Adding tests and showing unexplained panic

[cdennison]

I've been testing getters/setters and getting a panic. I'm specifically trying to test this line (test is expected to fail):
https://github.com/casbin/casbin/blob/master/enforcer.go#L93

You can see the issue by running this code. What's strange is that when I look at the expression.Evaluate() - the parameters being passed are the same:
https://github.com/casbin/casbin/blob/master/enforcer.go#L322

fmt.Printf("%v\n",parameters)
result, err := expression.Evaluate(parameters)
//map[p_act:GET r_sub:alice r_obj:/alice_data/resource1 p_sub:alice r_act:GET p_obj:/alice_data/*]

go test -test.v -test.run ^TestInitEmpty$
=== RUN   TestInitEmpty
2017/12/08 16:07:43 [Policy:]
2017/12/08 16:07:43 [p :  sub, obj, act :  [[alice /alice_data/* GET] [alice /alice_data/resource1 POST] [bob /alice_data/resource2 GET] [bob /bob_data/* POST] [cathy /cathy_data (GET)|(POST)]]]
map[r_sub:alice p_sub:alice r_obj:/alice_data/resource1 r_act:GET p_obj:/alice_data/* p_act:GET]
--- FAIL: TestInitEmpty (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x114c2ef]

goroutine 5 [running]:
testing.tRunner.func1(0xc4200aa0f0)
	/usr/local/Cellar/go/1.9.2/libexec/src/testing/testing.go:711 +0x2d2
panic(0x11a3720, 0x12cae00)
	/usr/local/Cellar/go/1.9.2/libexec/src/runtime/panic.go:491 +0x283
github.com/casbin/casbin.(*Enforcer).Enforce(0xc42007e190, 0xc420055ea8, 0x3, 0x3, 0xc420055ea0)
	/Users/dennch3/go/thingspace/go/src/github.com/casbin/casbin/enforcer.go:324 +0x71f
github.com/casbin/casbin.testEnforce(0xc4200aa0f0, 0xc42007e190, 0x11d2358, 0x5, 0x1191b60, 0x11f33c0, 0x11d1fe2, 0x3, 0x1073401)
	/Users/dennch3/go/thingspace/go/src/github.com/casbin/casbin/model_test.go:26 +0x144
github.com/casbin/casbin.TestInitEmpty(0xc4200aa0f0)
	/Users/dennch3/go/thingspace/go/src/github.com/casbin/casbin/enforcer_test.go:402 +0x267
testing.tRunner(0xc4200aa0f0, 0x11dd478)
	/usr/local/Cellar/go/1.9.2/libexec/src/testing/testing.go:746 +0xd0
created by testing.(*T).Run
	/usr/local/Cellar/go/1.9.2/libexec/src/testing/testing.go:789 +0x2de
exit status 2
FAIL	github.com/casbin/casbin	0.833s

[hsluoyz]

Hi. Thanks for pointing this out. I found this is a bug in Enforcer.SetModel(). The matcher functions such as keyMatch and regexMatch are not loaded when you initialize the model via Enforcer.SetModel(). I have fixed it in: 9bb178c

[hsluoyz]

Suppose this can be closed now.

[cdennison]

@hsluoyz - sorry for not getting back to you sooner - do you want to add the test cases from my PR? I can resubmit to show that they are now passing.

[hsluoyz]

I think you can resubmit these tests in a new PR :)