get istanbul and sandboxed-module to party

istanbul-sandbox.coffee

SandboxedModule = require('sandboxed-module')

global.requireSubject = (path, requires) ->
  SandboxedModule.require("./../../#{path}",  {requires})

_ = require('underscore')
coverageVariable = _(global).chain().keys().find((k) -> k.indexOf("$$cov_") == 0).value()

if coverageVariable?
  fs = require("fs")

  SandboxedModule::_getCompileInfo = ->
    localVariables = []
    localValues = []
    for localVariable of @locals
      localVariables.push localVariable
      localValues.push @locals[localVariable]
    sourceToWrap = instrument(fs.readFileSync(@filename, "utf8"), @filename)

    if @filename.search(".coffee$") != -1
      try
        coffeeScript = require("coffee-script")
        sourceToWrap = coffeeScript.compile(sourceToWrap)

    source = "global = GLOBAL = root = (function() { return this; })();" + "(function(" + localVariables.join(", ") + ") { " + sourceToWrap + "\n" + "return global;\n" + "});"
    source: source
    parameters: localValues

  snagInstrumentTransformerFromIstanbul = ->
    Instrumenter = require('istanbul').Instrumenter
    instrumenter = new Instrumenter({coverageVariable})
    instrumenter.instrumentSync.bind(instrumenter)

  instrument = snagInstrumentTransformerFromIstanbul()

Turns out this actually works. Basically we monkey-patch sandboxed-module such that what it wraps is actually instrumented JavaScript. (We get that instrumented JavaScript by figuring out what the global coverage variable is in order to generate an istanbul instrumentation transformer function)

In this case, this is just stuck in a spec helper in my test suite. The global.requireSubject() is just a little convenience we use for requiring the thing under test, it's not entirely pertinent.

cool.

I had a similar issue when I tried to get something I build with component to build with browserify, I ended up making a grunt plugin that would use espirma to rename all the instances of require in one of them.