The improved err scanner loop in meta causes these to race. There's no
need to write back to the same commands struct, so just use a new
instance in each iteration.
Previously the APIs for state persistence and management had some problematic cases where we depended on hidden mutations of the state structure as side-effects of otherwise-innocent-looking operations, which was a frequent cause of accidental regressions due to faulty assumptions.
This new model attempts to isolate certain state mutations to just within the state managers, and makes the state managers work on separated snapshots of the state rather than on the "live" object to reduce the risk of race conditions.
This command serves as an alternative to the human-oriented list of workspaces for scripting use-cases where it's useful to know the _current_ workspace name.
Previously we relied on a constellation of coincidences for everything to
work out correctly with state serials. In particular, callers needed to
be very careful about mutating states (or not) because many different bits
of code shared pointers to the same objects.
Here we move to a model where all of the state managers always use
distinct instances of state, copied when WriteState is called. This means
that they are truly a snapshot of the state as it was at that call, even
if the caller goes on mutating the state that was passed.
We also adjust the handling of serials so that the state managers ignore
any serials in incoming states and instead just treat each Persist as
the next version after what was most recently Refreshed.
(An exception exists for when nothing has been refreshed, e.g. because
we are writing a state to a location for the first time. In that case
we _do_ trust the caller, since the given state is either a new state
or it's a copy of something we're migrating from elsewhere with its
state and lineage intact.)
The intent here is to allow the rest of Terraform to not worry about
serials and state identity, and instead just treat the state as a mutable
structure. We'll just snapshot it occasionally, when WriteState is called,
and deal with serials _only_ at persist time.
This is intended as a more robust version of #15423, which was a quick
hotfix to an issue that resulted from our previous slopping handling
of state serials but arguably makes the problem worse by depending on
an additional coincidental behavior of the local backend's apply
implementation.
We're shifting terminology from "environment" to "workspace". This takes
care of some of the main internal API surface that was using the old
terminology, though is not intended to be entirely comprehensive and is
mainly just to minimize the amount of confusion for maintainers as we
continue moving towards eliminating the old terminology.
Feedback after 0.9 was that the term "environment" was confusing due to
it colliding with several other concepts, such as OS environment
variables, a non-aligned Terraform Enterprise concept, and differing ideas
of "environment" within various organizations.
This new term "workspace" is intended to ease some of that confusion. This
term is not used anywhere else in Terraform today, and we expect it to not
be used in a manner that would be confusing within user organizations.
This begins a deprecation cycle for the "terraform env" family of commands,
instead moving to an equivalent set of "terraform workspace" commands.
There are some remaining references to the old "environment" concept in
the code, which will be cleaned up in a separate change. This change is
instead focused on text visible in the UI and wording within code comments
for the benefit of human maintainers of the code.
