feat(coverage): add html reporter (#21495)

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

cli/tools/coverage/util.rs

@@ -0,0 +1,103 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::url::Url;
+
+pub fn find_root(urls: Vec<&Url>) -> Option<Url> {
+  if urls.is_empty() {
+    return None;
+  }
+
+  // Gets the common first part of all the urls.
+  let root = urls[0]
+    .as_ref()
+    .chars()
+    .enumerate()
+    .take_while(|(i, c)| {
+      urls.iter().all(|u| u.as_ref().chars().nth(*i) == Some(*c))
+    })
+    .map(|(_, c)| c)
+    .collect::<String>();
+
+  if let Some(index) = root.rfind('/') {
+    // Removes the basename part if exists.
+    Url::parse(&root[..index + 1]).ok()
+  } else {
+    Url::parse(&root).ok()
+  }
+}
+
+pub fn percent_to_class(percent: f32) -> &'static str {
+  match percent {
+    x if x < 50.0 => "low",
+    x if x < 80.0 => "medium",
+    _ => "high",
+  }
+}
+
+pub fn calc_coverage_display_info(
+  hit: usize,
+  miss: usize,
+) -> (usize, f32, &'static str) {
+  let total = hit + miss;
+  let percent = if total == 0 {
+    100.0
+  } else {
+    (hit as f32 / total as f32) * 100.0
+  };
+  let class = percent_to_class(percent);
+  (total, percent, class)
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_find_root() {
+    let urls = vec![
+      Url::parse("file:///a/b/c/d/e.ts").unwrap(),
+      Url::parse("file:///a/b/c/d/f.ts").unwrap(),
+      Url::parse("file:///a/b/c/d/g.ts").unwrap(),
+    ];
+    let urls = urls.iter().collect();
+    assert_eq!(find_root(urls), Url::parse("file:///a/b/c/d/").ok());
+  }
+
+  #[test]
+  fn test_find_root_empty() {
+    let urls = vec![];
+    assert_eq!(find_root(urls), None);
+  }
+
+  #[test]
+  fn test_find_root_with_similar_filenames() {
+    let urls = vec![
+      Url::parse("file:///a/b/c/d/foo0.ts").unwrap(),
+      Url::parse("file:///a/b/c/d/foo1.ts").unwrap(),
+      Url::parse("file:///a/b/c/d/foo2.ts").unwrap(),
+    ];
+    let urls = urls.iter().collect();
+    assert_eq!(find_root(urls), Url::parse("file:///a/b/c/d/").ok());
+  }
+
+  #[test]
+  fn test_find_root_with_similar_dirnames() {
+    let urls = vec![
+      Url::parse("file:///a/b/c/foo0/mod.ts").unwrap(),
+      Url::parse("file:///a/b/c/foo1/mod.ts").unwrap(),
+      Url::parse("file:///a/b/c/foo2/mod.ts").unwrap(),
+    ];
+    let urls = urls.iter().collect();
+    assert_eq!(find_root(urls), Url::parse("file:///a/b/c/").ok());
+  }
+
+  #[test]
+  fn test_percent_to_class() {
+    assert_eq!(percent_to_class(0.0), "low");
+    assert_eq!(percent_to_class(49.9), "low");
+    assert_eq!(percent_to_class(50.0), "medium");
+    assert_eq!(percent_to_class(79.9), "medium");
+    assert_eq!(percent_to_class(80.0), "high");
+    assert_eq!(percent_to_class(100.0), "high");
+  }
+}