty.rs

1//! Special types handling
2
3use super::spanned::Sp;
4
5use syn::{
6    spanned::Spanned, GenericArgument, Path, PathArguments, PathArguments::AngleBracketed,
7    PathSegment, Type, TypePath,
8};
9
10#[derive(Copy, Clone, PartialEq, Eq, Debug)]
11pub(crate) enum Ty {
12    Unit,
13    Vec,
14    VecVec,
15    Option,
16    OptionOption,
17    OptionVec,
18    OptionVecVec,
19    Other,
20}
21
22impl Ty {
23    pub(crate) fn from_syn_ty(ty: &Type) -> Sp<Self> {
24        use self::Ty::{Option, OptionOption, OptionVec, OptionVecVec, Other, Unit, Vec, VecVec};
25        let t = |kind| Sp::new(kind, ty.span());
26
27        if is_unit_ty(ty) {
28            t(Unit)
29        } else if let Some(vt) = get_vec_ty(ty, Vec, VecVec) {
30            t(vt)
31        } else if let Some(subty) = subty_if_name(ty, "Option") {
32            if is_generic_ty(subty, "Option") {
33                t(OptionOption)
34            } else if let Some(vt) = get_vec_ty(subty, OptionVec, OptionVecVec) {
35                t(vt)
36            } else {
37                t(Option)
38            }
39        } else {
40            t(Other)
41        }
42    }
43
44    pub(crate) fn as_str(&self) -> &'static str {
45        match self {
46            Self::Unit => "()",
47            Self::Vec => "Vec<T>",
48            Self::Option => "Option<T>",
49            Self::OptionOption => "Option<Option<T>>",
50            Self::OptionVec => "Option<Vec<T>>",
51            Self::VecVec => "Vec<Vec<T>>",
52            Self::OptionVecVec => "Option<Vec<Vec<T>>>",
53            Self::Other => "...other...",
54        }
55    }
56}
57
58pub(crate) fn inner_type(field_ty: &Type) -> &Type {
59    let ty = Ty::from_syn_ty(field_ty);
60    match *ty {
61        Ty::Vec | Ty::Option => sub_type(field_ty).unwrap_or(field_ty),
62        Ty::OptionOption | Ty::OptionVec | Ty::VecVec => {
63            sub_type(field_ty).and_then(sub_type).unwrap_or(field_ty)
64        }
65        Ty::OptionVecVec => sub_type(field_ty)
66            .and_then(sub_type)
67            .and_then(sub_type)
68            .unwrap_or(field_ty),
69        _ => field_ty,
70    }
71}
72
73pub(crate) fn sub_type(ty: &Type) -> Option<&Type> {
74    subty_if(ty, |_| true)
75}
76
77fn only_last_segment(mut ty: &Type) -> Option<&PathSegment> {
78    while let Type::Group(syn::TypeGroup { elem, .. }) = ty {
79        ty = elem;
80    }
81    match ty {
82        Type::Path(TypePath {
83            qself: None,
84            path:
85                Path {
86                    leading_colon: None,
87                    segments,
88                },
89        }) => only_one(segments.iter()),
90
91        _ => None,
92    }
93}
94
95fn subty_if<F>(ty: &Type, f: F) -> Option<&Type>
96where
97    F: FnOnce(&PathSegment) -> bool,
98{
99    only_last_segment(ty)
100        .filter(|segment| f(segment))
101        .and_then(|segment| {
102            if let AngleBracketed(args) = &segment.arguments {
103                only_one(args.args.iter()).and_then(|genneric| {
104                    if let GenericArgument::Type(ty) = genneric {
105                        Some(ty)
106                    } else {
107                        None
108                    }
109                })
110            } else {
111                None
112            }
113        })
114}
115
116pub(crate) fn subty_if_name<'a>(ty: &'a Type, name: &str) -> Option<&'a Type> {
117    subty_if(ty, |seg| seg.ident == name)
118}
119
120pub(crate) fn is_simple_ty(ty: &Type, name: &str) -> bool {
121    only_last_segment(ty)
122        .map(|segment| {
123            if let PathArguments::None = segment.arguments {
124                segment.ident == name
125            } else {
126                false
127            }
128        })
129        .unwrap_or(false)
130}
131
132fn is_generic_ty(ty: &Type, name: &str) -> bool {
133    subty_if_name(ty, name).is_some()
134}
135
136fn is_unit_ty(ty: &Type) -> bool {
137    if let Type::Tuple(tuple) = ty {
138        tuple.elems.is_empty()
139    } else {
140        false
141    }
142}
143
144fn only_one<I, T>(mut iter: I) -> Option<T>
145where
146    I: Iterator<Item = T>,
147{
148    iter.next().filter(|_| iter.next().is_none())
149}
150
151#[cfg(feature = "unstable-v5")]
152fn get_vec_ty(ty: &Type, vec_ty: Ty, vecvec_ty: Ty) -> Option<Ty> {
153    subty_if_name(ty, "Vec").map(|subty| {
154        if is_generic_ty(subty, "Vec") {
155            vecvec_ty
156        } else {
157            vec_ty
158        }
159    })
160}
161
162#[cfg(not(feature = "unstable-v5"))]
163fn get_vec_ty(ty: &Type, vec_ty: Ty, _vecvec_ty: Ty) -> Option<Ty> {
164    is_generic_ty(ty, "Vec").then_some(vec_ty)
165}
clap_derive/utils/ty.rs

clap_derive/utils/
ty.rs
