fix(coverage): merge coverage ranges (#13334)

Covered ranges were not merged and thus it appeared that some lines
might be uncovered. To fix this I used "v8-coverage" that takes care
of merging the ranges properly. With this change, coverage collected
from a file by multiple entrypoints is now correctly calculated.

I ended up forking https://github.com/demurgos/v8-coverage and adding
"cli/tools/coverage/merge.rs" and "cli/tools/coverage/range_tree.rs".

Cargo.lock

@@ -708,6 +708,7 @@ dependencies = [
  "tokio",
  "trust-dns-client",
  "trust-dns-server",
+ "typed-arena",
  "uuid",
  "walkdir",
  "winapi 0.3.9",

cli/Cargo.toml

@@ -83,6 +83,7 @@ tempfile = "=3.2.0"
 text-size = "=1.1.0"
 text_lines = "=0.4.1"
 tokio = { version = "=1.14", features = ["full"] }
+typed-arena = "2.0.1"
 uuid = { version = "=0.8.2", features = ["v4", "serde"] }
 walkdir = "=2.3.2"
 

cli/tests/integration/coverage_tests.rs

@@ -97,3 +97,83 @@ fn run_coverage_text(test_name: &str, extension: &str) {
 
   assert!(output.status.success());
 }
+
+#[test]
+fn multifile_coverage() {
+  let deno_dir = TempDir::new().expect("tempdir fail");
+  let tempdir = TempDir::new().expect("tempdir fail");
+  let tempdir = tempdir.path().join("cov");
+
+  let status = util::deno_cmd_with_deno_dir(deno_dir.path())
+    .current_dir(util::testdata_path())
+    .arg("test")
+    .arg("--quiet")
+    .arg("--unstable")
+    .arg(format!("--coverage={}", tempdir.to_str().unwrap()))
+    .arg("coverage/multifile/")
+    .stdout(std::process::Stdio::piped())
+    .stderr(std::process::Stdio::inherit())
+    .status()
+    .expect("failed to spawn test runner");
+
+  assert!(status.success());
+
+  let output = util::deno_cmd_with_deno_dir(deno_dir.path())
+    .current_dir(util::testdata_path())
+    .arg("coverage")
+    .arg("--unstable")
+    .arg(format!("{}/", tempdir.to_str().unwrap()))
+    .stdout(std::process::Stdio::piped())
+    .stderr(std::process::Stdio::piped())
+    .output()
+    .expect("failed to spawn coverage reporter");
+
+  // Verify there's no "Check" being printed
+  assert!(output.stderr.is_empty());
+
+  let actual =
+    util::strip_ansi_codes(std::str::from_utf8(&output.stdout).unwrap())
+      .to_string();
+
+  let expected = fs::read_to_string(
+    util::testdata_path().join("coverage/multifile/expected.out"),
+  )
+  .unwrap();
+
+  if !util::wildcard_match(&expected, &actual) {
+    println!("OUTPUT\n{}\nOUTPUT", actual);
+    println!("EXPECTED\n{}\nEXPECTED", expected);
+    panic!("pattern match failed");
+  }
+
+  assert!(output.status.success());
+
+  let output = util::deno_cmd_with_deno_dir(deno_dir.path())
+    .current_dir(util::testdata_path())
+    .arg("coverage")
+    .arg("--quiet")
+    .arg("--unstable")
+    .arg("--lcov")
+    .arg(format!("{}/", tempdir.to_str().unwrap()))
+    .stdout(std::process::Stdio::piped())
+    .stderr(std::process::Stdio::inherit())
+    .output()
+    .expect("failed to spawn coverage reporter");
+
+  let actual =
+    util::strip_ansi_codes(std::str::from_utf8(&output.stdout).unwrap())
+      .to_string();
+
+  let expected = fs::read_to_string(
+    util::testdata_path().join("coverage/multifile/expected.lcov"),
+  )
+  .unwrap();
+
+  if !util::wildcard_match(&expected, &actual) {
+    println!("OUTPUT\n{}\nOUTPUT", actual);
+    println!("EXPECTED\n{}\nEXPECTED", expected);
+    panic!("pattern match failed");
+  }
+
+  assert!(output.status.success());
+}

cli/tests/testdata/coverage/multifile/a_test.js

@@ -0,0 +1,8 @@
+import { test } from "./mod.js";
+
+Deno.test({
+  name: "bugrepo a",
+  fn: () => {
+    test(true);
+  },
+});

cli/tests/testdata/coverage/multifile/b_test.js

@@ -0,0 +1,8 @@
+import { test } from "./mod.js";
+
+Deno.test({
+  name: "bugrepo b",
+  fn: () => {
+    test(false);
+  },
+});

cli/tests/testdata/coverage/multifile/expected.lcov

@@ -0,0 +1,18 @@
+SF:[WILDCARD]mod.js
+FN:1,test
+FNDA:2,test
+FNF:1
+FNH:1
+BRDA:2,1,0,1
+BRF:1
+BRH:1
+DA:1,2
+DA:2,4
+DA:3,5
+DA:4,5
+DA:5,5
+DA:6,4
+DA:7,1
+LH:7
+LF:7
+end_of_record

