Ignore lines from code coverage which are not executable

index.js

@@ -1,5 +1,5 @@
 const V8ToIstanbul = require('./lib/v8-to-istanbul')
 
-module.exports = function (path, wrapperLength, sources, excludePath) {
-  return new V8ToIstanbul(path, wrapperLength, sources, excludePath)
+module.exports = function (path, wrapperLength, sources, excludePath, plugin) {
+  return new V8ToIstanbul(path, wrapperLength, sources, excludePath, plugin)
 }

lib/plugin.js

@@ -0,0 +1,36 @@
+const esbuild = require('esbuild')
+const vlq = require('vlq')
+
+module.exports = function (source, path) {
+  let result
+  try {
+    const loader = path.endsWith('.tsx') || path.endsWith('.jsx') ? { loader: 'tsx', jsx: 'preserve' } : {}
+    result = esbuild.transformSync(source.sourceRaw, {
+      sourcemap: 'external',
+      loader: 'ts',
+      minify: false,
+      minifyWhitespace: false,
+      minifySyntax: false,
+      legalComments: 'none',
+      ...loader
+    })
+  } catch (err) {
+    console.error(`${path} parsed with error ${err.message}`)
+    return
+  }
+  const mappings = JSON.parse(result.map).mappings
+  if (mappings) {
+    let start = 0
+    const executableLines = mappings.split(';').reduce((set, str) => {
+      start = str.split(',').reduce((number, seg) => {
+        const [, , line] = vlq.decode(seg)
+        set.add(number + line)
+        return number + line
+      }, start)
+      return set
+    }, new Set())
+    source.lines.forEach((line, index) => {
+      line.ignore = line.ignore || !executableLines.has(index)
+    })
+  }
+}

lib/source.js

@@ -4,6 +4,7 @@ const { originalPositionFor, generatedPositionFor, GREATEST_LOWER_BOUND, LEAST_U
 
 module.exports = class CovSource {
   constructor (sourceRaw, wrapperLength) {
+    this.sourceRaw = sourceRaw
     sourceRaw = sourceRaw ? sourceRaw.trimEnd() : ''
     this.lines = []
     this.eof = sourceRaw.length

lib/v8-to-istanbul.js

@@ -25,12 +25,13 @@ const isNode8 = /^v8\./.test(process.version)
 const cjsWrapperLength = isOlderNode10 ? require('module').wrapper[0].length : 0
 
 module.exports = class V8ToIstanbul {
-  constructor (scriptPath, wrapperLength, sources, excludePath) {
+  constructor (scriptPath, wrapperLength, sources, excludePath, plugin) {
     assert(typeof scriptPath === 'string', 'scriptPath must be a string')
     assert(!isNode8, 'This module does not support node 8 or lower, please upgrade to node 10')
     this.path = parsePath(scriptPath)
     this.wrapperLength = wrapperLength === undefined ? cjsWrapperLength : wrapperLength
     this.excludePath = excludePath || (() => false)
+    this.plugin = plugin
     this.sources = sources || {}
     this.generatedLines = []
     this.branches = {}
@@ -260,6 +261,10 @@ module.exports = class V8ToIstanbul {
       return
     }
 
+    if (this.plugin) {
+      this.plugin(source, resolvedPath)
+    }
+
     return {
       [resolvedPath]: {
         path: resolvedPath,
@@ -281,8 +286,11 @@ module.exports = class V8ToIstanbul {
       s: {}
     }
     source.lines.forEach((line, index) => {
+      if (line.ignore) {
+        return
+      }
       statements.statementMap[`${index}`] = line.toIstanbul()
-      statements.s[`${index}`] = line.ignore ? 1 : line.count
+      statements.s[`${index}`] = line.count
     })
     return statements
   }