Merge pull request #1949 from hashicorp/b-module-cbd-computed-count-deadlock

core: fix deadlock w/ CBD + modules

terraform/context_test.go

@@ -139,6 +139,56 @@ func TestContext2Plan_moduleCycle(t *testing.T) {
 	}
 }
 
+func TestContext2Plan_moduleDeadlock(t *testing.T) {
+	m := testModule(t, "plan-module-deadlock")
+	p := testProvider("aws")
+	p.DiffFn = testDiffFn
+	timeout := make(chan bool, 1)
+	done := make(chan bool, 1)
+	go func() {
+		time.Sleep(3 * time.Second)
+		timeout <- true
+	}()
+	go func() {
+		ctx := testContext2(t, &ContextOpts{
+			Module: m,
+			Providers: map[string]ResourceProviderFactory{
+				"aws": testProviderFuncFixed(p),
+			},
+		})
+
+		plan, err := ctx.Plan()
+		done <- true
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+
+		actual := strings.TrimSpace(plan.String())
+		expected := strings.TrimSpace(`
+DIFF:
+
+module.child:
+  CREATE: aws_instance.foo.0
+  CREATE: aws_instance.foo.1
+  CREATE: aws_instance.foo.2
+
+STATE:
+
+<no state>
+		`)
+		if actual != expected {
+			t.Fatalf("expected:\n%sgot:\n%s", expected, actual)
+		}
+	}()
+
+	select {
+	case <-timeout:
+		t.Fatalf("timed out! probably deadlock")
+	case <-done:
+		// ok
+	}
+}
+
 func TestContext2Plan_moduleInput(t *testing.T) {
 	m := testModule(t, "plan-module-input")
 	p := testProvider("aws")

terraform/graph_config_node_resource.go

@@ -311,6 +311,7 @@ func (n *GraphNodeConfigResourceFlat) DestroyNode(mode GraphNodeDestroyMode) Gra
 	return &graphNodeResourceDestroyFlat{
 		graphNodeResourceDestroy: node,
 		PathValue:                n.PathValue,
+		FlatCreateNode:           n,
 	}
 }
 
@@ -318,6 +319,9 @@ type graphNodeResourceDestroyFlat struct {
 	*graphNodeResourceDestroy
 
 	PathValue []string
+
+	// Needs to be able to properly yield back a flattened create node to prevent
+	FlatCreateNode *GraphNodeConfigResourceFlat
 }
 
 func (n *graphNodeResourceDestroyFlat) Name() string {
@@ -329,6 +333,10 @@ func (n *graphNodeResourceDestroyFlat) Path() []string {
 	return n.PathValue
 }
 
+func (n *graphNodeResourceDestroyFlat) CreateNode() dag.Vertex {
+	return n.FlatCreateNode
+}
+
 // graphNodeResourceDestroy represents the logical destruction of a
 // resource. This node doesn't mean it will be destroyed for sure, but
 // instead that if a destroy were to happen, it must happen at this point.

terraform/test-fixtures/plan-module-deadlock/child/main.tf

@@ -0,0 +1,4 @@
+resource "aws_instance" "foo" {
+  count = "${length("abc")}"
+  lifecycle { create_before_destroy = true }
+}

terraform/test-fixtures/plan-module-deadlock/main.tf

@@ -0,0 +1,3 @@
+module "child" {
+  source = "./child"
+}