1use proc_macro2::TokenStream;
2use quote::{quote, ToTokens};
3use syn::{Attribute, LitStr, Meta, Result};
4
5#[derive(Clone)]
6pub(crate) struct Display {
7 pub(crate) fmt: LitStr,
8 pub(crate) args: TokenStream,
9}
10
11pub(crate) struct VariantDisplay {
12 pub(crate) r#enum: Option<Display>,
13 pub(crate) variant: Display,
14}
15
16impl ToTokens for Display {
17 fn to_tokens(&self, tokens: &mut TokenStream) {
18 let fmt: &LitStr = &self.fmt;
19 let args: &TokenStream = &self.args;
20 tokens.extend(iter:quote! {
21 write!(formatter, #fmt #args)
22 });
23 }
24}
25
26impl ToTokens for VariantDisplay {
27 fn to_tokens(&self, tokens: &mut TokenStream) {
28 if let Some(ref r#enum: &Display) = self.r#enum {
29 r#enum.to_tokens(tokens);
30 tokens.extend(iter:quote! { ?; write!(formatter, ": ")?; });
31 }
32 self.variant.to_tokens(tokens);
33 }
34}
35
36pub(crate) struct AttrsHelper {
37 ignore_extra_doc_attributes: bool,
38 prefix_enum_doc_attributes: bool,
39}
40
41impl AttrsHelper {
42 pub(crate) fn new(attrs: &[Attribute]) -> Self {
43 let ignore_extra_doc_attributes = attrs
44 .iter()
45 .any(|attr| attr.path().is_ident("ignore_extra_doc_attributes"));
46 let prefix_enum_doc_attributes = attrs
47 .iter()
48 .any(|attr| attr.path().is_ident("prefix_enum_doc_attributes"));
49
50 Self {
51 ignore_extra_doc_attributes,
52 prefix_enum_doc_attributes,
53 }
54 }
55
56 pub(crate) fn display(&self, attrs: &[Attribute]) -> Result<Option<Display>> {
57 let displaydoc_attr = attrs.iter().find(|attr| attr.path().is_ident("displaydoc"));
58
59 if let Some(displaydoc_attr) = displaydoc_attr {
60 let lit = displaydoc_attr
61 .parse_args()
62 .expect("#[displaydoc(\"foo\")] must contain string arguments");
63 let mut display = Display {
64 fmt: lit,
65 args: TokenStream::new(),
66 };
67
68 display.expand_shorthand();
69 return Ok(Some(display));
70 }
71
72 let num_doc_attrs = attrs
73 .iter()
74 .filter(|attr| attr.path().is_ident("doc"))
75 .count();
76
77 if !self.ignore_extra_doc_attributes && num_doc_attrs > 1 {
78 panic!("Multi-line comments are disabled by default by displaydoc. Please consider using block doc comments (/** */) or adding the #[ignore_extra_doc_attributes] attribute to your type next to the derive.");
79 }
80
81 for attr in attrs {
82 if attr.path().is_ident("doc") {
83 let lit = match &attr.meta {
84 Meta::NameValue(syn::MetaNameValue {
85 value:
86 syn::Expr::Lit(syn::ExprLit {
87 lit: syn::Lit::Str(lit),
88 ..
89 }),
90 ..
91 }) => lit,
92 _ => unimplemented!(),
93 };
94
95 // Make an attempt at cleaning up multiline doc comments.
96 let doc_str = lit
97 .value()
98 .lines()
99 .map(|line| line.trim().trim_start_matches('*').trim())
100 .collect::<Vec<&str>>()
101 .join("\n");
102
103 let lit = LitStr::new(doc_str.trim(), lit.span());
104
105 let mut display = Display {
106 fmt: lit,
107 args: TokenStream::new(),
108 };
109
110 display.expand_shorthand();
111 return Ok(Some(display));
112 }
113 }
114
115 Ok(None)
116 }
117
118 pub(crate) fn display_with_input(
119 &self,
120 r#enum: &[Attribute],
121 variant: &[Attribute],
122 ) -> Result<Option<VariantDisplay>> {
123 let r#enum = if self.prefix_enum_doc_attributes {
124 let result = self
125 .display(r#enum)?
126 .expect("Missing doc comment on enum with #[prefix_enum_doc_attributes]. Please remove the attribute or add a doc comment to the enum itself.");
127
128 Some(result)
129 } else {
130 None
131 };
132
133 Ok(self
134 .display(variant)?
135 .map(|variant| VariantDisplay { r#enum, variant }))
136 }
137}
138

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