1 //! Utilities for manipulating C/C++ comments.
2
3 /// The type of a comment.
4 #[derive(Debug, PartialEq, Eq)]
5 enum Kind {
6 /// A `///` comment, or something of the like.
7 /// All lines in a comment should start with the same symbol.
8 SingleLines,
9 /// A `/**` comment, where each other line can start with `*` and the
10 /// entire block ends with `*/`.
11 MultiLine,
12 }
13
14 /// Preprocesses a C/C++ comment so that it is a valid Rust comment.
preprocess(comment: &str) -> String15 pub(crate) fn preprocess(comment: &str) -> String {
16 match self::kind(comment) {
17 Some(Kind::SingleLines) => preprocess_single_lines(comment),
18 Some(Kind::MultiLine) => preprocess_multi_line(comment),
19 None => comment.to_owned(),
20 }
21 }
22
23 /// Gets the kind of the doc comment, if it is one.
kind(comment: &str) -> Option<Kind>24 fn kind(comment: &str) -> Option<Kind> {
25 if comment.starts_with("/*") {
26 Some(Kind::MultiLine)
27 } else if comment.starts_with("//") {
28 Some(Kind::SingleLines)
29 } else {
30 None
31 }
32 }
33
34 /// Preprocesses multiple single line comments.
35 ///
36 /// Handles lines starting with both `//` and `///`.
preprocess_single_lines(comment: &str) -> String37 fn preprocess_single_lines(comment: &str) -> String {
38 debug_assert!(comment.starts_with("//"), "comment is not single line");
39
40 let lines: Vec<_> = comment
41 .lines()
42 .map(|l| l.trim().trim_start_matches('/'))
43 .collect();
44 lines.join("\n")
45 }
46
preprocess_multi_line(comment: &str) -> String47 fn preprocess_multi_line(comment: &str) -> String {
48 let comment = comment
49 .trim_start_matches('/')
50 .trim_end_matches('/')
51 .trim_end_matches('*');
52
53 // Strip any potential `*` characters preceding each line.
54 let mut lines: Vec<_> = comment
55 .lines()
56 .map(|line| line.trim().trim_start_matches('*').trim_start_matches('!'))
57 .skip_while(|line| line.trim().is_empty()) // Skip the first empty lines.
58 .collect();
59
60 // Remove the trailing line corresponding to the `*/`.
61 if lines.last().map_or(false, |l| l.trim().is_empty()) {
62 lines.pop();
63 }
64
65 lines.join("\n")
66 }
67
68 #[cfg(test)]
69 mod test {
70 use super::*;
71
72 #[test]
picks_up_single_and_multi_line_doc_comments()73 fn picks_up_single_and_multi_line_doc_comments() {
74 assert_eq!(kind("/// hello"), Some(Kind::SingleLines));
75 assert_eq!(kind("/** world */"), Some(Kind::MultiLine));
76 }
77
78 #[test]
processes_single_lines_correctly()79 fn processes_single_lines_correctly() {
80 assert_eq!(preprocess("///"), "");
81 assert_eq!(preprocess("/// hello"), " hello");
82 assert_eq!(preprocess("// hello"), " hello");
83 assert_eq!(preprocess("// hello"), " hello");
84 }
85
86 #[test]
processes_multi_lines_correctly()87 fn processes_multi_lines_correctly() {
88 assert_eq!(preprocess("/**/"), "");
89
90 assert_eq!(
91 preprocess("/** hello \n * world \n * foo \n */"),
92 " hello\n world\n foo"
93 );
94
95 assert_eq!(
96 preprocess("/**\nhello\n*world\n*foo\n*/"),
97 "hello\nworld\nfoo"
98 );
99 }
100 }
101