feat: add option that allows instrument to exit on error

index.js

@@ -1,3 +1,5 @@
+'use strict'
+
 /* global __coverage__ */
 
 const arrify = require('arrify')
@@ -268,25 +270,27 @@ NYC.prototype._maybeInstrumentSource = function (code, filename, relFile) {
 }
 
 NYC.prototype._transformFactory = function (cacheDir) {
-  var _this = this
-  var instrumenter = this.instrumenter()
-  var instrumented
+  const instrumenter = this.instrumenter()
+  let instrumented
 
-  return function (code, metadata, hash) {
-    var filename = metadata.filename
-    var sourceMap = null
+  return (code, metadata, hash) => {
+    const filename = metadata.filename
+    let sourceMap = null
 
-    if (_this._sourceMap) sourceMap = _this.sourceMaps.extractAndRegister(code, filename, hash)
+    if (this._sourceMap) sourceMap = this.sourceMaps.extractAndRegister(code, filename, hash)
 
     try {
       instrumented = instrumenter.instrumentSync(code, filename, sourceMap)
     } catch (e) {
-      // don't fail external tests due to instrumentation bugs.
       debugLog('failed to instrument ' + filename + 'with error: ' + e.stack)
-      instrumented = code
+      if (this.config.exitOnError) {
+        process.exit(1)
+      } else {
+        instrumented = code
+      }
     }
 
-    if (_this.fakeRequire) {
+    if (this.fakeRequire) {
       return 'function x () {}'
     } else {
       return instrumented

lib/commands/instrument.js

@@ -46,6 +46,11 @@ exports.builder = function (yargs) {
       type: 'boolean',
       description: 'should nyc handle instrumentation?'
     })
+    .option('exit-on-error', {
+      default: false,
+      type: 'boolean',
+      description: 'should nyc exit when an instrumentation failure occurs?'
+    })
     .example('$0 instrument ./lib ./output', 'instrument all .js files in ./lib with coverage and output in ./output')
 }
 
@@ -62,7 +67,8 @@ exports.handler = function (argv) {
     extension: argv.extension,
     require: argv.require,
     compact: argv.compact,
-    preserveComments: argv.preserveComments
+    preserveComments: argv.preserveComments,
+    exitOnError: argv.exitOnError
   })
 
   nyc.instrumentAllFiles(argv.input, argv.output, function (err) {

test/fixtures/cli/subdir/input-dir/bad.js

@@ -0,0 +1 @@
+generate async futurelet console.log('Hello, World!') // this isn't real JS.

test/nyc-bin.js

@@ -1,4 +1,4 @@
-/* global describe, it */
+/* global describe, it, beforeEach */
 
 const _ = require('lodash')
 const path = require('path')
@@ -425,6 +425,10 @@ describe('the nyc cli', function () {
   })
 
   describe('instrument', function () {
+    beforeEach(() => {
+      rimraf.sync(path.resolve(fixturesCLI, 'subdir', 'output-dir'))
+    })
+
     describe('no output folder', function () {
       it('allows a single file to be instrumented', function (done) {
         var args = [bin, 'instrument', './half-covered.js']
@@ -485,6 +489,27 @@ describe('the nyc cli', function () {
           done()
         })
       })
+
+      it('can be configured to exit on error', function (done) {
+        var args = [
+          bin,
+          'instrument',
+          '--exit-on-error',
+          './input-dir',
+          './output-dir'
+        ]
+
+        var subdir = path.resolve(fixturesCLI, 'subdir')
+        var proc = spawn(process.execPath, args, {
+          cwd: subdir,
+          env: env
+        })
+
+        proc.on('exit', function (code) {
+          code.should.equal(1)
+          done()
+        })
+      })
     })
 
     describe('output folder specified', function () {