1 | use crate::{util::SpannedValue, Error, Result}; |
2 | use std::fmt; |
3 | use syn::{punctuated::Pair, spanned::Spanned, token, Attribute, Meta, MetaList, Path}; |
4 | |
5 | /// Try to parse an attribute into a meta list. Path-type meta values are accepted and returned |
6 | /// as empty lists with their passed-in path. Name-value meta values and non-meta attributes |
7 | /// will cause errors to be returned. |
8 | pub fn parse_attribute_to_meta_list(attr: &Attribute) -> Result<MetaList> { |
9 | match attr.parse_meta() { |
10 | Ok(Meta::List(list: MetaList)) => Ok(list), |
11 | Ok(Meta::NameValue(nv: MetaNameValue)) => Err(Error::custom(format!( |
12 | "Name-value arguments are not supported. Use #[ {}(...)]" , |
13 | DisplayPath(&nv.path) |
14 | )) |
15 | .with_span(&nv)), |
16 | Ok(Meta::Path(path: Path)) => Ok(MetaList { |
17 | path, |
18 | paren_token: token::Paren(attr.span()), |
19 | nested: Default::default(), |
20 | }), |
21 | Err(e: Error) => Err(Error::custom(format!("Unable to parse attribute: {}" , e)) |
22 | .with_span(&SpannedValue::new((), e.span()))), |
23 | } |
24 | } |
25 | |
26 | struct DisplayPath<'a>(&'a Path); |
27 | |
28 | impl fmt::Display for DisplayPath<'_> { |
29 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
30 | let path: &Path = self.0; |
31 | if path.leading_colon.is_some() { |
32 | write!(f, "::" )?; |
33 | } |
34 | for segment: Pair<&PathSegment, &Colon2> in path.segments.pairs() { |
35 | match segment { |
36 | Pair::Punctuated(segment: &PathSegment, _) => write!(f, " {}::" , segment.ident)?, |
37 | Pair::End(segment: &PathSegment) => segment.ident.fmt(f)?, |
38 | } |
39 | } |
40 | |
41 | Ok(()) |
42 | } |
43 | } |
44 | |
45 | #[cfg (test)] |
46 | mod tests { |
47 | use super::parse_attribute_to_meta_list; |
48 | use syn::{parse_quote, spanned::Spanned, Ident}; |
49 | |
50 | #[test ] |
51 | fn parse_list() { |
52 | let meta = parse_attribute_to_meta_list(&parse_quote!(#[bar(baz = 4)])).unwrap(); |
53 | assert_eq!(meta.nested.len(), 1); |
54 | } |
55 | |
56 | #[test ] |
57 | fn parse_path_returns_empty_list() { |
58 | let meta = parse_attribute_to_meta_list(&parse_quote!(#[bar])).unwrap(); |
59 | assert!(meta.path.is_ident(&Ident::new("bar" , meta.path.span()))); |
60 | assert!(meta.nested.is_empty()); |
61 | } |
62 | |
63 | #[test ] |
64 | fn parse_name_value_returns_error() { |
65 | parse_attribute_to_meta_list(&parse_quote!(#[bar = 4])).unwrap_err(); |
66 | } |
67 | |
68 | #[test ] |
69 | fn parse_name_value_error_includes_example() { |
70 | let err = parse_attribute_to_meta_list(&parse_quote!(#[bar = 4])).unwrap_err(); |
71 | assert!(err.to_string().contains("#[bar(...)]" )); |
72 | } |
73 | } |
74 | |