cli/tests/testdata/coverage/multifile/expected.out

@@ -0,0 +1 @@
+cover [WILDCARD]/multifile/mod.js ... 100.000% (7/7)

cli/tests/testdata/coverage/multifile/mod.js

@@ -0,0 +1,6 @@
+export function test(a) {
+  if (a) {
+    return 0;
+  }
+  return 1;
+}

cli/tools/coverage/json_types.rs

@@ -0,0 +1,58 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use serde::Deserialize;
+use serde::Serialize;
+
+#[derive(Debug, Eq, PartialEq, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct CoverageRange {
+  /// Start byte index.
+  pub start_offset: usize,
+  /// End byte index.
+  pub end_offset: usize,
+  pub count: i64,
+}
+
+#[derive(Debug, Eq, PartialEq, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct FunctionCoverage {
+  pub function_name: String,
+  pub ranges: Vec<CoverageRange>,
+  pub is_block_coverage: bool,
+}
+
+#[derive(Debug, Eq, PartialEq, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct ScriptCoverage {
+  pub script_id: String,
+  pub url: String,
+  pub functions: Vec<FunctionCoverage>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct StartPreciseCoverageParameters {
+  pub call_count: bool,
+  pub detailed: bool,
+  pub allow_triggered_updates: bool,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct StartPreciseCoverageReturnObject {
+  pub timestamp: f64,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct TakePreciseCoverageReturnObject {
+  pub result: Vec<ScriptCoverage>,
+  pub timestamp: f64,
+}
+
+// TODO(bartlomieju): remove me
+#[derive(Eq, PartialEq, Clone, Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ProcessCoverage {
+  pub result: Vec<ScriptCoverage>,
+}

