diesel_derives/
valid_grouping.rs

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1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::parse_quote;
4use syn::DeriveInput;
5use syn::Result;
6
7use crate::model::Model;
8use crate::util::{ty_for_foreign_derive, wrap_in_dummy_mod};
9
10pub fn derive(mut item: DeriveInput) -> Result<TokenStream> {
11    let model = Model::from_item(&item, true, false)?;
12    let struct_ty = ty_for_foreign_derive(&item, &model)?;
13
14    let type_params = item
15        .generics
16        .type_params()
17        .map(|param| param.ident.clone())
18        .collect::<Vec<_>>();
19
20    for type_param in type_params {
21        let where_clause = item.generics.make_where_clause();
22        where_clause
23            .predicates
24            .push(parse_quote!(#type_param: ValidGrouping<__GroupByClause>));
25    }
26
27    if model.aggregate {
28        item.generics.params.push(parse_quote!(__GroupByClause));
29        let (impl_generics, _, where_clause) = item.generics.split_for_impl();
30
31        Ok(wrap_in_dummy_mod(quote! {
32            use diesel::expression::{ValidGrouping, MixedAggregates, is_aggregate};
33
34            impl #impl_generics ValidGrouping<__GroupByClause> for #struct_ty
35            #where_clause
36            {
37                type IsAggregate = is_aggregate::Yes;
38            }
39        }))
40    } else {
41        let mut aggregates = item
42            .generics
43            .type_params()
44            .map(|t| quote!(#t::IsAggregate))
45            .collect::<Vec<_>>()
46            .into_iter();
47
48        let is_aggregate = aggregates
49            .next()
50            .map(|first| {
51                let where_clause = item.generics.make_where_clause();
52                aggregates.fold(first, |left, right| {
53                    where_clause.predicates.push(parse_quote!(
54                        #left: MixedAggregates<#right>
55                    ));
56                    quote!(<#left as MixedAggregates<#right>>::Output)
57                })
58            })
59            .unwrap_or_else(|| quote!(is_aggregate::Never));
60
61        item.generics.params.push(parse_quote!(__GroupByClause));
62        let (impl_generics, _, where_clause) = item.generics.split_for_impl();
63
64        Ok(wrap_in_dummy_mod(quote! {
65            use diesel::expression::{ValidGrouping, MixedAggregates, is_aggregate};
66
67            impl #impl_generics ValidGrouping<__GroupByClause> for #struct_ty
68            #where_clause
69            {
70                type IsAggregate = #is_aggregate;
71            }
72        }))
73    }
74}
diesel_derives/valid_grouping.rs

diesel_derives/
valid_grouping.rs
