Compare options are not optional

[anyasabo]

Trying to compare identical empty objects or other simple objects results in a panic if no options are provided. The name is a little misleading since options imply (to me at least) that they are not required.

For instance:
diff, _ := jsondiff.Compare([]byte({}), []byte({}), nil)

Adding opts := DefaultConsoleOptions() and passing it in (as in the unit tests) prevent it from panicking. I didn't get a chance to see what it is expecting just yet.

Output:

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=0x5b272a]

goroutine 6 [running]:
testing.tRunner.func1.1(0x5d7ce0, 0x760ed0)
	/usr/local/go-faketime/src/testing/testing.go:1076 +0x30d
testing.tRunner.func1(0xc000001b00)
	/usr/local/go-faketime/src/testing/testing.go:1079 +0x41a
panic(0x5d7ce0, 0x760ed0)
	/usr/local/go-faketime/src/runtime/panic.go:969 +0x175
github.com/nsf/jsondiff.(*context).printDiff(0xc000045ec0, 0x5d6c60, 0xc000073260, 0x5d6c60, 0xc000073290)
	/tmp/gopath249660858/pkg/mod/github.com/nsf/jsondiff@v0.0.0-20200515183724-f29ed568f4ce/jsondiff.go:329 +0x4ea
github.com/nsf/jsondiff.Compare(0xc00002c9b0, 0x8, 0x8, 0xc00002c9b8, 0x8, 0x8, 0x0, 0x4b5a86, 0x4af9f070, 0x0)
	/tmp/gopath249660858/pkg/mod/github.com/nsf/jsondiff@v0.0.0-20200515183724-f29ed568f4ce/jsondiff.go:414 +0x296
main.Test_jsondiffnoopts(0xc000001b00)
	/tmp/sandbox175228423/prog.go:11 +0xaa
testing.tRunner(0xc000001b00, 0x61efb8)
	/usr/local/go-faketime/src/testing/testing.go:1127 +0xef
created by testing.(*T).Run
	/usr/local/go-faketime/src/testing/testing.go:1178 +0x386

Simple examples here: https://play.golang.org/p/vSdHmaOY3zw

On a different note, thank you for sharing this repo. I have a project where we are not using it for debugging, but it is useful for finding superset matches in arbitrary json bodies.

[pjebs]

Yes. You can pass in any option and just ignore the second return value of Compare function.

In terms of API design, the different built-in options should return pointers instead of concrete types.

[nsf]

Sorry for a late response. I guess calling "options" is not the best idea. As it's not optional. I will think about renaming it to "Arguments" or something like that before releasing 1.0.

Sadly I don't see a way to actually make it optional as there is no generic format. Most formats are specific to their environment. Be it JSON, linux terminal or HTML.

Perhaps I should call it "Formatt". E.g. "DefaultConsoleFormat()". But then it contains options also right now. Naming is hard.