cli/tools/coverage/merge.rs

@@ -0,0 +1,840 @@
+// Forked from https://github.com/demurgos/v8-coverage/tree/d0ca18da8740198681e0bc68971b0a6cdb11db3e/rust
+// Copyright 2021 Charles Samborski. All rights reserved. MIT license.
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use super::json_types::CoverageRange;
+use super::json_types::FunctionCoverage;
+use super::json_types::ProcessCoverage;
+use super::json_types::ScriptCoverage;
+use super::range_tree::RangeTree;
+use super::range_tree::RangeTreeArena;
+use std::collections::BTreeMap;
+use std::collections::BTreeSet;
+use std::collections::HashMap;
+use std::iter::Peekable;
+
+pub fn merge_processes(
+  mut processes: Vec<ProcessCoverage>,
+) -> Option<ProcessCoverage> {
+  if processes.len() <= 1 {
+    return processes.pop();
+  }
+  let mut url_to_scripts: BTreeMap<String, Vec<ScriptCoverage>> =
+    BTreeMap::new();
+  for process_cov in processes {
+    for script_cov in process_cov.result {
+      url_to_scripts
+        .entry(script_cov.url.clone())
+        .or_insert_with(Vec::new)
+        .push(script_cov);
+    }
+  }
+
+  let result: Vec<ScriptCoverage> = url_to_scripts
+    .into_iter()
+    .enumerate()
+    .map(|(script_id, (_, scripts))| (script_id, scripts))
+    .map(|(script_id, scripts)| {
+      let mut merged: ScriptCoverage = merge_scripts(scripts.to_vec()).unwrap();
+      merged.script_id = script_id.to_string();
+      merged
+    })
+    .collect();
+
+  Some(ProcessCoverage { result })
+}
+
+pub fn merge_scripts(
+  mut scripts: Vec<ScriptCoverage>,
+) -> Option<ScriptCoverage> {
+  if scripts.len() <= 1 {
+    return scripts.pop();
+  }
+  let (script_id, url) = {
+    let first: &ScriptCoverage = &scripts[0];
+    (first.script_id.clone(), first.url.clone())
+  };
+  let mut range_to_funcs: BTreeMap<Range, Vec<FunctionCoverage>> =
+    BTreeMap::new();
+  for script_cov in scripts {
+    for func_cov in script_cov.functions {
+      let root_range = {
+        let root_range_cov: &CoverageRange = &func_cov.ranges[0];
+        Range {
+          start: root_range_cov.start_offset,
+          end: root_range_cov.end_offset,
+        }
+      };
+      range_to_funcs
+        .entry(root_range)
+        .or_insert_with(Vec::new)
+        .push(func_cov);
+    }
+  }
+
+  let functions: Vec<FunctionCoverage> = range_to_funcs
+    .into_iter()
+    .map(|(_, funcs)| merge_functions(funcs).unwrap())
+    .collect();
+
+  Some(ScriptCoverage {
+    script_id,
+    url,
+    functions,
+  })
+}
+
+#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)]
+struct Range {
+  start: usize,
+  end: usize,
+}
+
+impl Ord for Range {
+  fn cmp(&self, other: &Self) -> ::std::cmp::Ordering {
+    if self.start != other.start {
+      self.start.cmp(&other.start)
+    } else {
+      other.end.cmp(&self.end)
+    }
+  }
+}
+
+impl PartialOrd for Range {
+  fn partial_cmp(&self, other: &Self) -> Option<::std::cmp::Ordering> {
+    if self.start != other.start {
+      self.start.partial_cmp(&other.start)
+    } else {
+      other.end.partial_cmp(&self.end)
+    }
+  }
+}
+
+pub fn merge_functions(
+  mut funcs: Vec<FunctionCoverage>,
+) -> Option<FunctionCoverage> {
+  if funcs.len() <= 1 {
+    return funcs.pop();
+  }
+  let function_name = funcs[0].function_name.clone();
+  let rta_capacity: usize =
+    funcs.iter().fold(0, |acc, func| acc + func.ranges.len());
+  let rta = RangeTreeArena::with_capacity(rta_capacity);
+  let mut trees: Vec<&mut RangeTree> = Vec::new();
+  for func in funcs {
+    if let Some(tree) = RangeTree::from_sorted_ranges(&rta, &func.ranges) {
+      trees.push(tree);
+    }
+  }
+  let merged =
+    RangeTree::normalize(&rta, merge_range_trees(&rta, trees).unwrap());
+  let ranges = merged.to_ranges();
+  let is_block_coverage: bool = !(ranges.len() == 1 && ranges[0].count == 0);
+
+  Some(FunctionCoverage {
+    function_name,
+    ranges,
+    is_block_coverage,
+  })
+}
+
+fn merge_range_trees<'a>(
+  rta: &'a RangeTreeArena<'a>,
+  mut trees: Vec<&'a mut RangeTree<'a>>,
+) -> Option<&'a mut RangeTree<'a>> {
+  if trees.len() <= 1 {
+    return trees.pop();
+  }
+  let (start, end) = {
+    let first = &trees[0];
+    (first.start, first.end)
+  };
+  let delta: i64 = trees.iter().fold(0, |acc, tree| acc + tree.delta);
+  let children = merge_range_tree_children(rta, trees);
+
+  Some(rta.alloc(RangeTree::new(start, end, delta, children)))
+}
+
+struct StartEvent<'a> {
+  offset: usize,
+  trees: Vec<(usize, &'a mut RangeTree<'a>)>,
+}
+
+fn into_start_events<'a>(trees: Vec<&'a mut RangeTree<'a>>) -> Vec<StartEvent> {
+  let mut result: BTreeMap<usize, Vec<(usize, &'a mut RangeTree<'a>)>> =
+    BTreeMap::new();
+  for (parent_index, tree) in trees.into_iter().enumerate() {
+    for child in tree.children.drain(..) {
+      result
+        .entry(child.start)
+        .or_insert_with(Vec::new)
+        .push((parent_index, child));
+    }
+  }
+  result
+    .into_iter()
+    .map(|(offset, trees)| StartEvent { offset, trees })
+    .collect()
+}
+
+struct StartEventQueue<'a> {
+  pending: Option<StartEvent<'a>>,
+  queue: Peekable<::std::vec::IntoIter<StartEvent<'a>>>,
+}
+
+impl<'a> StartEventQueue<'a> {
+  pub fn new(queue: Vec<StartEvent<'a>>) -> StartEventQueue<'a> {
+    StartEventQueue {
+      pending: None,
+      queue: queue.into_iter().peekable(),
+    }
+  }
+
+  pub(crate) fn set_pending_offset(&mut self, offset: usize) {
+    self.pending = Some(StartEvent {
+      offset,
+      trees: Vec::new(),
+    });
+  }
+
+  pub(crate) fn push_pending_tree(
+    &mut self,
+    tree: (usize, &'a mut RangeTree<'a>),
+  ) {
+    self.pending = self.pending.take().map(|mut start_event| {
+      start_event.trees.push(tree);
+      start_event
+    });
+  }
+}
+
+impl<'a> Iterator for StartEventQueue<'a> {
+  type Item = StartEvent<'a>;
+
+  fn next(&mut self) -> Option<<Self as Iterator>::Item> {
+    let pending_offset: Option<usize> = match &self.pending {
+      Some(ref start_event) if !start_event.trees.is_empty() => {
+        Some(start_event.offset)
+      }
+      _ => None,
+    };
+
+    match pending_offset {
+      Some(pending_offset) => {
+        let queue_offset =
+          self.queue.peek().map(|start_event| start_event.offset);
+        match queue_offset {
+          None => self.pending.take(),
+          Some(queue_offset) => {
+            if pending_offset < queue_offset {
+              self.pending.take()
+            } else {
+              let mut result = self.queue.next().unwrap();
+              if pending_offset == queue_offset {
+                let pending_trees = self.pending.take().unwrap().trees;
+                result.trees.extend(pending_trees.into_iter())
+              }
+              Some(result)
+            }
+          }
+        }
+      }
+      None => self.queue.next(),
+    }
+  }
+}
+
+fn merge_range_tree_children<'a>(
