core: Don't create self-references in state

Since StateReferences was implemented on NodeAbstractResource rather than
NodeAbstractResourceInstance it wasn't properly detecting references to
the same instance as self-references.

Now that we are using "seen" to filter out duplicates we can also simplify
how we handle these self-references by just pretending we saw them before
we even start the loop.

This change is confirmed by
TestContext2Apply_provisionerMultiSelfRefSingle

terraform/node_resource_abstract.go

@@ -270,7 +270,7 @@ func dottedInstanceAddr(tr addrs.ResourceInstance) string {
 
 // StateReferences returns the dependencies to put into the state for
 // this resource.
-func (n *NodeAbstractResource) StateReferences() []addrs.Referenceable {
+func (n *NodeAbstractResourceInstance) StateReferences() []addrs.Referenceable {
 	selfAddrs := n.ReferenceableAddrs()
 
 	// Since we don't include the source location references in our
@@ -279,6 +279,18 @@ func (n *NodeAbstractResource) StateReferences() []addrs.Referenceable {
 	// that additional context.
 	seen := map[string]struct{}{}
 
+	// Pretend that we've already "seen" all of our own addresses so that we
+	// won't record self-references in the state. This can arise if, for
+	// example, a provisioner for a resource refers to the resource itself,
+	// which is valid (since provisioners always run after apply) but should
+	// not create an explicit dependency edge.
+	for _, selfAddr := range selfAddrs {
+		seen[selfAddr.String()] = struct{}{}
+		if riAddr, ok := selfAddr.(addrs.ResourceInstance); ok {
+			seen[riAddr.ContainingResource().String()] = struct{}{}
+		}
+	}
+
 	depsRaw := n.References()
 	deps := make([]addrs.Referenceable, 0, len(depsRaw))
 	for _, d := range depsRaw {
@@ -300,17 +312,7 @@ func (n *NodeAbstractResource) StateReferences() []addrs.Referenceable {
 		case addrs.ResourceInstance:
 			deps = append(deps, tr)
 		case addrs.Resource:
-			depStr := tr.String()
-			selfRef := false
-			for _, selfAddr := range selfAddrs {
-				if selfAddr.String() == depStr {
-					selfRef = true
-					break
-				}
-			}
-			if !selfRef { // Don't create self-references
-				deps = append(deps, tr)
-			}
+			deps = append(deps, tr)
 		case addrs.ModuleCallInstance:
 			deps = append(deps, tr)
 		default:

terraform/terraform_test.go

@@ -726,7 +726,7 @@ aws_instance.foo.1:
   type = aws_instance
 
   Dependencies:
-    aws_instance.foo.0
+    aws_instance.foo[0]
 aws_instance.foo.2:
   ID = foo
   provider = provider.aws
@@ -734,7 +734,7 @@ aws_instance.foo.2:
   type = aws_instance
 
   Dependencies:
-    aws_instance.foo.0
+    aws_instance.foo[0]
 `
 
 const testTerraformApplyProvisionerDiffStr = `

terraform/test-fixtures/apply-provisioner-multi-self-ref-single/main.tf

@@ -1,9 +1,9 @@
 resource "aws_instance" "foo" {
-    count = 3
-    foo = "number ${count.index}"
+  count = 3
+  foo   = "number ${count.index}"
 
-    provisioner "shell" {
-        command = "${aws_instance.foo.0.foo}"
-         order  = "${count.index}"
-    }
+  provisioner "shell" {
+    command = aws_instance.foo[0].foo
+    order   = count.index
+  }
 }