packable-derive 0.10.0

Derive macro for the `packable` crate.
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

// Copyright 2023 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

use syn::{
    parse::{Parse, ParseStream},
    Attribute, Error, Result,
};

use crate::parse::{parse_kv, skip_stream};

pub(crate) struct UnpackVisitorInfo {
    pub(crate) unpack_visitor: syn::Type,
    pub(crate) explicit: bool,
}

struct Type(syn::Type);

impl Parse for Type {
    fn parse(input: ParseStream) -> Result<Self> {
        syn::Type::parse(input).map(Self).map_err(|err| {
            Error::new(
                err.span(),
                "The `unpack_visitor` attribute requires a type for its value.",
            )
        })
    }
}

impl UnpackVisitorInfo {
    pub(crate) fn new<'a>(
        filtered_attrs: impl Iterator<Item = &'a Attribute>,
        default_unpack_visitor: impl FnOnce() -> Result<UnpackVisitorInfo>,
    ) -> Result<Self> {
        for attr in filtered_attrs {
            let opt_info =
                attr.parse_args_with(
                    |stream: ParseStream| match parse_kv::<Type>("unpack_visitor", stream)? {
                        Some(Type(unpack_visitor)) => Ok(Some(Self {
                            unpack_visitor,
                            explicit: true,
                        })),
                        None => {
                            skip_stream(stream)?;
                            Ok(None)
                        }
                    },
                )?;

            if let Some(info) = opt_info {
                return Ok(info);
            }
        }

        default_unpack_visitor()
    }
}