+  rta: &'a RangeTreeArena<'a>,
+  parent_trees: Vec<&'a mut RangeTree<'a>>,
+) -> Vec<&'a mut RangeTree<'a>> {
+  let mut flat_children: Vec<Vec<&'a mut RangeTree<'a>>> =
+    Vec::with_capacity(parent_trees.len());
+  let mut wrapped_children: Vec<Vec<&'a mut RangeTree<'a>>> =
+    Vec::with_capacity(parent_trees.len());
+  let mut open_range: Option<Range> = None;
+
+  for _parent_tree in parent_trees.iter() {
+    flat_children.push(Vec::new());
+    wrapped_children.push(Vec::new());
+  }
+
+  let mut start_event_queue =
+    StartEventQueue::new(into_start_events(parent_trees));
+
+  let mut parent_to_nested: HashMap<usize, Vec<&'a mut RangeTree<'a>>> =
+    HashMap::new();
+
+  while let Some(event) = start_event_queue.next() {
+    open_range = if let Some(open_range) = open_range {
+      if open_range.end <= event.offset {
+        for (parent_index, nested) in parent_to_nested {
+          wrapped_children[parent_index].push(rta.alloc(RangeTree::new(
+            open_range.start,
+            open_range.end,
+            0,
+            nested,
+          )));
+        }
+        parent_to_nested = HashMap::new();
+        None
+      } else {
+        Some(open_range)
+      }
+    } else {
+      None
+    };
+
+    match open_range {
+      Some(open_range) => {
+        for (parent_index, tree) in event.trees {
+          let child = if tree.end > open_range.end {
+            let (left, right) = RangeTree::split(rta, tree, open_range.end);
+            start_event_queue.push_pending_tree((parent_index, right));
+            left
+          } else {
+            tree
+          };
+          parent_to_nested
+            .entry(parent_index)
+            .or_insert_with(Vec::new)
+            .push(child);
+        }
+      }
+      None => {
+        let mut open_range_end: usize = event.offset + 1;
+        for (_, ref tree) in &event.trees {
+          open_range_end = if tree.end > open_range_end {
+            tree.end
+          } else {
+            open_range_end
+          };
+        }
+        for (parent_index, tree) in event.trees {
+          if tree.end == open_range_end {
+            flat_children[parent_index].push(tree);
+            continue;
+          }
+          parent_to_nested
+            .entry(parent_index)
+            .or_insert_with(Vec::new)
+            .push(tree);
+        }
+        start_event_queue.set_pending_offset(open_range_end);
+        open_range = Some(Range {
+          start: event.offset,
+          end: open_range_end,
+        });
+      }
+    }
+  }
+  if let Some(open_range) = open_range {
+    for (parent_index, nested) in parent_to_nested {
+      wrapped_children[parent_index].push(rta.alloc(RangeTree::new(
+        open_range.start,
+        open_range.end,
+        0,
+        nested,
+      )));
+    }
+  }
+
+  let child_forests: Vec<Vec<&'a mut RangeTree<'a>>> = flat_children
+    .into_iter()
+    .zip(wrapped_children.into_iter())
+    .map(|(flat, wrapped)| merge_children_lists(flat, wrapped))
+    .collect();
+
+  let events = get_child_events_from_forests(&child_forests);
+
+  let mut child_forests: Vec<
+    Peekable<::std::vec::IntoIter<&'a mut RangeTree<'a>>>,
+  > = child_forests
+    .into_iter()
+    .map(|forest| forest.into_iter().peekable())
+    .collect();
+
+  let mut result: Vec<&'a mut RangeTree<'a>> = Vec::new();
+  for event in events.iter() {
+    let mut matching_trees: Vec<&'a mut RangeTree<'a>> = Vec::new();
+    for (_parent_index, children) in child_forests.iter_mut().enumerate() {
+      let next_tree: Option<&'a mut RangeTree<'a>> = {
+        if children.peek().map_or(false, |tree| tree.start == *event) {
+          children.next()
+        } else {
+          None
+        }
+      };
+      if let Some(next_tree) = next_tree {
+        matching_trees.push(next_tree);
+      }
+    }
+    if let Some(merged) = merge_range_trees(rta, matching_trees) {
+      result.push(merged);
+    }
+  }
+
+  result
+}
+
+fn get_child_events_from_forests<'a>(
+  forests: &[Vec<&'a mut RangeTree<'a>>],
+) -> BTreeSet<usize> {
+  let mut event_set: BTreeSet<usize> = BTreeSet::new();
+  for forest in forests {
+    for tree in forest {
+      event_set.insert(tree.start);
+      event_set.insert(tree.end);
+    }
+  }
+  event_set
+}
+
+// TODO: itertools?
+// https://play.integer32.com/?gist=ad2cd20d628e647a5dbdd82e68a15cb6&version=stable&mode=debug&edition=2015
+fn merge_children_lists<'a>(
+  a: Vec<&'a mut RangeTree<'a>>,
+  b: Vec<&'a mut RangeTree<'a>>,
+) -> Vec<&'a mut RangeTree<'a>> {
+  let mut merged: Vec<&'a mut RangeTree<'a>> = Vec::new();
+  let mut a = a.into_iter();
+  let mut b = b.into_iter();
+  let mut next_a = a.next();
+  let mut next_b = b.next();
+  loop {
+    match (next_a, next_b) {
+      (Some(tree_a), Some(tree_b)) => {
+        if tree_a.start < tree_b.start {
+          merged.push(tree_a);
+          next_a = a.next();
+          next_b = Some(tree_b);
+        } else {
+          merged.push(tree_b);
+          next_a = Some(tree_a);
+          next_b = b.next();
+        }
+      }
+      (Some(tree_a), None) => {
+        merged.push(tree_a);
+        merged.extend(a);
+        break;
+      }
+      (None, Some(tree_b)) => {
+        merged.push(tree_b);
+        merged.extend(b);
+        break;
+      }
+      (None, None) => break,
+    }
+  }
+
+  merged
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+  //   use test_generator::test_resources;
+
+  #[test]
+  fn empty() {
+    let inputs: Vec<ProcessCoverage> = Vec::new();
+    let expected: Option<ProcessCoverage> = None;
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+
+  #[test]
+  fn two_flat_trees() {
+    let inputs: Vec<ProcessCoverage> = vec![
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![CoverageRange {
+              start_offset: 0,
+              end_offset: 9,
+              count: 1,
+            }],
+          }],
+        }],
+      },
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![CoverageRange {
+              start_offset: 0,
+              end_offset: 9,
+              count: 2,
+            }],
+          }],
+        }],
+      },
+    ];
+    let expected: Option<ProcessCoverage> = Some(ProcessCoverage {
+      result: vec![ScriptCoverage {
+        script_id: String::from("0"),
+        url: String::from("/lib.js"),
+        functions: vec![FunctionCoverage {
+          function_name: String::from("lib"),
+          is_block_coverage: true,
+          ranges: vec![CoverageRange {
+            start_offset: 0,
+            end_offset: 9,
+            count: 3,
+          }],
+        }],
+      }],
+    });
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+
+  #[test]
+  fn two_trees_with_matching_children() {
+    let inputs: Vec<ProcessCoverage> = vec![
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 10,
+              },
+              CoverageRange {
