envoke_derive 0.1.3

A proc macro for loading environment variables into struct fields automatically.
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
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112

//! # envoke_derive
//!
//! Derive macro for `envoke`. Learn more [here!](https://docs.rs/envoke)
//!
//! </br>
//!
//! #### License
//!
//! <sup>
//! Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
//! 2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
//! </sup>
//!
//! </br>
//!
//! <sub>
//! Unless you explicitly state otherwise, any contribution intentionally
//! submitted for inclusion in this crate by you, as defined in the Apache-2.0
//! license, shall be dual licensed as above, without any additional terms or
//! conditions. </sub>

use attr::{ContainerAttributes, FieldAttributes};
use proc_macro::TokenStream;
use proc_macro2::Ident;
use quote::quote;
use syn::{parse_macro_input, DeriveInput, Type};
use utils::{default_call, env_call, get_fields};

mod attr;
mod utils;

#[derive(Debug)]
struct Field {
    ident: Option<Ident>,
    ty: Type,
    attrs: FieldAttributes,
}

impl TryFrom<syn::Field> for Field {
    type Error = syn::Error;

    fn try_from(field: syn::Field) -> Result<Self, Self::Error> {
        let attrs = FieldAttributes::parse_attrs(&field, &field.attrs)?;

        Ok(Self {
            ident: field.ident,
            ty: field.ty,
            attrs,
        })
    }
}

#[doc(hidden)]
#[proc_macro_derive(Fill, attributes(fill))]
pub fn derive(input: TokenStream) -> TokenStream {
    let input: DeriveInput = parse_macro_input!(input);
    let struct_name = &input.ident;

    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

    let attrs = match ContainerAttributes::parse_attrs(&input.attrs) {
        Ok(attrs) => attrs,
        Err(e) => panic!("error: failed to parse container attributes for `{struct_name}`: {e}"),
    };

    let mut field_assignments = Vec::new();

    let fields = get_fields(input.data);
    for field in fields.named {
        let field = match Field::try_from(field) {
            Ok(field) => field,
            Err(e) => panic!("error: {e}"),
        };

        let ident = &field.ident;
        let ty = &field.ty;

        let value_call = if field.attrs.nested {
            quote! {
                <#ty as envoke::Envoke>::try_envoke()?
            }
        } else if field.attrs.envs.is_some() {
            env_call(&attrs, &field)
        } else if field.attrs.default.is_some() {
            default_call(&field)
        } else {
            quote! {
                panic!(format!("atleast one of field attributes `nested`, `env`, or `default` is required to be set for `{}`", #ident))
            }
        };

        let call = quote! {
            #ident: #value_call
        };

        field_assignments.push(call);
    }

    let expanded = quote! {
        impl #impl_generics envoke::Envoke for #struct_name #ty_generics #where_clause {
            fn try_envoke() -> envoke::Result<#struct_name #ty_generics> {
                use envoke::{Envloader, FromSingleOpt, FromMap, FromMapOpt, FromSet, FromSetOpt};

                Ok(#struct_name {
                    #(#field_assignments),*
                })
            }
        }
    };

    TokenStream::from(expanded)
}