When the user aborts input, it may end up as an unknown value, which
needs to be converted to null for PrepareConfig.
Allow PrepareConfig to accept null config values in order to fill in
missing defaults.
This mirrors the change made for providers, so that default values can
be inserted into the config by the backend implementation. This is only
the interface and method name changes, it does not yet add any default
values.
Terraform now handles any actual "diffing" of resource, and the existing
Diff functions are only used to shim the schema.Provider to the new
methods. Since terraform is handling what used to be the Diff, the
provider now should not modify the diff based on RequiresNew due to it
interfering with the ignore_changes handling.
The "config" package is no longer used and will be removed as part
of the 0.12 release cleanup. Since configschema is part of the
"new world" of configuration modelling, it makes more sense for
it to live as a subdirectory of the newer "configs" package.
The new config loader requires some steps to happen in a different
order, particularly in regard to knowing the schema in order to
decode the configuration.
Here we lean directly on the configschema package, rather than
on helper/schema.Backend as before, because it's generally
sufficient for our needs here and this prepares us for the
helper/schema package later moving out into its own repository
to seed a "plugin SDK".
It's alive! CustomizeDiff logic now has been inserted into the diff
process. The test_resource_with_custom_diff resource provides some basic
testing and a reference implementation.
There should now be plenty of test coverage for this feature via the
tests added for ResourceDiff, and the basic test added to the
schemaMap.Diff test, and the test resource, but more can be added to
test any specific case that comes up otherwise.
Alex Pilon