+                start_offset: 3,
+                end_offset: 6,
+                count: 1,
+              },
+            ],
+          }],
+        }],
+      },
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 20,
+              },
+              CoverageRange {
+                start_offset: 3,
+                end_offset: 6,
+                count: 2,
+              },
+            ],
+          }],
+        }],
+      },
+    ];
+    let expected: Option<ProcessCoverage> = Some(ProcessCoverage {
+      result: vec![ScriptCoverage {
+        script_id: String::from("0"),
+        url: String::from("/lib.js"),
+        functions: vec![FunctionCoverage {
+          function_name: String::from("lib"),
+          is_block_coverage: true,
+          ranges: vec![
+            CoverageRange {
+              start_offset: 0,
+              end_offset: 9,
+              count: 30,
+            },
+            CoverageRange {
+              start_offset: 3,
+              end_offset: 6,
+              count: 3,
+            },
+          ],
+        }],
+      }],
+    });
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+
+  #[test]
+  fn two_trees_with_partially_overlapping_children() {
+    let inputs: Vec<ProcessCoverage> = vec![
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 10,
+              },
+              CoverageRange {
+                start_offset: 2,
+                end_offset: 5,
+                count: 1,
+              },
+            ],
+          }],
+        }],
+      },
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 20,
+              },
+              CoverageRange {
+                start_offset: 4,
+                end_offset: 7,
+                count: 2,
+              },
+            ],
+          }],
+        }],
+      },
+    ];
+    let expected: Option<ProcessCoverage> = Some(ProcessCoverage {
+      result: vec![ScriptCoverage {
+        script_id: String::from("0"),
+        url: String::from("/lib.js"),
+        functions: vec![FunctionCoverage {
+          function_name: String::from("lib"),
+          is_block_coverage: true,
+          ranges: vec![
+            CoverageRange {
+              start_offset: 0,
+              end_offset: 9,
+              count: 30,
+            },
+            CoverageRange {
+              start_offset: 2,
+              end_offset: 5,
+              count: 21,
+            },
+            CoverageRange {
+              start_offset: 4,
+              end_offset: 5,
+              count: 3,
+            },
+            CoverageRange {
+              start_offset: 5,
+              end_offset: 7,
+              count: 12,
+            },
+          ],
+        }],
+      }],
+    });
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+
+  #[test]
+  fn two_trees_with_with_complementary_children_summing_to_the_same_count() {
+    let inputs: Vec<ProcessCoverage> = vec![
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 1,
+              },
+              CoverageRange {
+                start_offset: 1,
+                end_offset: 8,
+                count: 6,
+              },
+              CoverageRange {
+                start_offset: 1,
+                end_offset: 5,
+                count: 5,
+              },
+              CoverageRange {
+                start_offset: 5,
+                end_offset: 8,
+                count: 7,
+              },
+            ],
+          }],
+        }],
+      },
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 9,
+                count: 4,
+              },
+              CoverageRange {
+                start_offset: 1,
+                end_offset: 8,
+                count: 8,
+              },
+              CoverageRange {
+                start_offset: 1,
+                end_offset: 5,
+                count: 9,
+              },
+              CoverageRange {
+                start_offset: 5,
+                end_offset: 8,
+                count: 7,
+              },
+            ],
+          }],
+        }],
+      },
+    ];
+    let expected: Option<ProcessCoverage> = Some(ProcessCoverage {
+      result: vec![ScriptCoverage {
+        script_id: String::from("0"),
+        url: String::from("/lib.js"),
+        functions: vec![FunctionCoverage {
+          function_name: String::from("lib"),
+          is_block_coverage: true,
+          ranges: vec![
+            CoverageRange {
+              start_offset: 0,
+              end_offset: 9,
+              count: 5,
+            },
+            CoverageRange {
+              start_offset: 1,
+              end_offset: 8,
+              count: 14,
+            },
+          ],
+        }],
+      }],
+    });
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+
+  #[test]
+  fn merges_a_similar_sliding_chain_a_bc() {
+    let inputs: Vec<ProcessCoverage> = vec![
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 7,
+                count: 10,
+              },
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 4,
+                count: 1,
+              },
+            ],
+          }],
+        }],
+      },
+      ProcessCoverage {
+        result: vec![ScriptCoverage {
+          script_id: String::from("0"),
+          url: String::from("/lib.js"),
+          functions: vec![FunctionCoverage {
+            function_name: String::from("lib"),
+            is_block_coverage: true,
+            ranges: vec![
+              CoverageRange {
+                start_offset: 0,
+                end_offset: 7,
+                count: 20,
+              },
+              CoverageRange {
+                start_offset: 1,
+                end_offset: 6,
+                count: 11,
+              },
+              CoverageRange {
+                start_offset: 2,
+                end_offset: 5,
+                count: 2,
+              },
+            ],
+          }],
+        }],
+      },
+    ];
+    let expected: Option<ProcessCoverage> = Some(ProcessCoverage {
+      result: vec![ScriptCoverage {
+        script_id: String::from("0"),
+        url: String::from("/lib.js"),
+        functions: vec![FunctionCoverage {
+          function_name: String::from("lib"),
+          is_block_coverage: true,
+          ranges: vec![
+            CoverageRange {
+              start_offset: 0,
+              end_offset: 7,
+              count: 30,
+            },
+            CoverageRange {
+              start_offset: 0,
+              end_offset: 6,
+              count: 21,
+            },
+            CoverageRange {
+              start_offset: 1,
+              end_offset: 5,
+              count: 12,
+            },
+            CoverageRange {
+              start_offset: 2,
+              end_offset: 4,
+              count: 3,
+            },
+          ],
+        }],
+      }],
+    });
+
+    assert_eq!(merge_processes(inputs), expected);
+  }
+}

