feat: switch to using Node's built in coverage

README.md

@@ -1,6 +1,6 @@
-# c8 - native v8 code-coverage
+# c8 - native V8 code-coverage
 
-Code-coverage using [v8's Inspector](https://nodejs.org/dist/latest-v8.x/docs/api/inspector.html)
+Code-coverage using [V8's Inspector](https://nodejs.org/dist/latest-v8.x/docs/api/inspector.html)
 that's compatible with [Istanbul's reporters](https://istanbul.js.org/docs/advanced/alternative-reporters/).
 
 Like [nyc](https://github.com/istanbuljs/nyc), c8 just magically works:
@@ -10,20 +10,14 @@ npm i c8 -g
 c8 node foo.js
 ```
 
-The above example will collect coverage for `foo.js` using v8's inspector.
+The above example will collect coverage for `foo.js` using V8's inspector.
 
-## Disclaimer
-
-c8 uses bleeding edge v8 features (_it's an ongoing experiment, testing
-what will eventually be possible in the realm of test coverage in Node.js_).
+## c8 report
 
-For the best experience, try running with [a canary build of Node.js](https://github.com/v8/node).
+run `c8 report` to regenerate reports after `c8` has already been run.
 
-## How it Works
-
-Before running your application c8 creates [an inspector session](https://nodejs.org/api/inspector.html) in v8 and enables v8's
-[built in coverage reporting](https://v8project.blogspot.com/2017/12/javascript-code-coverage.html).
+## Disclaimer
 
-Just before your application exits, c8 fetches the coverage information from
-v8 and writes it to disk in a format compatible with
-[Istanbul's reporters](https://istanbul.js.org/).
+c8 uses
+[bleeding edge Node.js features](https://github.com/nodejs/node/pull/22527),
+make sure you're running Node.js `>= 10.10.0`.

bin/c8.js

@@ -4,31 +4,36 @@
 const foreground = require('foreground-child')
 const mkdirp = require('mkdirp')
 const report = require('../lib/report')
-const {resolve} = require('path')
 const rimraf = require('rimraf')
-const sw = require('spawn-wrap')
 const {
   hideInstrumenteeArgs,
   hideInstrumenterArgs,
   yargs
 } = require('../lib/parse-args')
 
 const instrumenterArgs = hideInstrumenteeArgs()
+let argv = yargs.parse(instrumenterArgs)
 
-const argv = yargs.parse(instrumenterArgs)
+if (argv._[0] === 'report') {
+  argv = yargs.parse(process.argv) // support flag arguments after "report".
+  outputReport()
+} else {
+  rimraf.sync(argv.tempDirectory)
+  mkdirp.sync(argv.tempDirectory)
+  process.env.NODE_V8_COVERAGE = argv.tempDirectory
 
-const tmpDirctory = resolve(argv.coverageDirectory, './tmp')
-rimraf.sync(tmpDirctory)
-mkdirp.sync(tmpDirctory)
-
-sw([require.resolve('../lib/wrap')], {
-  C8_ARGV: JSON.stringify(argv)
-})
+  foreground(hideInstrumenterArgs(argv), () => {
+    outputReport()
+  })
+}
 
-foreground(hideInstrumenterArgs(argv), (out) => {
+function outputReport () {
   report({
+    include: argv.include,
+    exclude: argv.exclude,
     reporter: Array.isArray(argv.reporter) ? argv.reporter : [argv.reporter],
-    coverageDirectory: argv.coverageDirectory,
-    watermarks: argv.watermarks
+    tempDirectory: argv.tempDirectory,
+    watermarks: argv.watermarks,
+    resolve: argv.resolve
   })
-})
+}

lib/parse-args.js

@@ -1,13 +1,13 @@
 const Exclude = require('test-exclude')
 const findUp = require('find-up')
-const {readFileSync} = require('fs')
+const { readFileSync } = require('fs')
 const yargs = require('yargs')
 const parser = require('yargs-parser')
 
 const configPath = findUp.sync(['.c8rc', '.c8rc.json'])
 const config = configPath ? JSON.parse(readFileSync(configPath)) : {}
 
-yargs
+yargs()
   .usage('$0 [opts] [script] [opts]')
   .option('reporter', {
