diesel_enum_sqltype/
lib.rs

1extern crate proc_macro;
2
3use proc_macro::TokenStream;
4
5use proc_macro2::{Ident, Span};
6use quote::quote;
7use syn::punctuated::Punctuated;
8use syn::token::{Comma, Eq};
9use syn::{parse_macro_input, Attribute, Data, DeriveInput, Fields, LitByteStr, Variant};
10
11#[proc_macro_derive(FromSqlDerive, attributes(diesel))]
12pub fn from_sql_derive(input: TokenStream) -> TokenStream {
13    let DeriveInput {
14        ident, attrs, data, ..
15    } = parse_macro_input!(input as DeriveInput);
16
17    let (sql_type, variants) = parse_sql_type(attrs, data, "FromSqlDerive");
18
19    let from_sql_arms = variants.iter().map(|Variant { ident, fields, .. }| {
20        if let Fields::Unit = fields {
21            let ident_str = format!("{}", ident);
22            let ident_bytes = ident_str.as_bytes();
23            let ident_bytes = LitByteStr::new(ident_bytes, Span::call_site());
24            quote! { #ident_bytes => Ok(Self::#ident), }
25        } else {
26            panic!("FromSqlDerive can only be derived for enums with unit variants");
27        }
28    });
29
30    let gen = quote! {
31        impl diesel::deserialize::FromSql<#sql_type, diesel::pg::Pg> for #ident {
32            fn from_sql(bytes: diesel::pg::PgValue<'_>) -> diesel::deserialize::Result<Self> {
33                match bytes.as_bytes() {
34                    #(#from_sql_arms)*
35                    _ => Err("Unrecognized enum variant".into()),
36                }
37            }
38        }
39    };
40
41    gen.into()
42}
43
44#[proc_macro_derive(ToSqlDerive, attributes(diesel))]
45pub fn to_sql_derive(input: TokenStream) -> TokenStream {
46    let DeriveInput {
47        ident, attrs, data, ..
48    } = parse_macro_input!(input as DeriveInput);
49
50    let (sql_type, variants) = parse_sql_type(attrs, data, "ToSqlDerive");
51
52    let to_sql_arms = variants.iter().map(|Variant { ident, .. }| {
53        let ident_str = format!("{}", ident);
54        let ident_bytes = ident_str.as_bytes();
55        let ident_bytes = syn::LitByteStr::new(ident_bytes, proc_macro2::Span::call_site());
56
57        quote! { Self::#ident => { out.write_all(#ident_bytes)?; } }
58    });
59
60    let gen = quote! {
61                impl diesel::serialize::ToSql<#sql_type, diesel::pg::Pg> for #ident {
62            fn to_sql<'b>(&'b self, out: &mut diesel::serialize::Output<'b,'_, diesel::pg::Pg>) -> diesel::serialize::Result {
63                match *self {
64                    #(#to_sql_arms)*
65                }
66                Ok(diesel::serialize::IsNull::No)
67            }
68        }
69    };
70
71    gen.into()
72}
73
74fn parse_sql_type(
75    attrs: Vec<Attribute>,
76    data: Data,
77    kind: &str,
78) -> (Ident, Punctuated<Variant, Comma>) {
79    let sql_type: Vec<Ident> = attrs
80        .iter()
81        .filter(|a| a.path().is_ident("diesel"))
82        .flat_map(|a| {
83            let mut p = Vec::new();
84            let parser = a
85                .parse_args_with(Punctuated::<syn::Ident, Eq>::parse_separated_nonempty)
86                .unwrap();
87            let ident = parser.first().cloned().map(|f| f.to_string());
88            let value = parser.last().cloned();
89            if let Some("sql_type") = ident.as_deref() {
90                if let Some(value) = value {
91                    p.push(value)
92                }
93            }
94            p
95        })
96        .collect();
97
98    let sql_type = match sql_type.last() {
99        Some(idnt) => idnt,
100        None => panic!("Expected attribute diesel(sql_type=\"YourSqlType\")"),
101    };
102
103    let variants = if let Data::Enum(data) = data {
104        data.variants
105    } else {
106        panic!("{} can only be derived for enums", kind);
107    };
108
109    (sql_type.to_owned(), variants)
110}
diesel_enum_sqltype/lib.rs

diesel_enum_sqltype/
lib.rs