cli/tools/coverage/mod.rs

@@ -17,8 +17,6 @@ use deno_core::serde_json;
 use deno_core::url::Url;
 use deno_core::LocalInspectorSession;
 use regex::Regex;
-use serde::Deserialize;
-use serde::Serialize;
 use sourcemap::SourceMap;
 use std::fs;
 use std::fs::File;
@@ -28,52 +26,11 @@ use std::path::PathBuf;
 use text_lines::TextLines;
 use uuid::Uuid;
 
-#[derive(Debug, Serialize, Deserialize, Clone)]
+mod json_types;
-#[serde(rename_all = "camelCase")]
+mod merge;
-struct CoverageRange {
+mod range_tree;
-  /// Start byte index.
-  start_offset: usize,
-  /// End byte index.
-  end_offset: usize,
-  count: usize,
-}
 
-#[derive(Debug, Serialize, Deserialize, Clone)]
+use json_types::*;
-#[serde(rename_all = "camelCase")]
-struct FunctionCoverage {
-  function_name: String,
-  ranges: Vec<CoverageRange>,
-  is_block_coverage: bool,
-}
-
-#[derive(Debug, Serialize, Deserialize, Clone)]
-#[serde(rename_all = "camelCase")]
-struct ScriptCoverage {
-  script_id: String,
-  url: String,
-  functions: Vec<FunctionCoverage>,
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
-struct StartPreciseCoverageParameters {
-  call_count: bool,
-  detailed: bool,
-  allow_triggered_updates: bool,
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
-struct StartPreciseCoverageReturnObject {
-  timestamp: f64,
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
-struct TakePreciseCoverageReturnObject {
-  result: Vec<ScriptCoverage>,
-  timestamp: f64,
-}
 
 pub struct CoverageCollector {
   pub dir: PathBuf,
@@ -175,21 +132,21 @@ struct BranchCoverageItem {
   line_index: usize,
   block_number: usize,
   branch_number: usize,
-  taken: Option<usize>,
+  taken: Option<i64>,
   is_hit: bool,
 }
 
