fix(coverage): ignore comments (#8639)

This commit fixes coverage collection by ignoring
comments when tallying up line counts.

cli/tests/integration_tests.rs

@@ -3437,6 +3437,12 @@ itest!(deno_test_coverage {
   exit_code: 0,
 });
 
+itest!(deno_test_comment_coverage {
+  args: "test --coverage --unstable test_comment_coverage.ts",
+  output: "test_comment_coverage.out",
+  exit_code: 0,
+});
+
 itest!(deno_test_branch_coverage {
   args: "test --coverage --unstable test_branch_coverage.ts",
   output: "test_branch_coverage.out",

cli/tests/subdir/comment.ts

@@ -0,0 +1,4 @@
+// This is a comment.
+export function comment(): string {
+  return "comment";
+}

cli/tests/test_comment_coverage.out

@@ -0,0 +1,7 @@
+[WILDCARD]/tests/$deno$test.ts
+running 1 tests
+test comment ... ok ([WILDCARD])
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out ([WILDCARD])
+
+[WILDCARD]/tests/subdir/comment.ts ... 100.000% (4/4)

cli/tests/test_comment_coverage.ts

@@ -0,0 +1,5 @@
+import { comment } from "./subdir/comment.ts";
+
+Deno.test("comment", function () {
+  comment();
+});

cli/tools/coverage.rs

@@ -1,6 +1,9 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
+use crate::ast;
+use crate::ast::TokenOrComment;
 use crate::colors;
+use crate::media_type::MediaType;
 use crate::module_graph::TypeLib;
 use crate::program_state::ProgramState;
 use deno_core::error::AnyError;
@@ -15,6 +18,7 @@ use serde::Serialize;
 use std::fs;
 use std::path::PathBuf;
 use std::sync::Arc;
+use swc_common::Span;
 use uuid::Uuid;
 
 pub struct CoverageCollector {
@@ -127,8 +131,16 @@ impl PrettyCoverageReporter {
     script_coverage: &ScriptCoverage,
     script_source: &str,
   ) {
-    let lines = script_source.split('\n').collect::<Vec<_>>();
+    let mut ignored_spans: Vec<Span> = Vec::new();
+    for item in ast::lex("", script_source, &MediaType::JavaScript) {
+      if let TokenOrComment::Token(_) = item.inner {
+        continue;
+      }
 
+      ignored_spans.push(item.span);
+    }
+
+    let lines = script_source.split('\n').collect::<Vec<_>>();
     let mut covered_lines: Vec<usize> = Vec::new();
     let mut uncovered_lines: Vec<usize> = Vec::new();
 
@@ -138,6 +150,16 @@ impl PrettyCoverageReporter {
 
       let mut count = 0;
 
+      let ignore = ignored_spans.iter().any(|span| {
+        (span.lo.0 as usize) <= line_start_offset
+          && (span.hi.0 as usize) >= line_end_offset
+      });
+
+      if ignore {
+        covered_lines.push(index);
+        continue;
+      }
+
       // Count the hits of ranges that include the entire line which will always be at-least one
       // as long as the code has been evaluated.
       for function in &script_coverage.functions {