From eb88ccbc7b5dbd223f2e8df6c1a571b42fca633d Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Wed, 26 Oct 2022 12:04:08 -0400
Subject: [PATCH] only add NoOp nodes with conditions

ONly add NoOp changes to the apply graph if they have conditions which
need to be evaluated.
---
 internal/terraform/graph_builder_apply.go |  1 +
 internal/terraform/transform_diff.go      | 26 ++++++++++++++-
 internal/terraform/transform_diff_test.go | 39 +++++++++++++++++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/internal/terraform/graph_builder_apply.go b/internal/terraform/graph_builder_apply.go
index 4d7763d2a5..22f1b8c3bc 100644
--- a/internal/terraform/graph_builder_apply.go
+++ b/internal/terraform/graph_builder_apply.go
@@ -107,6 +107,7 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 			Concrete: concreteResourceInstance,
 			State:    b.State,
 			Changes:  b.Changes,
+			Config:   b.Config,
 		},
 
 		// Attach the state
diff --git a/internal/terraform/transform_diff.go b/internal/terraform/transform_diff.go
index bfabf60e9f..3bce1131f5 100644
--- a/internal/terraform/transform_diff.go
+++ b/internal/terraform/transform_diff.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"log"
 
+	"github.com/hashicorp/terraform/internal/addrs"
+	"github.com/hashicorp/terraform/internal/configs"
 	"github.com/hashicorp/terraform/internal/dag"
 	"github.com/hashicorp/terraform/internal/plans"
 	"github.com/hashicorp/terraform/internal/states"
@@ -16,6 +18,28 @@ type DiffTransformer struct {
 	Concrete ConcreteResourceInstanceNodeFunc
 	State    *states.State
 	Changes  *plans.Changes
+	Config   *configs.Config
+}
+
+// return true if the given resource instance has either Preconditions or
+// Postconditions defined in the configuration.
+func (t *DiffTransformer) hasConfigConditions(addr addrs.AbsResourceInstance) bool {
+	// unit tests may have no config
+	if t.Config == nil {
+		return false
+	}
+
+	cfg := t.Config.DescendentForInstance(addr.Module)
+	if cfg == nil {
+		return false
+	}
+
+	res := cfg.Module.ResourceByAddr(addr.ConfigResource().Resource)
+	if res == nil {
+		return false
+	}
+
+	return len(res.Preconditions) > 0 || len(res.Postconditions) > 0
 }
 
 func (t *DiffTransformer) Transform(g *Graph) error {
@@ -69,7 +93,7 @@ func (t *DiffTransformer) Transform(g *Graph) error {
 			// run any condition checks associated with the object, to
 			// make sure that they still hold when considering the
 			// results of other changes.
-			update = true
+			update = t.hasConfigConditions(addr)
 		case plans.Delete:
 			delete = true
 		case plans.DeleteThenCreate, plans.CreateThenDelete:
diff --git a/internal/terraform/transform_diff_test.go b/internal/terraform/transform_diff_test.go
index c7cddc452f..fa1feae34d 100644
--- a/internal/terraform/transform_diff_test.go
+++ b/internal/terraform/transform_diff_test.go
@@ -81,6 +81,26 @@ func TestDiffTransformer_noOpChange(t *testing.T) {
 	// results changed even if the resource instance they are attached to
 	// didn't actually change directly itself.
 
+	// aws_instance.foo has a precondition, so should be included in the final
+	// graph. aws_instance.bar has no conditions, so there is nothing to
+	// execute during apply and it should not be included in the graph.
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+resource "aws_instance" "bar" {
+}
+
+resource "aws_instance" "foo" {
+  test_string = "ok"
+
+  lifecycle {
+	precondition {
+		condition     = self.test_string != ""
+		error_message = "resource error"
+	}
+  }
+}
+`})
+
 	g := Graph{Path: addrs.RootModuleInstance}
 
 	beforeVal, err := plans.NewDynamicValue(cty.StringVal(""), cty.String)
@@ -89,6 +109,7 @@ func TestDiffTransformer_noOpChange(t *testing.T) {
 	}
 
 	tf := &DiffTransformer{
+		Config: m,
 		Changes: &plans.Changes{
 			Resources: []*plans.ResourceInstanceChangeSrc{
 				{
@@ -109,6 +130,24 @@ func TestDiffTransformer_noOpChange(t *testing.T) {
 						After:  beforeVal,
 					},
 				},
+				{
+					Addr: addrs.Resource{
+						Mode: addrs.ManagedResourceMode,
+						Type: "aws_instance",
+						Name: "bar",
+					}.Instance(addrs.NoKey).Absolute(addrs.RootModuleInstance),
+					ProviderAddr: addrs.AbsProviderConfig{
+						Provider: addrs.NewDefaultProvider("aws"),
+						Module:   addrs.RootModule,
+					},
+					ChangeSrc: plans.ChangeSrc{
+						// A "no-op" change has the no-op action and has the
+						// same object as both Before and After.
+						Action: plans.NoOp,
+						Before: beforeVal,
+						After:  beforeVal,
+					},
+				},
 			},
 		},
 	}