In study of existing providers we've found a pattern we werent previously
accounting for of using a nested block type to represent a group of
arguments that relate to a particular feature that is always enabled but
where it improves configuration readability to group all of its settings
together in a nested block.
The existing NestingSingle was not a good fit for this because it is
designed under the assumption that the presence or absence of the block
has some significance in enabling or disabling the relevant feature, and
so for these always-active cases we'd generate a misleading plan where
the settings for the feature appear totally absent, rather than showing
the default values that will be selected.
NestingGroup is, therefore, a slight variation of NestingSingle where
presence vs. absence of the block is not distinguishable (it's never null)
and instead its contents are treated as unset when the block is absent.
This then in turn causes any default values associated with the nested
arguments to be honored and displayed in the plan whenever the block is
not explicitly configured.
The current SDK cannot activate this mode, but that's okay because its
"legacy type system" opt-out flag allows it to force a block to be
processed in this way anyway. We're adding this now so that we can
introduce the feature in a future SDK without causing a breaking change
to the protocol, since the set of possible block nesting modes is not
extensible.
* command/show: adding functions to aid refactoring
The planfile -> statefile -> state logic path was getting hard to follow
with blurry human eyes. The getPlan... and getState... functions were
added to help streamline the logic flow. Continued refactoring may follow.
* command/show: use ctx.Config() instead of a config snapshot
As originally written, the jsonconfig marshaller was getting an error
when loading configs that included one or more modules. It's not clear
if that was an error in the function call or in the configloader itself,
but as a simpler solution existed I did not dig too far.
* command/jsonplan: implement jsonplan.Marshal
Split the `config` portion into a discrete package to aid in naming
sanity (so we could have for example jsonconfig.Resource instead of
jsonplan.ConfigResource) and to enable marshaling the config on it's
own.
Martin Atkins