This change implements the `get` function for resources. Per pulumi/lumi#83,
this allows Lumi scripts to actually read from the target environment.
For example, we can now look up a SecurityGroup from its ARN:
let group = aws.ec2.SecurityGroup.get(
"arn:aws:ec2:us-west-2:153052954103:security-group:sg-02150d79");
The returned object is a fully functional resource object. So, we can then
link it up with an EC2 instance, for example, in the usual ways:
let instance = new aws.ec2.Instance(..., {
securityGroups: [ group ],
});
This didn't require any changes to the RPC or provider model, since we
already implement the Get function.
There are a few loose ends; two are short term:
1) URNs are not rehydrated.
2) Query is not yet implemented.
One is mid-term:
3) We probably want a URN-based lookup function. But we will likely
wait until we tackle pulumi/lumi#109 before adding this.
And one is long term (and subtle):
4) These amount to I/O and are not repeatable! A change in the target
environment may cause a script to generate a different plan
intermittently. Most likely we want to apply a different kind of
deployment "policy" for such scripts. These are inching towards the
scripting model of pulumi/lumi#121, which is an entirely different
beast than the repeatable immutable infrastructure deployments.
Finally, it is worth noting that with this, we have some of the fundamental
underpinnings required to finally tackle "inference" (pulumi/lumi#142).
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