colorthis 0.1.1

Meta macros that aid macro authors to create colors from a generalized syntax.
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
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use proc_macro2::{TokenStream, TokenTree, Span, Spacing, Delimiter};
use proc_macro_error::abort;
use quote::quote;

enum PathSep {
    DoubleColon,
    Dot,
    Break,
}

impl PathSep {
    pub fn write_to(&self, tokens: &mut TokenStream) {
        match &self {
            PathSep::DoubleColon => tokens.extend(quote!(::)),
            PathSep::Dot => tokens.extend(quote!(.)),
            PathSep::Break => (),
        }
    }
}

fn extract_sep(iter: &mut proc_macro2::token_stream::IntoIter) -> PathSep{
    match iter.next() {
        Some(TokenTree::Punct(punct)) if punct.as_char() == ':' && punct.spacing() == Spacing::Joint => {
            match iter.next() {
                Some(TokenTree::Punct(punct)) if punct.as_char() == ':' => PathSep::DoubleColon,
                Some(tt) => abort!(tt.span(), "Expected '::'."),
                None => abort!(punct.span(), "Expected '::'."),
            }
        }
        Some(TokenTree::Punct(punct)) if punct.as_char() == '.' => {
            PathSep::Dot
        },
        Some(TokenTree::Punct(punct)) if punct.as_char() == ',' => {
            PathSep::Break
        },
        Some(tt) => abort!(tt.span(), "Expected one of ',', '.' or '::'."),
        None => abort!(Span::call_site(), "Expected one of ',', '.' or '::'."),
    }
}

/// Separate caller paths like `Rgba::new`, `::colors::rgba::rgba`, `color.set`, etc.
pub fn extract_path(tokens: TokenStream) -> (TokenStream, TokenTree, Option<TokenStream>) {
    let mut tokens = tokens.into_iter();
    let mut path = Vec::new();
    let path = loop {
        match tokens.next() {
            Some(TokenTree::Punct(p)) if p.as_char() == ',' => {
                break path.into_iter().collect();
            }
            Some(other) => {
                path.push(other)
            }
            None => {
                abort!(Span::call_site(), "Expected path.")
            }
        }
    };
    let color = match tokens.next(){
        Some(x) => x,
        None => abort!(Span::call_site(), "Expected color token tree."),
    };
    match (tokens.next(), tokens.next()) {
        (None, _) => return (path, color, None),
        (Some(TokenTree::Punct(a)), Some(TokenTree::Punct(b))) => {
            if a.as_char() != '=' || b.as_char() != '>' || a.spacing() != Spacing::Joint{
                abort!(a.span(), "Expected => , or end.")
            }
        }
        (Some(TokenTree::Punct(p)), None) => {
            if p.as_char() == ',' {
                return (path, color, None)
            } else {
                abort!(p.span(), "Expected => , or end.")
            }
        }
        (Some(tt), _) => abort!(tt.span(), "Expected => , or end.")
    }

    let fields = match tokens.next() {
        Some(TokenTree::Group(g)) if g.delimiter() == Delimiter::Brace => {
            g.stream()
        },
        Some(tt) => abort!(tt.span(), "Expected {fields}."),
        None => abort!(Span::call_site(), "Expected {fields}."),
    };

    match tokens.next() {
        Some(TokenTree::Punct(p)) if p.as_char() == ',' => {
            match tokens.next() {
                Some(t) => abort!(t.span(), "Expected end of arguments."),
                None => (),
            }
        },
        Some(tt) => abort!(tt.span(), "Expected end of arguments."),
        None => (),
    };

    (path, color, Some(fields))
}

#[cfg(test)]
mod test {
    use super::extract_path;
    use quote::quote;
    use std::mem::discriminant;

    #[macro_export]
    macro_rules! tokenstream_eq {
        ($left: expr, $right: expr ) => {
            for (a, b) in $left.into_iter().zip($right.into_iter()){
                assert_eq!(discriminant(&a), discriminant(&b));
                assert_eq!(a.to_string(), b.to_string())
            }
        };
    }

    #[test]
    pub fn test_path_extractor() {
        let (left, right, _) = extract_path(quote!(Color, [1234, 567]));
        tokenstream_eq!(left, quote!(Color));
        assert!(matches!(right, proc_macro2::TokenTree::Group(_)));
        
        let (left, right, _) = extract_path(quote!(rgba::Color, 0xFFFFFF));
        tokenstream_eq!(left, quote!(rgba::Color));
        assert!(matches!(right, proc_macro2::TokenTree::Literal(_)));

        let (left, right, _) = extract_path(quote!(::some::path::func, Red));
        tokenstream_eq!(left, quote!(::some::path::func));
        assert!(matches!(right, proc_macro2::TokenTree::Ident(_)));
    }
}