[sdk/go] Track rehydrated components as dependencies

[justinvp]

When expanding dependencies, local component resources act as aggregations of their descendants; rather than adding the component resource itself, each child resource is added as a dependency. Remote component resources, on the other hand, are added directly to the set, as they naturally act as aggregations of their children with respect to dependencies: the construction of a remote component always waits on the construction of its children.

pulumi/sdk/go/pulumi/rpc.go

Lines 65 to 91 in 46ccb5a

	// addDependency adds a dependency on the given resource to the set of deps.
	//
	// The behavior of this method depends on whether or not the resource is a custom resource, a local component resource,
	// or a remote component resource:
	//
	// - Custom resources are added directly to the set, as they are "real" nodes in the dependency graph.
	// - Local component resources act as aggregations of their descendents. Rather than adding the component resource
	// itself, each child resource is added as a dependency.
	// - Remote component resources are added directly to the set, as they naturally act as aggregations of their children
	// with respect to dependencies: the construction of a remote component always waits on the construction of its
	// children.
	//
	// In other words, if we had:
	//
	// Comp1
	// / | \
	// Cust1 Comp2 Remote1
	// / \ \
	// Cust2 Cust3 Comp3
	// / \
	// Cust4 Cust5
	//
	// Then the transitively reachable resources of Comp1 will be [Cust1, Cust2, Cust3, Remote1].
	// It will *not* include:
	// * Cust4 because it is a child of a custom resource
	// * Comp2 because it is a non-remote component resoruce
	// * Comp3 and Cust5 because Comp3 is a child of a remote component resource

However, rehydrated components (i.e. instances of a component resource that have been recreated from a URN, typically via deserialization of a resource reference) aren't marked as a remote component and won't have any children from the SDK's perspective. And because of that, when their outputs are used, there won't be any dependencies kept for those outputs.

This change fixes rehydrated components to be marked as remote components, in the same way as "dependency resources" are marked as remote components, so that they are kept as a dependency.

This addresses cases where a component resource method is implemented in Go and the method returns results derived from the component's outputs. Inside the implementation of the provider's Call, the implementation will get a rehydrated instance of the component. Without this fix, the dependency on that component will not be kept in the returned output.

Here's a concrete example:

pulumi/tests/integration/construct_component_methods/testcomponent-go/main.go

Lines 64 to 68 in 5d3372b

	func (c *Component) GetMessage(args *ComponentGetMessageArgs) (*ComponentGetMessageResult, error) {
	return &ComponentGetMessageResult{
	Message: pulumi.Sprintf("%s %s, %s!", c.First, c.Second, args.Name),
	}, nil
	}

The above is a method implemented in a component provider. The c *Component receiver will be a rehydrated instance of the component. The method uses pulumi.Sprintf to create a result that combines some of the component's outputs. But the combined output that is returned won't have the dependency on the component kept, since the rehydrated component is a component and doesn't have any children. With the fix, the dependency will be kept and serialized as expected.

Part of #12471

[pulumi-bot]

Changelog

[uncommitted] (2023-03-24)

Bug Fixes

• [sdk/go] Track rehydrated components as dependencies
  #12494

[dixler]

I think I have a better understanding how the SDK views local components after reading this. I have some nitpicks that should help future readability from the POV of someone trying to skim this for the first time.

[justinvp]

Thanks for the feedback! I've addressed your comments.

[dixler]

Looks great to me. Thanks for updatingmodifying the comments!

[justinvp]

bors merge p=1

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