feat: respect node:coverage comments (#252)

This respects the `node:coverage` comments as used by the node:test
coverage reporter.

- `node:coverage disable` -> `c8 ignore start`
- `node:coverage enable` -> `c8 ignore stop`
- `node:coverage ignore next` -> `c8 ignore ignore next`
- `node:coverage ignore next N` -> `c8 ignore ignore next N`

lib/source.js

@@ -52,17 +52,17 @@ module.exports = class CovSource {
    * @return {{count?: number, start?: boolean, stop?: boolean}|undefined}
    */
   _parseIgnore (lineStr) {
-    const testIgnoreNextLines = lineStr.match(/^\W*\/\* [c|v]8 ignore next (?<count>[0-9]+)/)
+    const testIgnoreNextLines = lineStr.match(/^\W*\/\* (?:[cv]8|node:coverage) ignore next (?<count>[0-9]+)/)
     if (testIgnoreNextLines) {
       return { count: Number(testIgnoreNextLines.groups.count) }
     }
 
     // Check if comment is on its own line.
-    if (lineStr.match(/^\W*\/\* [c|v]8 ignore next/)) {
+    if (lineStr.match(/^\W*\/\* (?:[cv]8|node:coverage) ignore next/)) {
       return { count: 1 }
     }
 
-    if (lineStr.match(/\/\* [c|v]8 ignore next/)) {
+    if (lineStr.match(/\/\* ([cv]8|node:coverage) ignore next/)) {
       // Won't ignore successive lines, but the current line will be ignored.
       return { count: 0 }
     }
@@ -72,6 +72,12 @@ module.exports = class CovSource {
       if (testIgnoreStartStop.groups.mode === 'start') return { start: true }
       if (testIgnoreStartStop.groups.mode === 'stop') return { stop: true }
     }
+
+    const testNodeIgnoreStartStop = lineStr.match(/\/\* node:coverage (?<mode>enable|disable)/)
+    if (testNodeIgnoreStartStop) {
+      if (testNodeIgnoreStartStop.groups.mode === 'disable') return { start: true }
+      if (testNodeIgnoreStartStop.groups.mode === 'enable') return { stop: true }
+    }
   }
 
   // given a start column and end column in absolute offsets within
@@ -235,12 +241,14 @@ function originalPositionTryBoth (sourceMap, line, column) {
 // Not required since Node 12, see: https://github.com/nodejs/node/pull/27375
 const isPreNode12 = /^v1[0-1]\./u.test(process.version)
 function getShebangLength (source) {
+  /* c8 ignore start - platform-specific */
   if (isPreNode12 && source.indexOf('#!') === 0) {
     const match = source.match(/(?<shebang>#!.*)/)
     if (match) {
       return match.groups.shebang.length
     }
   } else {
+  /* c8 ignore stop - platform-specific */
     return 0
   }
 }

test/source.js

@@ -169,4 +169,102 @@ describe('Source', () => {
       })
     })
   }
+
+  describe('ignore hint using node:coverage', () => {
+    it('ignores the next line if /* node:coverage ignore next */ is on its own line', () => {
+      const sourceRaw = `
+      const a = 33
+      /* node:coverage ignore next */
+      const a = 99
+      `
+      const source = new CovSource(sourceRaw, 0)
+      source.lines[1].ignore.should.equal(false)
+      source.lines[2].ignore.should.equal(true)
+      source.lines[3].ignore.should.equal(true)
+    })
+
+    it('ignores the next N lines if /* node:coverage ignore next N */ is used', () => {
+      const sourceRaw = `
+      /* node:coverage ignore next 2 */
+      const a = 33
+      const a = 99
+      `
+      const source = new CovSource(sourceRaw, 0)
+      source.lines[1].ignore.should.equal(true)
+      source.lines[2].ignore.should.equal(true)
+      source.lines[3].ignore.should.equal(true)
+    })
+
+    it('ignores a line that contains /* node:coverage ignore next */', () => {
+      const sourceRaw = `
+      const a = foo ? true /* node:coverage ignore next */ : false
+      const b = 99
+      `
+      const source = new CovSource(sourceRaw, 0)
+      source.lines[1].ignore.should.equal(true)
+      source.lines[2].ignore.should.equal(false)
+    })
+
+    it('ignores lines between disable and enable', () => {
+      const sourceRaw = `
+      /* node:coverage disable */
+      function ignoreMe() {
+        // ...
+      }
+      /* node:coverage enable */
+
+      function doNotIgnoreMe() {
+        // ...
+      }
+      `
+      const source = new CovSource(sourceRaw, 0)
+      source.lines[1].ignore.should.equal(true)
+      source.lines[2].ignore.should.equal(true)
+      source.lines[3].ignore.should.equal(true)
+      source.lines[4].ignore.should.equal(true)
+      source.lines[5].ignore.should.equal(true)
+      source.lines[6].ignore.should.equal(false)
+      source.lines[7].ignore.should.equal(false)
+      source.lines[8].ignore.should.equal(false)
+      source.lines[9].ignore.should.equal(false)
+    })
+
+    it('ignore hint accepts other text content', () => {
+      const sourceRaw = `
+      const a = 33
+
+      /* node:coverage ignore next -- reasoning why this is ignored */
+      const b = 99
+
+      /* node:coverage disable: reasoning here */
+      function ignoreMe() {
+        // ...
+      }
+      /* node:coverage enable -- @preserve */
+
+      const c = a ? true /* node:coverage ignore next reasoning here */ : false
+
+      /* node:coverage ignore next 2 -- ignores next two lines */
+      const a = 33
+      const a = 99
+      `
+      const source = new CovSource(sourceRaw, 0)
+      source.lines[1].ignore.should.equal(false)
+      source.lines[2].ignore.should.equal(false)
+      source.lines[3].ignore.should.equal(true)
+      source.lines[4].ignore.should.equal(true)
+      source.lines[5].ignore.should.equal(false)
+      source.lines[6].ignore.should.equal(true)
+      source.lines[7].ignore.should.equal(true)
+      source.lines[8].ignore.should.equal(true)
+      source.lines[9].ignore.should.equal(true)
+      source.lines[10].ignore.should.equal(true)
+      source.lines[11].ignore.should.equal(false)
+      source.lines[12].ignore.should.equal(true)
+      source.lines[13].ignore.should.equal(false)
+      source.lines[14].ignore.should.equal(true)
+      source.lines[15].ignore.should.equal(true)
+      source.lines[16].ignore.should.equal(true)
+    })
+  })
 })