     alias: 'r',
@@ -17,17 +17,26 @@ yargs
   .option('exclude', {
     alias: 'x',
     default: Exclude.defaultExclude,
-    describe: 'a list of specific files and directories that should be excluded from coverage, glob patterns are supported.'
+    describe: 'a list of specific files and directories that should be excluded from coverage (glob patterns are supported)'
   })
   .option('include', {
     alias: 'n',
     default: [],
-    describe: 'a list of specific files that should be covered, glob patterns are supported'
+    describe: 'a list of specific files that should be covered (glob patterns are supported)'
   })
   .option('coverage-directory', {
     default: './coverage',
     describe: 'directory to output coverage JSON and reports'
   })
+  .option('temp-directory', {
+    default: './coverage/tmp',
+    describe: 'directory V8 coverage data is written to and read from'
+  })
+  .option('resolve', {
+    default: '',
+    describe: 'resolve paths to alternate base directory'
+  })
+  .command('report', 'read V8 coverage data from temp and output report')
   .pkgConf('c8')
   .config(config)
   .demandCommand(1)

lib/report.js

@@ -1,14 +1,29 @@
+const Exclude = require('test-exclude')
 const libCoverage = require('istanbul-lib-coverage')
 const libReport = require('istanbul-lib-report')
 const reports = require('istanbul-reports')
-const {readdirSync, readFileSync} = require('fs')
-const {resolve} = require('path')
+const { readdirSync, readFileSync } = require('fs')
+const { resolve, isAbsolute } = require('path')
+const v8CoverageMerge = require('v8-coverage-merge')
+const v8toIstanbul = require('v8-to-istanbul')
 
 class Report {
-  constructor ({reporter, coverageDirectory, watermarks}) {
+  constructor ({
+    exclude,
+    include,
+    reporter,
+    tempDirectory,
+    watermarks,
+    resolve
+  }) {
     this.reporter = reporter
-    this.coverageDirectory = coverageDirectory
+    this.tempDirectory = tempDirectory
     this.watermarks = watermarks
+    this.resolve = resolve
+    this.exclude = Exclude({
+      exclude: exclude,
+      include: include
+    })
   }
   run () {
     const map = this._getCoverageMapFromAllCoverageFiles()
@@ -25,20 +40,39 @@ class Report {
   }
   _getCoverageMapFromAllCoverageFiles () {
     const map = libCoverage.createCoverageMap({})
+    const mergedResults = {}
+    this._loadReports().forEach((report) => {
+      report.result.forEach((result) => {
+        if (this.exclude.shouldInstrument(result.url) &&
+            isAbsolute(result.url)) {
+          if (mergedResults[result.url]) {
+            mergedResults[result.url] = v8CoverageMerge(
+              mergedResults[result.url],
+              result
+            )
+          } else {
+            mergedResults[result.url] = result
+          }
+        }
+      })
+    })
 
-    this._loadReports().forEach(function (report) {
-      map.merge(report)
+    Object.keys(mergedResults).forEach((url) => {
+      const result = mergedResults[url]
+      const path = resolve(this.resolve, result.url)
+      const script = v8toIstanbul(path)
+      script.applyCoverage(result.functions)
+      map.merge(script.toIstanbul())
     })
 
     return map
   }
   _loadReports () {
-    const tmpDirctory = resolve(this.coverageDirectory, './tmp')
-    const files = readdirSync(tmpDirctory)
+    const files = readdirSync(this.tempDirectory)
 
     return files.map((f) => {
       return JSON.parse(readFileSync(
-        resolve(tmpDirctory, f),
+        resolve(this.tempDirectory, f),
         'utf8'
       ))
     })