From ab5bf50fc3a185ef722e2b57db2a5eb6bc7a2226 Mon Sep 17 00:00:00 2001
From: Kristin Laemmert <mildwonkey@users.noreply.github.com>
Date: Fri, 25 Sep 2020 12:18:20 -0400
Subject: [PATCH] terrafrom: create NodeAbstractResource
 ReadResourceInstanceState function

The original EvalReadState node is used only by `NodeAbstractResource`s,
so I've created a new method on NodeAbstractResource which does the same
thing as EvalReadState. When the EvalNode refactor project is complete,
EvalReadState will be removed entirely.
---
 terraform/node_resource_abstract.go    | 42 ++++++++++++++++++++++++++
 terraform/node_resource_destroy.go     |  8 +----
 terraform/node_resource_plan_orphan.go | 11 ++-----
 3 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/terraform/node_resource_abstract.go b/terraform/node_resource_abstract.go
index f74d651f3..8aef0a9b6 100644
--- a/terraform/node_resource_abstract.go
+++ b/terraform/node_resource_abstract.go
@@ -496,6 +496,48 @@ func (n *NodeAbstractResource) WriteResourceState(ctx EvalContext, addr addrs.Ab
 	return nil
 }
 
+func (n *NodeAbstractResource) ReadResourceInstanceState(ctx EvalContext, addr addrs.AbsResourceInstance) (*states.ResourceInstanceObject, error) {
+	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
+
+	if provider == nil {
+		panic("ReadResourceInstanceState used with no Provider object")
+	}
+	if providerSchema == nil {
+		panic("ReadResourceInstanceState used with no ProviderSchema object")
+	}
+
+	log.Printf("[TRACE] ReadResourceInstanceState: reading state for %s", addr)
+
+	src := ctx.State().ResourceInstanceObject(addr, states.CurrentGen)
+	if src == nil {
+		// Presumably we only have deposed objects, then.
+		log.Printf("[TRACE] ReadResourceInstanceState: no state present for %s", addr)
+		return nil, nil
+	}
+
+	schema, currentVersion := (providerSchema).SchemaForResourceAddr(addr.Resource.ContainingResource())
+	if schema == nil {
+		// Shouldn't happen since we should've failed long ago if no schema is present
+		return nil, fmt.Errorf("no schema available for %s while reading state; this is a bug in Terraform and should be reported", addr)
+	}
+	var diags tfdiags.Diagnostics
+	src, diags = UpgradeResourceState(addr, provider, src, schema, currentVersion)
+	if diags.HasErrors() {
+		// Note that we don't have any channel to return warnings here. We'll
+		// accept that for now since warnings during a schema upgrade would
+		// be pretty weird anyway, since this operation is supposed to seem
+		// invisible to the user.
+		return nil, diags.Err()
+	}
+
+	obj, err := src.Decode(schema.ImpliedType())
+	if err != nil {
+		return nil, err
+	}
+
+	return obj, nil
+}
+
 // graphNodesAreResourceInstancesInDifferentInstancesOfSameModule is an
 // annoyingly-task-specific helper function that returns true if and only if
 // the following conditions hold:
diff --git a/terraform/node_resource_destroy.go b/terraform/node_resource_destroy.go
index 70533ca7f..7b1a2f580 100644
--- a/terraform/node_resource_destroy.go
+++ b/terraform/node_resource_destroy.go
@@ -170,13 +170,7 @@ func (n *NodeDestroyResourceInstance) Execute(ctx EvalContext, op walkOperation)
 			return EvalEarlyExitError{}
 		}
 
-		evalReadState := &EvalReadState{
-			Addr:           addr.Resource,
-			Output:         &state,
-			Provider:       &provider,
-			ProviderSchema: &providerSchema,
-		}
-		_, err = evalReadState.Eval(ctx)
+		state, err = n.ReadResourceInstanceState(ctx, addr)
 		if err != nil {
 			return err
 		}
diff --git a/terraform/node_resource_plan_orphan.go b/terraform/node_resource_plan_orphan.go
index bbff235a5..53884534f 100644
--- a/terraform/node_resource_plan_orphan.go
+++ b/terraform/node_resource_plan_orphan.go
@@ -35,19 +35,12 @@ func (n *NodePlannableResourceInstanceOrphan) Execute(ctx EvalContext, op walkOp
 	var change *plans.ResourceInstanceChange
 	var state *states.ResourceInstanceObject
 
-	provider, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
+	_, providerSchema, err := GetProvider(ctx, n.ResolvedProvider)
 	if err != nil {
 		return err
 	}
 
-	//EvalReadState
-	readState := &EvalReadState{
-		Addr:           addr.Resource,
-		Provider:       &provider,
-		ProviderSchema: &providerSchema,
-		Output:         &state,
-	}
-	_, err = readState.Eval(ctx)
+	state, err = n.ReadResourceInstanceState(ctx, addr)
 	if err != nil {
 		return err
 	}