This was a mistake while adapting this code from the old state.LocalState.
Since the lock is held on the output file (s.path) the metadata should
live adjacent to that rather than being built from the read path
(s.readPath) that is used only as the initial snapshot on first
instantiation.
This also includes more logging, continuing the trend of other recent
commits in these files. The local state behavior is sufficiently complex
that these trace logs are a great help in debugging issues such as this
one with the wrong files being used or actions being taken in the wrong
order.
This idea of a "state manager" was previously modelled via the
confusingly-named state.State interface, which we've been calling a "state
manager" only in some local variable names in situations where there were
also *terraform.State variables.
As part of reworking our state models to make room for the new type
system, we also need to change what was previously the state.StateReader
interface. Since we've found the previous organization confusing anyway,
here we just copy all of those interfaces over into statemgr where we can
make the relationship to states.State hopefully a little clearer.
This is not yet a complete move of the functionality from "state", since
we're not yet ready to break existing callers. In a future commit we'll
turn the interfaces in the old "state" package into aliases of the
interfaces in this package, and update all the implementers of what will
by then be statemgr.Reader to use *states.State instead of
*terraform.State.
This also includes an adaptation of what was previously state.LocalState
into statemgr.FileSystem, using the new state serialization functionality
from package statefile instead of the old terraform.ReadState and
terraform.WriteState.
Martin Atkins