prost_derive/field/
message.rs

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1use anyhow::{bail, Error};
2use proc_macro2::TokenStream;
3use quote::{quote, ToTokens};
4use syn::Meta;
5
6use crate::field::{set_bool, set_option, tag_attr, word_attr, Label};
7
8#[derive(Clone)]
9pub struct Field {
10    pub label: Label,
11    pub tag: u32,
12}
13
14impl Field {
15    pub fn new(attrs: &[Meta], inferred_tag: Option<u32>) -> Result<Option<Field>, Error> {
16        let mut message = false;
17        let mut label = None;
18        let mut tag = None;
19        let mut boxed = false;
20
21        let mut unknown_attrs = Vec::new();
22
23        for attr in attrs {
24            if word_attr("message", attr) {
25                set_bool(&mut message, "duplicate message attribute")?;
26            } else if word_attr("boxed", attr) {
27                set_bool(&mut boxed, "duplicate boxed attribute")?;
28            } else if let Some(t) = tag_attr(attr)? {
29                set_option(&mut tag, t, "duplicate tag attributes")?;
30            } else if let Some(l) = Label::from_attr(attr) {
31                set_option(&mut label, l, "duplicate label attributes")?;
32            } else {
33                unknown_attrs.push(attr);
34            }
35        }
36
37        if !message {
38            return Ok(None);
39        }
40
41        if !unknown_attrs.is_empty() {
42            bail!(
43                "unknown attribute(s) for message field: #[prost({})]",
44                quote!(#(#unknown_attrs),*)
45            );
46        }
47
48        let tag = match tag.or(inferred_tag) {
49            Some(tag) => tag,
50            None => bail!("message field is missing a tag attribute"),
51        };
52
53        Ok(Some(Field {
54            label: label.unwrap_or(Label::Optional),
55            tag,
56        }))
57    }
58
59    pub fn new_oneof(attrs: &[Meta]) -> Result<Option<Field>, Error> {
60        if let Some(mut field) = Field::new(attrs, None)? {
61            if let Some(attr) = attrs.iter().find(|attr| Label::from_attr(attr).is_some()) {
62                bail!(
63                    "invalid attribute for oneof field: {}",
64                    attr.path().into_token_stream()
65                );
66            }
67            field.label = Label::Required;
68            Ok(Some(field))
69        } else {
70            Ok(None)
71        }
72    }
73
74    pub fn encode(&self, ident: TokenStream) -> TokenStream {
75        let tag = self.tag;
76        match self.label {
77            Label::Optional => quote! {
78                if let Some(ref msg) = #ident {
79                    ::prost::encoding::message::encode(#tag, msg, buf);
80                }
81            },
82            Label::Required => quote! {
83                ::prost::encoding::message::encode(#tag, &#ident, buf);
84            },
85            Label::Repeated => quote! {
86                for msg in &#ident {
87                    ::prost::encoding::message::encode(#tag, msg, buf);
88                }
89            },
90        }
91    }
92
93    pub fn merge(&self, ident: TokenStream) -> TokenStream {
94        match self.label {
95            Label::Optional => quote! {
96                ::prost::encoding::message::merge(wire_type,
97                                                 #ident.get_or_insert_with(::core::default::Default::default),
98                                                 buf,
99                                                 ctx)
100            },
101            Label::Required => quote! {
102                ::prost::encoding::message::merge(wire_type, #ident, buf, ctx)
103            },
104            Label::Repeated => quote! {
105                ::prost::encoding::message::merge_repeated(wire_type, #ident, buf, ctx)
106            },
107        }
108    }
109
110    pub fn encoded_len(&self, ident: TokenStream) -> TokenStream {
111        let tag = self.tag;
112        match self.label {
113            Label::Optional => quote! {
114                #ident.as_ref().map_or(0, |msg| ::prost::encoding::message::encoded_len(#tag, msg))
115            },
116            Label::Required => quote! {
117                ::prost::encoding::message::encoded_len(#tag, &#ident)
118            },
119            Label::Repeated => quote! {
120                ::prost::encoding::message::encoded_len_repeated(#tag, &#ident)
121            },
122        }
123    }
124
125    pub fn clear(&self, ident: TokenStream) -> TokenStream {
126        match self.label {
127            Label::Optional => quote!(#ident = ::core::option::Option::None),
128            Label::Required => quote!(#ident.clear()),
129            Label::Repeated => quote!(#ident.clear()),
130        }
131    }
132}
prost_derive/field/message.rs

prost_derive/field/
message.rs
