feat: playing around with initial implementation

.gitignore

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+.DS_Store
+node_modules

LICENSE.txt

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+Copyright (c) 2017, Contributors
+
+Permission to use, copy, modify, and/or distribute this software
+for any purpose with or without fee is hereby granted, provided
+that the above copyright notice and this permission notice
+appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE
+LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

README.md

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+# c8 - native code-coverage
+
+Code-coverage using [v8's Profiler](https://nodejs.org/dist/latest-v8.x/docs/api/inspector.html)
+compatible with [Istanbul's reporters](https://istanbul.js.org/docs/advanced/alternative-reporters/).
+
+Like [nyc](https://github.com/istanbuljs/nyc), c8 just magically works, simply:
+
+```bash
+npm i c8 -g
+c8 node foo.js
+```
+
+The above example will collect coverage for `foo.js` using v8's profiler.
+
+TODO:
+
+- [ ] write logic for converting v8 coverage output to [Istanbul Coverage.json format](https://github.com/gotwarlost/istanbul/blob/master/coverage.json.md).
+- [ ] talk to Node.js project about silencing messages:
+
+   > `Debugger listening on ws://127.0.0.1:56399/e850110a-c5df-41d8-8ef2-400f6829617f`.
+
+- [ ] figure out why `detailed` mode does not appear to be working.
+- [ ] figure out a better way to determine that all processes in event loop
+   have terminated (except the inspector session).

bin/c8.js

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+#!/usr/bin/env node
+
+const argv = require('yargs').parse()
+const foreground = require('foreground-child')
+const sw = require('spawn-wrap')
+
+if (argv._.length) {
+  sw([require.resolve('./wrap')])
+  foreground(process.argv.slice(2))
+}

bin/wrap.js

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+const fs = require('fs')
+const sw = require('spawn-wrap')
+const CRI = require('chrome-remote-interface');
+const getPort = require('get-port');
+const inspector = require('inspector')
+
+// if there are N or less active handles
+// in the event loop, dump coverage and exit.
+const EXIT_HANDLE_COUNT = 4
+
+getPort().then(async port => {
+  // start an inspector session on an unused port.
+  inspector.open(port, true)
+  const client = await CRI({port: port})
+  const {Profiler} = client
+  await Profiler.enable()
+  await Profiler.startPreciseCoverage({callCount: true, detailed: true})
+
+  // run the original "main" now that we've started the inspector.
+  sw.runMain()
+
+  // wait for everything in event loop to terminate
+  // except for inspector session.
+  setInterval(() => {
+    const handleCount = process._getActiveHandles().length
+      + process._getActiveRequests().length
+    if (handleCount <= EXIT_HANDLE_COUNT) {
+      outputCoverageAndExit(client, Profiler)
+    }
+  }, 100)
+}).catch(err => {
+  throw err
+})
+
+async function outputCoverageAndExit (client, Profiler) {
+  const IGNORED_PATHS = [
+    /\/bin\/wrap.js/,
+    /\/node_modules\//,
+    /node-spawn-wrap/
+  ]
+  let {result} = await Profiler.takePreciseCoverage()
+  result = result.filter(coverage => {
+    for (var ignored, i = 0; (ignored = IGNORED_PATHS[i]) !== undefined; i++) {
+      if (ignored.test(coverage.url)) return false
+    }
+    if (!/^\//.test(coverage.url)) return false
+    else return true
+  })
+  console.log(JSON.stringify(result, null, 2))
+  client.close()
+  process.exit(0)
+}