diesel_derives/
queryable.rs

1use proc_macro2::{Span, TokenStream};
2use quote::quote;
3use syn::{parse_quote, DeriveInput, Ident, Index, Result};
4
5use crate::field::Field;
6use crate::model::Model;
7use crate::util::wrap_in_dummy_mod;
8
9pub fn derive(item: DeriveInput) -> Result<TokenStream> {
10    let model = Model::from_item(&item, false, true)?;
11
12    let struct_name = &item.ident;
13    let field_ty = &model
14        .fields()
15        .iter()
16        .map(Field::ty_for_deserialize)
17        .collect::<Vec<_>>();
18    let build_expr = model.fields().iter().enumerate().map(|(i, f)| {
19        let field_name = &f.name;
20        let i = Index::from(i);
21        // we explicitly call `.try_into()` here
22        // instead of using the fully qualified variant
23        // to allow also using a `.try_into()` method on the type
24        // itself without going through the trait
25        quote!(#field_name: row.#i.try_into()?)
26    });
27    let sql_type = &(0..model.fields().len())
28        .map(|i| {
29            let i = Ident::new(&format!("__ST{i}"), Span::mixed_site());
30            quote!(#i)
31        })
32        .collect::<Vec<_>>();
33
34    let (_, ty_generics, _) = item.generics.split_for_impl();
35    let mut generics = item.generics.clone();
36    generics
37        .params
38        .push(parse_quote!(__DB: diesel::backend::Backend));
39    for id in 0..model.fields().len() {
40        let ident = Ident::new(&format!("__ST{id}"), Span::mixed_site());
41        generics.params.push(parse_quote!(#ident));
42    }
43    {
44        let where_clause = generics.where_clause.get_or_insert(parse_quote!(where));
45        where_clause
46            .predicates
47            .push(parse_quote!((#(#field_ty,)*): diesel::deserialize::FromStaticSqlRow<(#(#sql_type,)*), __DB>));
48    }
49    let (impl_generics, _, where_clause) = generics.split_for_impl();
50
51    Ok(wrap_in_dummy_mod(quote! {
52        use diesel::row::{Row as _, Field as _};
53
54        impl #impl_generics diesel::deserialize::Queryable<(#(#sql_type,)*), __DB> for #struct_name #ty_generics
55            #where_clause
56        {
57            type Row = (#(#field_ty,)*);
58
59            fn build(row: (#(#field_ty,)*)) -> diesel::deserialize::Result<Self> {
60                use std::convert::TryInto;
61                Ok(Self {
62                    #(#build_expr,)*
63                })
64            }
65        }
66    }))
67}
diesel_derives/queryable.rs

diesel_derives/
queryable.rs
