Fix GetBSON() method usage

[bozaro]

Original issue

You can't use type with custom GetBSON() method mixed with structure field type and structure field reference type.

For example, you can't create custom GetBSON() for Bar type:

struct Foo {
	a  Bar
	b *Bar
}

Type implementation (func (t Bar) GetBSON() ) would crash on Foo.b = nil value encoding.

Reference implementation (func (t *Bar) GetBSON() ) would not call on Foo.a value encoding.

After this change

For type implementation func (t Bar) GetBSON() would not call on Foo.b = nil value encoding.
In this case nil value would be seariazied as nil BSON value.

For reference implementation func (t *Bar) GetBSON() would call even on Foo.a value encoding.

[domodwyer]

Hey @bozaro,

Thanks for this - I agree it's a problem but I'd like to take a look at the performance/contention of this before a merge. I'll get back to you!

Dom

[domodwyer]

Hey @bozaro

I went to pull this into a local branch for testing and noticed you had a version under the performance branch using a sync.Map - looks like a good idea! Is this a work in progress? What sort of performance difference have you seen? Anything we can do to help?

Dom

[bozaro]

b1b61ed - I try to use sync.Map and got performance degradation.
50f206a - Faster key for type caching improve performance. But I'm not sure about this hack safety.

[tadukurow]

if style != getterUnknown {
return style
}

early returns save some nesting.

[bozaro]

Fixed

[domodwyer]

Hey @bozaro

We've run some tests in our staging environment and all seems well performance wise!

There's a few tests failing though:

./bson_test.go:398: undefined: bson.SetZero
./bson_test.go:417: undefined: bson.SetZero

These were changed by #44 to be ErrSetZero to keep with best practises - would you mind pushing an update and we'll get this merged?

Thanks :)

Dom

[bozaro]

@domodwyer
Rebased to development branch.