feat: read coverage header when using "noop" instrumenter (#420)

index.js

@@ -84,6 +84,8 @@ function NYC (config) {
 
   this.processInfo = new ProcessInfo(config && config._processInfo)
   this.rootId = this.processInfo.root || this.generateUniqueID()
+  this.instrument = config.instrument
+  this.all = config.all
 }
 
 NYC.prototype._createTransform = function (ext) {
@@ -166,6 +168,9 @@ NYC.prototype.addAllFiles = function () {
     _this.addFile(filename)
     var coverage = coverageFinder()
     var lastCoverage = _this.instrumenter().lastFileCoverage()
+    if (lastCoverage) {
+      filename = lastCoverage.path
+    }
     if (lastCoverage && _this.exclude.shouldInstrument(filename)) {
       coverage[filename] = lastCoverage
     }
@@ -233,7 +238,7 @@ NYC.prototype.walkAllFiles = function (dir, visitor) {
 }
 
 NYC.prototype._maybeInstrumentSource = function (code, filename, relFile) {
-  var instrument = this.exclude.shouldInstrument(filename, relFile)
+  var instrument = (!this.instrument && this.all) || this.exclude.shouldInstrument(filename, relFile)
   if (!instrument) {
     return null
   }

lib/instrumenters/noop.js

@@ -1,10 +1,19 @@
+var FileCoverage = require('istanbul-lib-coverage').classes.FileCoverage
+var readInitialCoverage = require('istanbul-lib-instrument').readInitialCoverage
+
 function NOOP () {
   return {
     instrumentSync: function (code) {
+      var extracted = readInitialCoverage(code)
+      if (extracted) {
+        this.fileCoverage = new FileCoverage(extracted.coverageData)
+      } else {
+        this.fileCoverage = null
+      }
       return code
     },
     lastFileCoverage: function () {
-      return null
+      return this.fileCoverage
     }
   }
 }