parity/
parity.rs

1//! Emits diffs as JSON so `tests/wasm.test.ts` can compare against the JS twin.
2//!
3//! Exists because a divergence between the two implementations is the worst bug
4//! this system can have: a user gets correct results on one path and wrong
5//! results on the other, with no signal telling them which they saw.
6
7use fc_diff::{diff_lines, diff_stats};
8
9fn main() {
10    let mut args = std::env::args().skip(1);
11    let before = args.next().unwrap_or_default();
12    let after = args.next().unwrap_or_default();
13
14    let lines = diff_lines(&before, &after);
15    let stats = diff_stats(&lines);
16
17    // Hand-rolled JSON: serde would pull `serde-wasm-bindgen` into a crate whose
18    // whole point is having no dependencies, and the shape is fixed anyway.
19    print!("{{\"added\":{},\"removed\":{},\"identical\":{},\"lines\":[", stats.added, stats.removed, stats.identical);
20    for (i, line) in lines.iter().enumerate() {
21        if i > 0 {
22            print!(",");
23        }
24        print!(
25            "{{\"kind\":{},\"text\":{},\"oldLine\":{},\"newLine\":{}}}",
26            json_str(line.kind.as_str()),
27            json_str(&line.text),
28            line.old_line.map(|n| n.to_string()).unwrap_or_else(|| "null".into()),
29            line.new_line.map(|n| n.to_string()).unwrap_or_else(|| "null".into()),
30        );
31    }
32    println!("]}}");
33}
34
35fn json_str(value: &str) -> String {
36    let mut out = String::with_capacity(value.len() + 2);
37    out.push('"');
38    for ch in value.chars() {
39        match ch {
40            '"' => out.push_str("\\\""),
41            '\\' => out.push_str("\\\\"),
42            '\n' => out.push_str("\\n"),
43            '\r' => out.push_str("\\r"),
44            '\t' => out.push_str("\\t"),
45            c if (c as u32) < 0x20 => out.push_str(&format!("\\u{:04x}", c as u32)),
46            c => out.push(c),
47        }
48    }
49    out.push('"');
50    out
51}
parity/parity.rs

parity/
parity.rs
