gremlin-derive 0.1.0

Proc macro for gremlin-rs™
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96

use quote::quote;
use syn::{parse_quote, Data, DataStruct, DeriveInput, Fields, FieldsNamed, Stmt};

pub fn derive(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    match &input.data {
        Data::Struct(DataStruct {
            fields: Fields::Named(FieldsNamed { named, .. }),
            ..
        }) => {
            let ident = &input.ident;

            let (m_reads, m_names) = map_properties(named);

            Ok(quote! {

                impl std::convert::TryFrom<gremlin_client::GValue> for #ident {
                    type Error = gremlin_client::GremlinError;
                    fn try_from(result : gremlin_client::GValue) -> gremlin_client::GremlinResult<Self>{


                        match result {
                            gremlin_client::GValue::Map(map) => {
                                #(#m_reads)*

                                Ok(#ident {
                                    #(#m_names),*
                                })
                            }
                             _ => {
                                Err(gremlin_client::GremlinError::Cast(String::from("Cannot")))
                            }
                        }


                    }
                }
            })
        }
        _ => Err(syn::Error::new_spanned(
            input,
            "Only structs are supported for Repo derive",
        )),
    }
}

pub fn derive_map(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    match &input.data {
        Data::Struct(DataStruct {
            fields: Fields::Named(FieldsNamed { named, .. }),
            ..
        }) => {
            let ident = &input.ident;

            let (m_reads, m_names) = map_properties(named);

            Ok(quote! {

                impl std::convert::TryFrom<gremlin_client::Map> for #ident {
                    type Error = gremlin_client::GremlinError;
                    fn try_from(map : gremlin_client::Map) -> gremlin_client::GremlinResult<Self>{
                        #(#m_reads)*

                        Ok(#ident {
                            #(#m_names),*
                        })
                    }
                }
            })
        }
        _ => Err(syn::Error::new_spanned(
            input,
            "Only structs are supported for Repo derive",
        )),
    }
}

fn map_properties(
    named: &syn::punctuated::Punctuated<syn::Field, syn::token::Comma>,
) -> (Vec<Stmt>, Vec<&Option<proc_macro2::Ident>>) {
    let reads = named
        .iter()
        .filter_map(|field| -> Option<Stmt> {
            let id = &field.ident.as_ref()?;
            let id_s = id.to_string();
            let ty = &field.ty;

            Some(parse_quote!(
                let #id: #ty = map.try_get(#id_s)?;
            ))
        })
        .collect();

    let names = named.iter().map(|field| &field.ident).collect();

    (reads, names)
}