 struct FunctionCoverageItem {
   name: String,
   line_index: usize,
-  execution_count: usize,
+  execution_count: i64,
 }
 
 struct CoverageReport {
   url: ModuleSpecifier,
   named_functions: Vec<FunctionCoverageItem>,
   branches: Vec<BranchCoverageItem>,
-  found_lines: Vec<(usize, usize)>,
+  found_lines: Vec<(usize, i64)>,
 }
 
 fn generate_coverage_report(
@@ -353,7 +310,7 @@ fn generate_coverage_report(
           results.into_iter()
         })
         .flatten()
-        .collect::<Vec<(usize, usize)>>();
+        .collect::<Vec<(usize, i64)>>();
 
       found_lines.sort_unstable_by_key(|(index, _)| *index);
       // combine duplicated lines
@@ -369,7 +326,7 @@ fn generate_coverage_report(
         .into_iter()
         .enumerate()
         .map(|(index, count)| (index, count))
-        .collect::<Vec<(usize, usize)>>()
+        .collect::<Vec<(usize, i64)>>()
     };
 
   coverage_report
@@ -553,38 +510,7 @@ fn collect_coverages(
   for file_path in file_paths {
     let json = fs::read_to_string(file_path.as_path())?;
     let new_coverage: ScriptCoverage = serde_json::from_str(&json)?;
-
+    coverages.push(new_coverage);
-    let existing_coverage =
-      coverages.iter_mut().find(|x| x.url == new_coverage.url);
-
-    if let Some(existing_coverage) = existing_coverage {
-      for new_function in new_coverage.functions {
-        let existing_function = existing_coverage
-          .functions
-          .iter_mut()
-          .find(|x| x.function_name == new_function.function_name);
-
-        if let Some(existing_function) = existing_function {
-          for new_range in new_function.ranges {
-            let existing_range =
-              existing_function.ranges.iter_mut().find(|x| {
-                x.start_offset == new_range.start_offset
-                  && x.end_offset == new_range.end_offset
-              });
-
-            if let Some(existing_range) = existing_range {
-              existing_range.count += new_range.count;
-            } else {
-              existing_function.ranges.push(new_range);
-            }
-          }
-        } else {
-          existing_coverage.functions.push(new_function);
-        }
-      }
-    } else {
-      coverages.push(new_coverage);
-    }
   }
 
   coverages.sort_by_key(|k| k.url.clone());
@@ -632,6 +558,18 @@ pub async fn cover_files(
     coverage_flags.exclude,
   );
 
+  let proc_coverages: Vec<_> = script_coverages
+    .into_iter()
+    .map(|cov| ProcessCoverage { result: vec![cov] })
+    .collect();
+
+  let script_coverages = if let Some(c) = merge::merge_processes(proc_coverages)
+  {
+    c.result
+  } else {
+    vec![]
+  };
+
   let reporter_kind = if coverage_flags.lcov {
     CoverageReporterKind::Lcov
   } else {

