This change fixes up a few things so that updates correctly deal
with output properties. This involves a few things:
1) All outputs stored on the pre snapshot need to get propagated
to the post snapshot during planning at various points. This
ensures that the diffing logic doesn't need to be special cased
everywhere, including both the Lumi and the provider sides.
2) Names are changed to "input" properties (using a new `lumi` tag
option, `in`). These are properties that providers are expected
to know nothing about, which we must treat with care during diffs.
3) We read back properties, via Get, after doing an Update just like
we do after performing a Create. This ensures that if an update
has a cascading impact on other properties, it will be detected.
4) Inspecting a change, prior to updating, must be done using the
computed property set instead of the real one. This is to avoid
mutating the resource objects ahead of actually applying a plan,
which would be wrong and misleading.
This change skips printing output<T> properties as we perform a
deployment, instead showing the real values inline after the resource
has been created. (output<T> is still shown during planning, of course.)
The change to flow logging to plugins is nice, however, it can be
annoying because all writes to stderr are interepreted on the Lumi
side as errors. After this change, we will only flow if
--logflow is passed, e.g. as in
$ lumi --logtostderr --logflow -v=9 deploy ...
This change prepares for integrating more planning and deployment logic
closer to the runtime itself. For historical reasons, we ended up with these
in the env.go file which really has nothing to do with deployments anymore.
This change introduces the notion of a computed versus an output
property on resources. Technically, output is a subset of computed,
however it is a special kind that we want to treat differently during
the evaluation of a deployment plan. Specifically:
* An output property is any property that is populated by the resource
provider, not code running in the Lumi type system. Because these
values aren't available during planning -- since we have not yet
performed the deployment operations -- they will be latent values in
our runtime and generally missing at the time of a plan. This is no
problem and we just want to avoid marshaling them in inopportune places.
* A computed property, on the other hand, is a different beast altogehter.
Although true one of these is missing a value -- by virtue of the fact
that they too are latent values, bottoming out in some manner on an
output property -- they will appear in serializable input positions.
Not only must we treat them differently during the RPC handshake and
in the resource providers, but we also want to guarantee they are gone
by the time we perform any CRUD operations on a resource. They are
purely a planning-time-only construct.
This change includes approximately 1/3rd of the change necessary
to support output properties, as per pulumi/lumi#90.
In short, the runtime now has a new hidden type, Latent<T>, which
represents a "speculative" value, whose eventual type will be T,
that we can use during evaluation in various ways. Namely,
operations against Latent<T>s generally produce new Latent<U>s.
During planning, any Latent<T>s that end up in resource properties
are transformed into "unknown" property values. An unknown property
value is legal only during planning-time activities, such as Check,
Name, and InspectChange. As a result, those RPC interfaces have
been updated to include lookaside maps indicating which properties
have unknown values. My intent is to add some helper functions to
make dealing with this circumstance more correct-by-construction.
For now, using an unresolved Latent<T> in a conditional will lead
to an error. See pulumi/lumi#67. Speculating beyond these -- by
supporting iterative planning and application -- is something we
want to support eventually, but it makes sense to do that as an
additive change beyond this initial support. That is a missing 1/3.
Finally, the other missing 1/3rd which will happen much sooner
than the rest is restructuing plan application so that it will
correctly observe resolution of Latent<T> values. Right now, the
evaluation happens in one single pass, prior to the application, and
so Latent<T>s never actually get witnessed in a resolved state.
