Add produceSourceMap option

README.md

@@ -51,6 +51,15 @@ and a `text-lcov` coverage report.
 nyc --reporter=lcov --reporter=text-lcov npm test
 ```
 
+## Stack Traces
+
+When `source-map` handling enabled, then the instrumented source files will
+include inline source maps for the instrumenter transform. When combined with
+[source-map-support](https://github.com/evanw/node-source-map-support),
+stack traces for instrumented code should reflect the original lines.
+
+This is enabled by default, but may be disabled by `nyc --source-map=false`.
+
 ## Support for custom require hooks (babel, webpack, etc.)
 
 nyc supports custom require hooks like

index.js

@@ -15,6 +15,7 @@ var rimraf = require('rimraf')
 var onExit = require('signal-exit')
 var resolveFrom = require('resolve-from')
 var convertSourceMap = require('convert-source-map')
+var mergeSourceMap = require('merge-source-map')
 var md5hex = require('md5-hex')
 var findCacheDir = require('find-cache-dir')
 var js = require('default-require-extensions/js')
@@ -120,7 +121,9 @@ NYC.prototype.instrumenter = function () {
 }
 
 NYC.prototype._createInstrumenter = function () {
-  return this._instrumenterLib(this.cwd)
+  return this._instrumenterLib(this.cwd, {
+    produceSourceMap: this._sourceMap ? 'inline' : ''
+  })
 }
 
 NYC.prototype.addFile = function (filename) {
@@ -250,14 +253,30 @@ NYC.prototype._transformFactory = function (cacheDir) {
 
   return function (code, metadata, hash) {
     var filename = metadata.filename
+    var sourceMap
+
+    if (_this._sourceMap) {
+      sourceMap = convertSourceMap.fromSource(code) || convertSourceMap.fromMapFileSource(code, path.dirname(filename))
 
-    if (_this._sourceMap) _this._handleSourceMap(cacheDir, code, hash, filename)
+      _this._handleSourceMap(cacheDir, code, hash, filename, sourceMap)
+    }
 
     try {
       instrumented = instrumenter.instrumentSync(code, filename)
+
+      var lastSourceMap = instrumenter.lastSourceMap()
+      if (lastSourceMap) {
+        if (sourceMap) {
+          lastSourceMap = mergeSourceMap(
+                sourceMap.toObject(),
+                lastSourceMap)
+        }
+
+        instrumented += '\n' + convertSourceMap.fromObject(lastSourceMap).toComment()
+      }
     } catch (e) {
       // don't fail external tests due to instrumentation bugs.
-      console.warn('failed to instrument', filename, 'with error:', e.message)
+      console.warn('failed to instrument', filename, 'with error:', e.stack)
       instrumented = code
     }
 
@@ -269,8 +288,7 @@ NYC.prototype._transformFactory = function (cacheDir) {
   }
 }
 
-NYC.prototype._handleSourceMap = function (cacheDir, code, hash, filename) {
-  var sourceMap = convertSourceMap.fromSource(code) || convertSourceMap.fromMapFileSource(code, path.dirname(filename))
+NYC.prototype._handleSourceMap = function (cacheDir, code, hash, filename, sourceMap) {
   if (sourceMap) {
     if (hash) {
       var mapPath = path.join(cacheDir, hash + '.map')

lib/instrumenters/istanbul.js

@@ -1,12 +1,13 @@
-function InstrumenterIstanbul (cwd) {
+function InstrumenterIstanbul (cwd, options) {
   var istanbul = InstrumenterIstanbul.istanbul()
 
   return istanbul.createInstrumenter({
     autoWrap: true,
     coverageVariable: '__coverage__',
     embedSource: true,
     noCompact: false,
-    preserveComments: true
+    preserveComments: true,
+    produceSourceMap: options.produceSourceMap
   })
 }
 

package.json

@@ -88,6 +88,7 @@
     "istanbul-lib-source-maps": "^1.0.1",
     "istanbul-reports": "^1.0.0-alpha.8",
     "md5-hex": "^1.2.0",
+    "merge-source-map": "^1.0.2",
     "micromatch": "^2.3.11",
     "mkdirp": "^0.5.0",
     "pkg-up": "^1.0.0",
@@ -112,8 +113,8 @@
     "requirejs": "^2.3.0",
     "sanitize-filename": "^1.5.3",
     "sinon": "^1.15.3",
-    "source-map-support": "^0.4.2",
     "split-lines": "^1.0.0",
+    "source-map-support": "^0.4.6",
     "standard": "^8.0.0",
     "standard-version": "^2.4.0",
     "tap": "^7.0.0",

test/fixtures/stack-trace.js

@@ -0,0 +1,16 @@
+'use strict';
+
+function blah() {
+  throw new Error('Blarrh')
+}
+
+var stack;
+try {
+  blah();
+} catch(err) {
+  stack = err.stack;
+}
+
+module.exports = function() {
+  return stack;
+}

test/src/nyc-test.js

@@ -1,6 +1,6 @@
 /* global describe, it */
 
-require('source-map-support').install()
+require('source-map-support').install({hookRequire: true})
 var _ = require('lodash')
 var ap = require('any-path')
 var configUtil = require('../../lib/config-util')
@@ -202,6 +202,26 @@ describe('nyc', function () {
       })
     })
 
+    describe('produce source map', function () {
+      it('handles stack traces', function () {
+        var nyc = new NYC(configUtil.loadConfig())
+        nyc.reset()
+        nyc.wrap()
+
+        var check = require('../fixtures/stack-trace')
+        check().should.match(/stack-trace.js:4:/)
+      })
+
+      it('does not handle stack traces when disabled', function () {
+        var nyc = new NYC(configUtil.loadConfig(['--source-map=false']))
+        nyc.reset()
+        nyc.wrap()
+
+        var check = require('../fixtures/stack-trace')
+        check().should.match(/stack-trace.js:1:/)
+      })
+    })
+
     describe('compile handlers for custom extensions are assigned', function () {
       it('assigns a function to custom extensions', function () {
         var nyc = new NYC(configUtil.loadConfig([],