api/unitassigner: data race

[Dave Cheney]

lucky(~/src/github.com/juju/juju/api/unitassigner) % go test -race .
==================
WARNING: DATA RACE
Write by goroutine 16:
  github.com/juju/juju/api/unitassigner.(*fakeWatchCaller).APICall()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/unitassigner_test.go:108 +0x51
  github.com/juju/juju/api/watcher.makeWatcherAPICaller.func1()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:49 +0x17b
  github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop.func2()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:95 +0x15c

Previous read by goroutine 12:
  runtime.convT2E()
      /home/dfc/go/src/runtime/iface.go:128 +0x0
  github.com/juju/juju/api/unitassigner.testsuite.TestWatchUnitAssignment()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/unitassigner_test.go:66 +0x262
  github.com/juju/juju/api/unitassigner.(*testsuite).TestWatchUnitAssignment()
      <autogenerated>:20 +0xbb
  runtime.call32()
      /home/dfc/go/src/runtime/asm_amd64.s:471 +0x3d
  reflect.Value.Call()
      /home/dfc/go/src/reflect/value.go:303 +0xcd
  gopkg.in/check%2ev1.(*suiteRunner).forkTest.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:772 +0x5d1
  gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:666 +0x80

Goroutine 16 (running) created at:
  github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:118 +0x118

Goroutine 12 (finished) created at:
  gopkg.in/check%2ev1.(*suiteRunner).forkCall()
      /home/dfc/src/gopkg.in/check.v1/check.go:667 +0x48b
  gopkg.in/check%2ev1.(*suiteRunner).forkTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:804 +0x126
  gopkg.in/check%2ev1.(*suiteRunner).runTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:809 +0x38
  gopkg.in/check%2ev1.(*suiteRunner).run()
      /home/dfc/src/gopkg.in/check.v1/check.go:615 +0x481
  gopkg.in/check%2ev1.Run()
      /home/dfc/src/gopkg.in/check.v1/run.go:92 +0x50
  gopkg.in/check%2ev1.RunAll()
      /home/dfc/src/gopkg.in/check.v1/run.go:84 +0x138
  gopkg.in/check%2ev1.TestingT()
      /home/dfc/src/gopkg.in/check.v1/run.go:72 +0x4af
  github.com/juju/juju/api/unitassigner.TestPackage()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/package_test.go:13 +0x2e
  testing.tRunner()
      /home/dfc/go/src/testing/testing.go:456 +0xdc
==================
==================
WARNING: DATA RACE
Write by goroutine 16:
  github.com/juju/juju/api/unitassigner.(*fakeWatchCaller).APICall()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/unitassigner_test.go:109 +0x8e
  github.com/juju/juju/api/watcher.makeWatcherAPICaller.func1()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:49 +0x17b
  github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop.func2()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:95 +0x15c

Previous read by goroutine 12:
  github.com/juju/juju/api/unitassigner.testsuite.TestWatchUnitAssignment()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/unitassigner_test.go:67 +0x2dd
  github.com/juju/juju/api/unitassigner.(*testsuite).TestWatchUnitAssignment()
      <autogenerated>:20 +0xbb
  runtime.call32()
      /home/dfc/go/src/runtime/asm_amd64.s:471 +0x3d
  reflect.Value.Call()
      /home/dfc/go/src/reflect/value.go:303 +0xcd
  gopkg.in/check%2ev1.(*suiteRunner).forkTest.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:772 +0x5d1
  gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1()
      /home/dfc/src/gopkg.in/check.v1/check.go:666 +0x80

Goroutine 16 (running) created at:
  github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop()
      /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:118 +0x118

Goroutine 12 (finished) created at:
  gopkg.in/check%2ev1.(*suiteRunner).forkCall()
      /home/dfc/src/gopkg.in/check.v1/check.go:667 +0x48b
  gopkg.in/check%2ev1.(*suiteRunner).forkTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:804 +0x126
  gopkg.in/check%2ev1.(*suiteRunner).runTest()
      /home/dfc/src/gopkg.in/check.v1/check.go:809 +0x38
  gopkg.in/check%2ev1.(*suiteRunner).run()
      /home/dfc/src/gopkg.in/check.v1/check.go:615 +0x481
  gopkg.in/check%2ev1.Run()
      /home/dfc/src/gopkg.in/check.v1/run.go:92 +0x50
  gopkg.in/check%2ev1.RunAll()
      /home/dfc/src/gopkg.in/check.v1/run.go:84 +0x138
  gopkg.in/check%2ev1.TestingT()
      /home/dfc/src/gopkg.in/check.v1/run.go:72 +0x4af
  github.com/juju/juju/api/unitassigner.TestPackage()
      /home/dfc/src/github.com/juju/juju/api/unitassigner/package_test.go:13 +0x2e
  testing.tRunner()
      /home/dfc/go/src/testing/testing.go:456 +0xdc
==================
OK: 3 passed
PASS
Found 2 data race(s)
FAIL github.com/juju/juju/api/unitassigner 1.092s

[Dave Cheney (dave-cheney)]

Bug was introduced in https://github.com/juju/juju/commit/e8934a0b, along with

# github.com/juju/juju/api/unitassigner
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x4890ef]

goroutine 26 [running]:
github.com/juju/juju/api/unitassigner.(*fakeWatchCaller).APICall(0xc8201fa900, 0xab5a30, 0xe, 0x1, 0x0, 0x0, 0xaa5e88, 0x4, 0x0, 0x0, ...)
        /home/dfc/src/github.com/juju/juju/api/unitassigner/unitassigner_test.go:113 +0x1af
github.com/juju/juju/api/watcher.makeWatcherAPICaller.func1(0xaa5e88, 0x4, 0x8b7f80, 0xc8201fd4f0, 0x0, 0x0)
        /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:49 +0x16b
github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop.func2(0xc8201fd4e0, 0xc82022da40)
        /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:95 +0xec
created by github.com/juju/juju/api/watcher.(*commonWatcher).commonLoop
        /home/dfc/src/github.com/juju/juju/api/watcher/watcher.go:118 +0xe1
FATAL: command "test" failed: exit status 2