This adds back Computed<T> as a short-hand for Promise<T | undefined>.
Subtly, all resource properties need to permit undefined flowing through
during planning Rather than forcing the long-hand version, which is easy
to forget, we'll keep the convention of preferring Computed<T>. It's
just a typedef and the runtime type is just a Promise.
As part of pulumi/pulumi-fabric#331, we've been exploring just using
undefined to indicate that a property value is absent during planning.
We also considered blocking the message loop to simplify the overall
programming model, so that all asynchrony is hidden.
It turns out ThereBeDragons 🐲 anytime you try to block the
message loop. So, we aren't quite sure about that bit.
But the part we are convicted about is that this Computed/Property
model is far too complex. Furthermore, it's very close to promises, and
yet frustratingly so far away. Indeed, the original thinking in
pulumi/pulumi-fabric#271 was simply to use promises, but we wanted to
encourage dataflow styles, rather than control flow. But we muddied up
our thinking by worrying about awaiting a promise that would never resolve.
It turns out we can achieve a middle ground: resolve planning promises to
undefined, so that they don't lead to hangs, but still use promises so
that asynchrony is explicit in the system. This also avoids blocking the
message loop. Who knows, this may actually be a fine final destination.
This change adds an optiona dependsOn parameter to Resource constructors,
to "force" a fake dependency between resources. We have an extremely strong
desire to resort to using this only in unusual cases -- and instead rely
on the natural dependency DAG based on properties -- but experience in other
resource provisioning frameworks tells us that we're likely to need this in
the general case. Indeed, we've already encountered the need in AWS's
API Gateway resources... and I suspect we'll run into more especially as we
tackle non-serverless resources like EC2 Instances, where "ambient"
dependencies are far more commonplace.
This also makes parallelism the default mode of operation, and we have a
new --serialize flag that can be used to suppress this default behavior.
Full disclosure: I expect this to become more Make-like, i.e. -j 8, where
you can specify the precise width of parallelism, when we tackle
pulumi/pulumi-fabric#106. I also think there's a good chance we will flip
the default, so that serial execution is the default, so that developers
who don't benefit from the parallelism don't need to worry about dependsOn
in awkward ways. This tends to be the way most tools (like Make) operate.
This fixespulumi/pulumi-fabric#335.
As I started rolling this out, I realized that end user code actually
has to use this type sometimes. And that the current names are inconsistent,
after eschewing Property<T> in favor of Computed<T>. The new names read better.
This change makes a few simplifications to how properties are exposed in
the system, mostly in the name of usability, but also to feel a bit more
like "idiomatic JavaScript". Namely:
* Rename `then` to `mapValue`. This hopefully helps to suggest that this
is meant for a dataflow style of programming.
* Move Property<T> into the runtime module, and remove PropertyState<T>,
collapsing back down to a single type. This also eliminates some of the
messy internal runtime casting, accessing of internal members, etc.
* Export a Computed<T> interface from the root of the module. This is
the entirety of the public-facing surface area for properties, and
exposes that single `mapValue` member function. The internal runtime
logic understands how to handle Property<T>s specifically in addition
to Computed<T>s more generally (in case someone writes their own).
The organization of packages underneath lib/ breaks the easy consumption
of submodules, a la
import {FileAsset} from "@pulumi/pulumi-fabric/asset";
We will go back to having everything hanging off the module root directory.
