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, indent: usize) -> String15 pub fn preprocess(comment: &str, indent: usize) -> String {
16 match self::kind(comment) {
17 Some(Kind::SingleLines) => preprocess_single_lines(comment, indent),
18 Some(Kind::MultiLine) => preprocess_multi_line(comment, indent),
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
make_indent(indent: usize) -> String34 fn make_indent(indent: usize) -> String {
35 const RUST_INDENTATION: usize = 4;
36 " ".repeat(indent * RUST_INDENTATION)
37 }
38
39 /// Preprocesses multiple single line comments.
40 ///
41 /// Handles lines starting with both `//` and `///`.
preprocess_single_lines(comment: &str, indent: usize) -> String42 fn preprocess_single_lines(comment: &str, indent: usize) -> String {
43 debug_assert!(comment.starts_with("//"), "comment is not single line");
44
45 let indent = make_indent(indent);
46 let mut is_first = true;
47 let lines: Vec<_> = comment
48 .lines()
49 .map(|l| l.trim().trim_start_matches('/'))
50 .map(|l| {
51 let indent = if is_first { "" } else { &*indent };
52 is_first = false;
53 format!("{}///{}", indent, l)
54 })
55 .collect();
56 lines.join("\n")
57 }
58
preprocess_multi_line(comment: &str, indent: usize) -> String59 fn preprocess_multi_line(comment: &str, indent: usize) -> String {
60 let comment = comment
61 .trim_start_matches('/')
62 .trim_end_matches('/')
63 .trim_end_matches('*');
64
65 let indent = make_indent(indent);
66 // Strip any potential `*` characters preceding each line.
67 let mut is_first = true;
68 let mut lines: Vec<_> = comment
69 .lines()
70 .map(|line| line.trim().trim_start_matches('*').trim_start_matches('!'))
71 .skip_while(|line| line.trim().is_empty()) // Skip the first empty lines.
72 .map(|line| {
73 let indent = if is_first { "" } else { &*indent };
74 is_first = false;
75 format!("{}///{}", indent, line)
76 })
77 .collect();
78
79 // Remove the trailing line corresponding to the `*/`.
80 if lines
81 .last()
82 .map_or(false, |l| l.trim().is_empty() || l.trim() == "///")
83 {
84 lines.pop();
85 }
86
87 lines.join("\n")
88 }
89
90 #[cfg(test)]
91 mod test {
92 use super::*;
93
94 #[test]
picks_up_single_and_multi_line_doc_comments()95 fn picks_up_single_and_multi_line_doc_comments() {
96 assert_eq!(kind("/// hello"), Some(Kind::SingleLines));
97 assert_eq!(kind("/** world */"), Some(Kind::MultiLine));
98 }
99
100 #[test]
processes_single_lines_correctly()101 fn processes_single_lines_correctly() {
102 assert_eq!(preprocess("/// hello", 0), "/// hello");
103 assert_eq!(preprocess("// hello", 0), "/// hello");
104 assert_eq!(preprocess("// hello", 0), "/// hello");
105 }
106
107 #[test]
processes_multi_lines_correctly()108 fn processes_multi_lines_correctly() {
109 assert_eq!(
110 preprocess("/** hello \n * world \n * foo \n */", 0),
111 "/// hello\n/// world\n/// foo"
112 );
113
114 assert_eq!(
115 preprocess("/**\nhello\n*world\n*foo\n*/", 0),
116 "///hello\n///world\n///foo"
117 );
118 }
119 }
120