cli/tools/coverage/range_tree.rs

@@ -0,0 +1,207 @@
+// Forked from https://github.com/demurgos/v8-coverage/tree/d0ca18da8740198681e0bc68971b0a6cdb11db3e/rust
+// Copyright 2021 Charles Samborski. All rights reserved. MIT license.
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+use super::json_types::CoverageRange;
+use std::iter::Peekable;
+use typed_arena::Arena;
+
+pub struct RangeTreeArena<'a>(Arena<RangeTree<'a>>);
+
+impl<'a> RangeTreeArena<'a> {
+  #[cfg(test)]
+  pub fn new() -> Self {
+    RangeTreeArena(Arena::new())
+  }
+
+  pub fn with_capacity(n: usize) -> Self {
+    RangeTreeArena(Arena::with_capacity(n))
+  }
+
+  #[allow(clippy::mut_from_ref)]
+  pub fn alloc(&'a self, value: RangeTree<'a>) -> &'a mut RangeTree<'a> {
+    self.0.alloc(value)
+  }
+}
+
+#[derive(Eq, PartialEq, Debug)]
+pub struct RangeTree<'a> {
+  pub start: usize,
+  pub end: usize,
+  pub delta: i64,
+  pub children: Vec<&'a mut RangeTree<'a>>,
+}
+
+impl<'rt> RangeTree<'rt> {
+  pub fn new<'a>(
+    start: usize,
+    end: usize,
+    delta: i64,
+    children: Vec<&'a mut RangeTree<'a>>,
+  ) -> RangeTree<'a> {
+    RangeTree {
+      start,
+      end,
+      delta,
+      children,
+    }
+  }
+
+  pub fn split<'a>(
+    rta: &'a RangeTreeArena<'a>,
+    tree: &'a mut RangeTree<'a>,
+    value: usize,
+  ) -> (&'a mut RangeTree<'a>, &'a mut RangeTree<'a>) {
+    let mut left_children: Vec<&'a mut RangeTree<'a>> = Vec::new();
+    let mut right_children: Vec<&'a mut RangeTree<'a>> = Vec::new();
+    for child in tree.children.iter_mut() {
+      if child.end <= value {
+        left_children.push(child);
+      } else if value <= child.start {
+        right_children.push(child);
+      } else {
+        let (left_child, right_child) = Self::split(rta, child, value);
+        left_children.push(left_child);
+        right_children.push(right_child);
+      }
+    }
+
+    let left = RangeTree::new(tree.start, value, tree.delta, left_children);
+    let right = RangeTree::new(value, tree.end, tree.delta, right_children);
+    (rta.alloc(left), rta.alloc(right))
+  }
+
+  pub fn normalize<'a>(
+    rta: &'a RangeTreeArena<'a>,
+    tree: &'a mut RangeTree<'a>,
+  ) -> &'a mut RangeTree<'a> {
+    tree.children = {
+      let mut children: Vec<&'a mut RangeTree<'a>> = Vec::new();
+      let mut chain: Vec<&'a mut RangeTree<'a>> = Vec::new();
+      for child in tree.children.drain(..) {
+        let is_chain_end: bool =
+          match chain.last().map(|tree| (tree.delta, tree.end)) {
+            Some((delta, chain_end)) => {
+              (delta, chain_end) != (child.delta, child.start)
+            }
+            None => false,
+          };
+        if is_chain_end {
+          let mut chain_iter = chain.drain(..);
+          let mut head: &'a mut RangeTree<'a> = chain_iter.next().unwrap();
+          for tree in chain_iter {
+            head.end = tree.end;
+            for sub_child in tree.children.drain(..) {
+              sub_child.delta += tree.delta - head.delta;
+              head.children.push(sub_child);
+            }
+          }
+          children.push(RangeTree::normalize(rta, head));
+        }
+        chain.push(child)
+      }
+      if !chain.is_empty() {
+        let mut chain_iter = chain.drain(..);
+        let mut head: &'a mut RangeTree<'a> = chain_iter.next().unwrap();
+        for tree in chain_iter {
+          head.end = tree.end;
+          for sub_child in tree.children.drain(..) {
+            sub_child.delta += tree.delta - head.delta;
+            head.children.push(sub_child);
+          }
+        }
+        children.push(RangeTree::normalize(rta, head));
+      }
+
+      if children.len() == 1
+        && children[0].start == tree.start
+        && children[0].end == tree.end
+      {
+        let normalized = children.remove(0);
+        normalized.delta += tree.delta;
+        return normalized;
+      }
+
+      children
+    };
+
+    tree
+  }
+
+  pub fn to_ranges(&self) -> Vec<CoverageRange> {
+    let mut ranges: Vec<CoverageRange> = Vec::new();
+    let mut stack: Vec<(&RangeTree, i64)> = vec![(self, 0)];
+    while let Some((cur, parent_count)) = stack.pop() {
+      let count: i64 = parent_count + cur.delta;
+      ranges.push(CoverageRange {
+        start_offset: cur.start,
+        end_offset: cur.end,
+        count,
+      });
+      for child in cur.children.iter().rev() {
+        stack.push((child, count))
+      }
+    }
+    ranges
+  }
+
+  pub fn from_sorted_ranges<'a>(
+    rta: &'a RangeTreeArena<'a>,
+    ranges: &[CoverageRange],
+  ) -> Option<&'a mut RangeTree<'a>> {
+    Self::from_sorted_ranges_inner(
+      rta,
+      &mut ranges.iter().peekable(),
+      ::std::usize::MAX,
+      0,
+    )
+  }
+
+  fn from_sorted_ranges_inner<'a, 'b, 'c: 'b>(
+    rta: &'a RangeTreeArena<'a>,
+    ranges: &'b mut Peekable<impl Iterator<Item = &'c CoverageRange>>,
+    parent_end: usize,
+    parent_count: i64,
+  ) -> Option<&'a mut RangeTree<'a>> {
+    let has_range: bool = match ranges.peek() {
+      None => false,
+      Some(range) => range.start_offset < parent_end,
+    };
+    if !has_range {
+      return None;
+    }
+    let range = ranges.next().unwrap();
+    let start: usize = range.start_offset;
+    let end: usize = range.end_offset;
+    let count: i64 = range.count;
+    let delta: i64 = count - parent_count;
+    let mut children: Vec<&mut RangeTree> = Vec::new();
+    while let Some(child) =
+      Self::from_sorted_ranges_inner(rta, ranges, end, count)
+    {
+      children.push(child);
+    }
+    Some(rta.alloc(RangeTree::new(start, end, delta, children)))
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn from_sorted_ranges_empty() {
+    let rta = RangeTreeArena::new();
+    let inputs: Vec<CoverageRange> = vec![CoverageRange {
+      start_offset: 0,
+      end_offset: 9,
+      count: 1,
+    }];
+    let actual: Option<&mut RangeTree> =
+      RangeTree::from_sorted_ranges(&rta, &inputs);
+    let expected: Option<&mut RangeTree> =
+      Some(rta.alloc(RangeTree::new(0, 9, 1, Vec::new())));
+
+    assert_eq!(actual, expected);
+  }
+}