fix: race condition between the Karma shutdown and coverage writing

The creation of parent directories is asynchronous process, which was not properly awaited, which resulted in the coverage reports not being written to the disk sometimes as Karma process has exited before the reporter completed the writing of the coverage report.

Also update the test case to use async implementation of the corresponding stub to prevent regressions in the future. Remove manual calls for `done` parameter in tests as it is handled by the stub now.

Fixes #434

lib/reporter.js

@@ -11,6 +11,7 @@
 // ------------
 
 var path = require('path')
+const { promisify } = require('util')
 var istanbulLibCoverage = require('istanbul-lib-coverage')
 var istanbulLibReport = require('istanbul-lib-report')
 var minimatch = require('minimatch')
@@ -264,10 +265,12 @@ var CoverageReporter = function (rootConfig, helper, logger, emitter) {
       return
     }
 
-    helper.mkdirIfNotExists(outputPath, function () {
-      log.debug('Writing coverage to %s', outputPath)
-      report.execute(context)
-    })
+    const mkdirIfNotExists = promisify(helper.mkdirIfNotExists)
+    await mkdirIfNotExists(outputPath)
+
+    log.debug('Writing coverage to %s', outputPath)
+    report.execute(context)
+
     return results
   }
 

test/reporter.spec.js

@@ -27,7 +27,10 @@ describe('reporter', () => {
   const mockHelper = {
     isDefined: (v) => helper.isDefined(v),
     merge: (...arg) => helper.merge(...arg),
-    mkdirIfNotExists: mkdirIfNotExistsStub,
+    mkdirIfNotExists: (dir, done) => {
+      mkdirIfNotExistsStub(dir, done)
+      setTimeout(done, 0)
+    },
     normalizeWinPath: (path) => helper.normalizeWinPath(path)
   }
 
@@ -166,7 +169,6 @@ describe('reporter', () => {
       const dir = rootConfig.coverageReporter.dir
       expect(mkdirIfNotExistsStub.getCall(0).args[0]).to.deep.equal(resolve('/base', dir, fakeChrome.name))
       expect(mkdirIfNotExistsStub.getCall(1).args[0]).to.deep.equal(resolve('/base', dir, fakeOpera.name))
-      mkdirIfNotExistsStub.getCall(0).args[1]()
       expect(reportCreateStub).to.have.been.called
       expect(mockPackageSummary.execute).to.have.been.called
       const createArgs = reportCreateStub.getCall(0).args
@@ -192,7 +194,6 @@ describe('reporter', () => {
       const subdir = customConfig.coverageReporter.subdir
       expect(mkdirIfNotExistsStub.getCall(0).args[0]).to.deep.equal(resolve('/base', dir, subdir))
       expect(mkdirIfNotExistsStub.getCall(1).args[0]).to.deep.equal(resolve('/base', dir, subdir))
-      mkdirIfNotExistsStub.getCall(0).args[1]()
       expect(reportCreateStub).to.have.been.called
       expect(mockPackageSummary.execute).to.have.been.called
     })
@@ -213,7 +214,6 @@ describe('reporter', () => {
       const dir = customConfig.coverageReporter.dir
       expect(mkdirIfNotExistsStub.getCall(0).args[0]).to.deep.equal(resolve('/base', dir, 'chrome'))
       expect(mkdirIfNotExistsStub.getCall(1).args[0]).to.deep.equal(resolve('/base', dir, 'opera'))
-      mkdirIfNotExistsStub.getCall(0).args[1]()
       expect(reportCreateStub).to.have.been.called
       expect(mockPackageSummary.execute).to.have.been.called
     })
@@ -246,7 +246,6 @@ describe('reporter', () => {
       expect(mkdirIfNotExistsStub.getCall(1).args[0]).to.deep.equal(resolve('/base', 'reporter1', 'opera'))
       expect(mkdirIfNotExistsStub.getCall(2).args[0]).to.deep.equal(resolve('/base', 'reporter2', 'CHROME'))
       expect(mkdirIfNotExistsStub.getCall(3).args[0]).to.deep.equal(resolve('/base', 'reporter2', 'OPERA'))
-      mkdirIfNotExistsStub.getCall(0).args[1]()
       expect(reportCreateStub).to.have.been.called
       expect(mockPackageSummary.execute).to.have.been.called
     })
@@ -277,7 +276,6 @@ describe('reporter', () => {
       expect(mkdirIfNotExistsStub.getCall(1).args[0]).to.deep.equal(resolve('/base', 'reporter1', 'defaultsubdir'))
       expect(mkdirIfNotExistsStub.getCall(2).args[0]).to.deep.equal(resolve('/base', 'defaultdir', 'CHROME'))
       expect(mkdirIfNotExistsStub.getCall(3).args[0]).to.deep.equal(resolve('/base', 'defaultdir', 'OPERA'))
-      mkdirIfNotExistsStub.getCall(0).args[1]()
       expect(reportCreateStub).to.have.been.called
       expect(mockPackageSummary.execute).to.have.been.called
     })