tree eba61ba92008ad05eba8e890ba31badf6cacbaab
parent 838f1f50f9e8dc425c25fe2519ae4b926ac2fd32
author Joe Tsai <joetsai@digital-static.net> 1558032352 -0700
committer Joe Tsai <joetsai@digital-static.net> 1558037865 +0000

internal/impl: add scaffolding for lazy extension support

Once the ExtensionFieldV1.Value field is unexported, it forces all
read operations to go through GetValue, which can perform some form
of lazy retrieval.

The SetEagerValue method is equivalent to setting the Value directly.
The SetLazyValue method permits setting a lazy equivalent of the Value
by simply storing a function closure returning the value.

Change-Id: I410f74924f0957f5eadc82eea3669ca335a02701
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/177619
Reviewed-by: Damien Neil <dneil@google.com>