zookeeper_derive/
lib.rs

1#![crate_type = "proc-macro"]
2
3extern crate syn;
4#[macro_use]
5extern crate quote;
6extern crate proc_macro;
7
8use proc_macro::TokenStream;
9use std::iter::Iterator;
10
11/// Emit an `std::fmt::Display` implementation for an enum type.
12#[proc_macro_derive(EnumDisplay)]
13pub fn emit_enum_display(input: TokenStream) -> TokenStream {
14    let ast: syn::DeriveInput = syn::parse(input).unwrap();
15
16    let name = &ast.ident;
17
18    let toks = quote! {
19        impl ::std::fmt::Display for #name {
20            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
21                write!(f, "{:?}", self)
22            }
23        }
24    };
25
26    toks.into()
27}
28
29/// Emit an `std::error::Error` implementation for an enum type. This is most useful in conjunction
30/// with `Debug` and `EnumDisplay`.
31#[proc_macro_derive(EnumError)]
32pub fn emit_enum_error(input: TokenStream) -> TokenStream {
33    let ast: syn::DeriveInput = syn::parse(input).unwrap();
34
35    let name = &ast.ident;
36
37    let en = match ast.data {
38        syn::Data::Enum(ref v) => v,
39        _ => panic!("EnumError only works for enum types"),
40    };
41
42    let mut serializations = Vec::new();
43
44    for variant in &en.variants {
45        let ident = &variant.ident;
46        let ident_str = format!("{}", ident);
47        serializations.push(quote! {
48            &#name::#ident => #ident_str
49        });
50    }
51
52    let toks = quote! {
53        impl ::std::error::Error for #name {
54            fn description(&self) -> &str {
55                match self {
56                    #(#serializations),*
57                }
58            }
59        }
60    };
61
62    toks.into()
63}
64
65/// Emit an `std::convert::From<i32>` implementation for an enum type. When converting from an `i32`
66/// that does not have an enumeration value, the system will panic, unless a fallback enumeration
67/// symbol is specified with `#[EnumConvertFromIntFallback = "Identifier"]`.
68#[proc_macro_derive(EnumConvertFromInt, attributes(EnumConvertFromIntFallback))]
69pub fn emit_enum_from_primitive(input: TokenStream) -> TokenStream {
70    let ast: syn::DeriveInput = syn::parse(input).unwrap();
71
72    let name = &ast.ident;
73
74    let en = match ast.data {
75        syn::Data::Enum(ref v) => v,
76        _ => panic!("EnumConvertFromInt only works for enum types"),
77    };
78
79    let mut serializations = Vec::new();
80
81    for variant in &en.variants {
82        let ident = &variant.ident;
83        let val = &match variant.discriminant {
84            Some(ref expr) => &expr.1,
85            None => panic!("{}::{} does not have an associated value", name, ident),
86        };
87        serializations.push(quote! {
88            #val => #name::#ident
89        });
90    }
91
92    let is_fallback_value = |attr: &syn::Attribute| match attr.parse_meta() {
93        Ok(syn::Meta::NameValue(syn::MetaNameValue { path, .. })) => {
94            path.is_ident("EnumConvertFromIntFallback")
95        }
96        _ => false,
97    };
98    let fallback = match ast.attrs.into_iter().find(&is_fallback_value) {
99        Some(attr) => match attr.parse_meta() {
100            Ok(syn::Meta::NameValue(syn::MetaNameValue {
101                lit: syn::Lit::Str(val),
102                ..
103            })) => {
104                let id = syn::Ident::new(&val.value(), val.span());
105                quote! { #name::#id }
106            }
107            _ => panic!("EnumConvertFromIntFallback must be a string"),
108        },
109        None => quote! { panic!("Received unexpected value {}", val) },
110    };
111
112    let toks = quote! {
113        impl ::std::convert::From<i32> for #name {
114            fn from(val: i32) -> #name {
115                match val {
116                    #(#serializations),*,
117                    _ => #fallback
118                }
119            }
120        }
121    };
122
123    toks.into()
124}
zookeeper_derive/lib.rs

zookeeper_derive/
lib.rs
