wasmtime_wit_bindgen/
source.rs

1use std::fmt::{self, Write};
2use std::ops::Deref;
3
4/// Helper structure to maintain indentation automatically when printing.
5#[derive(Default)]
6pub struct Source {
7    s: String,
8    indent: usize,
9}
10
11impl Source {
12    pub fn push_str(&mut self, src: &str) {
13        let lines = src.lines().collect::<Vec<_>>();
14        for (i, line) in lines.iter().enumerate() {
15            let trimmed = line.trim();
16            if trimmed.starts_with('}') && self.s.ends_with("  ") {
17                self.s.pop();
18                self.s.pop();
19            }
20            self.s.push_str(if lines.len() == 1 {
21                line
22            } else {
23                line.trim_start()
24            });
25            if trimmed.ends_with('{') {
26                self.indent += 1;
27            }
28            if trimmed.starts_with('}') {
29                // Note that a `saturating_sub` is used here to prevent a panic
30                // here in the case of invalid code being generated in debug
31                // mode. It's typically easier to debug those issues through
32                // looking at the source code rather than getting a panic.
33                self.indent = self.indent.saturating_sub(1);
34            }
35            if i != lines.len() - 1 || src.ends_with('\n') {
36                self.newline();
37            }
38        }
39    }
40
41    pub fn indent(&mut self, amt: usize) {
42        self.indent += amt;
43    }
44
45    pub fn deindent(&mut self, amt: usize) {
46        self.indent -= amt;
47    }
48
49    fn newline(&mut self) {
50        self.s.push('\n');
51        for _ in 0..self.indent {
52            self.s.push_str("  ");
53        }
54    }
55
56    pub fn as_mut_string(&mut self) -> &mut String {
57        &mut self.s
58    }
59}
60
61impl Write for Source {
62    fn write_str(&mut self, s: &str) -> fmt::Result {
63        self.push_str(s);
64        Ok(())
65    }
66}
67
68impl Deref for Source {
69    type Target = str;
70    fn deref(&self) -> &str {
71        &self.s
72    }
73}
74
75impl From<Source> for String {
76    fn from(s: Source) -> String {
77        s.s
78    }
79}
80
81#[cfg(test)]
82mod tests {
83    use super::Source;
84
85    #[test]
86    fn simple_append() {
87        let mut s = Source::default();
88        s.push_str("x");
89        assert_eq!(s.s, "x");
90        s.push_str("y");
91        assert_eq!(s.s, "xy");
92        s.push_str("z ");
93        assert_eq!(s.s, "xyz ");
94        s.push_str(" a ");
95        assert_eq!(s.s, "xyz  a ");
96        s.push_str("\na");
97        assert_eq!(s.s, "xyz  a \na");
98    }
99
100    #[test]
101    fn newline_remap() {
102        let mut s = Source::default();
103        s.push_str("function() {\n");
104        s.push_str("y\n");
105        s.push_str("}\n");
106        assert_eq!(s.s, "function() {\n  y\n}\n");
107    }
108
109    #[test]
110    fn if_else() {
111        let mut s = Source::default();
112        s.push_str("if() {\n");
113        s.push_str("y\n");
114        s.push_str("} else if () {\n");
115        s.push_str("z\n");
116        s.push_str("}\n");
117        assert_eq!(s.s, "if() {\n  y\n} else if () {\n  z\n}\n");
118    }
119
120    #[test]
121    fn trim_ws() {
122        let mut s = Source::default();
123        s.push_str(
124            "function() {
125                x
126        }",
127        );
128        assert_eq!(s.s, "function() {\n  x\n}");
129    }
130}
wasmtime_wit_bindgen/source.rs

wasmtime_wit_bindgen/
source.rs
