From 3f090df26ea56c26ac6122a285e51056fcbd2cd1 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 13 Sep 2016 10:56:37 -0700
Subject: [PATCH] terraform: start apply-based graph builder, basic diff
 transform

---
 terraform/graph_builder_apply.go      | 44 +++++++++++++++++++++
 terraform/graph_builder_apply_test.go | 57 +++++++++++++++++++++++++++
 terraform/node_resource.go            | 10 +++++
 terraform/transform_diff.go           | 53 +++++++++++++++++++++++++
 4 files changed, 164 insertions(+)
 create mode 100644 terraform/graph_builder_apply.go
 create mode 100644 terraform/graph_builder_apply_test.go
 create mode 100644 terraform/node_resource.go
 create mode 100644 terraform/transform_diff.go

diff --git a/terraform/graph_builder_apply.go b/terraform/graph_builder_apply.go
new file mode 100644
index 000000000..f5f84d719
--- /dev/null
+++ b/terraform/graph_builder_apply.go
@@ -0,0 +1,44 @@
+package terraform
+
+import (
+	"github.com/hashicorp/terraform/config/module"
+)
+
+// ApplyGraphBuilder implements GraphBuilder and is responsible for building
+// a graph for applying a Terraform diff.
+//
+// Because the graph is built from the diff (vs. the config or state),
+// this helps ensure that the apply-time graph doesn't modify any resources
+// that aren't explicitly in the diff. There are other scenarios where the
+// diff can be deviated, so this is just one layer of protection.
+type ApplyGraphBuilder struct {
+	// Config is the root module for the graph to build.
+	Config *module.Tree
+
+	// Diff is the diff to apply.
+	Diff *Diff
+
+	// Providers is the list of providers supported.
+	Providers []string
+
+	// Provisioners is the list of provisioners supported.
+	Provisioners []string
+}
+
+// See GraphBuilder
+func (b *ApplyGraphBuilder) Build(path []string) (*Graph, error) {
+	return (&BasicGraphBuilder{
+		Steps:    b.Steps(),
+		Validate: true,
+	}).Build(path)
+}
+
+// See GraphBuilder
+func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
+	steps := []GraphTransformer{
+		// Creates all the nodes represented in the diff.
+		&DiffTransformer{Diff: b.Diff},
+	}
+
+	return steps
+}
diff --git a/terraform/graph_builder_apply_test.go b/terraform/graph_builder_apply_test.go
new file mode 100644
index 000000000..45d4c95bc
--- /dev/null
+++ b/terraform/graph_builder_apply_test.go
@@ -0,0 +1,57 @@
+package terraform
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestApplyGraphBuilder_impl(t *testing.T) {
+	var _ GraphBuilder = new(ApplyGraphBuilder)
+}
+
+func TestApplyGraphBuilder(t *testing.T) {
+	diff := &Diff{
+		Modules: []*ModuleDiff{
+			&ModuleDiff{
+				Path: []string{"root"},
+				Resources: map[string]*InstanceDiff{
+					// Verify noop doesn't show up in graph
+					"aws_instance.noop": &InstanceDiff{},
+
+					"aws_instance.create": &InstanceDiff{
+						Attributes: map[string]*ResourceAttrDiff{
+							"name": &ResourceAttrDiff{
+								Old: "",
+								New: "foo",
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	b := &ApplyGraphBuilder{
+		Diff: diff,
+	}
+
+	g, err := b.Build(RootModulePath)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if !reflect.DeepEqual(g.Path, RootModulePath) {
+		t.Fatalf("bad: %#v", g.Path)
+	}
+
+	actual := strings.TrimSpace(g.String())
+	expected := strings.TrimSpace(testApplyGraphBuilderStr)
+	if actual != expected {
+		t.Fatalf("bad: %s", actual)
+	}
+}
+
+const testApplyGraphBuilderStr = `
+aws_instance.create
+`
diff --git a/terraform/node_resource.go b/terraform/node_resource.go
new file mode 100644
index 000000000..86dd245f2
--- /dev/null
+++ b/terraform/node_resource.go
@@ -0,0 +1,10 @@
+package terraform
+
+// NodeResource is a graph node for referencing a resource.
+type NodeResource struct {
+	Addr *ResourceAddress // Addr is the address for this resource
+}
+
+func (n *NodeResource) Name() string {
+	return n.Addr.String()
+}
diff --git a/terraform/transform_diff.go b/terraform/transform_diff.go
new file mode 100644
index 000000000..e51834629
--- /dev/null
+++ b/terraform/transform_diff.go
@@ -0,0 +1,53 @@
+package terraform
+
+import (
+	"fmt"
+)
+
+// DiffTransformer is a GraphTransformer that adds the elements of
+// the diff to the graph.
+//
+// This transform is used for example by the ApplyGraphBuilder to ensure
+// that only resources that are being modified are represented in the graph.
+type DiffTransformer struct {
+	Diff *Diff
+}
+
+func (t *DiffTransformer) Transform(g *Graph) error {
+	// If the diff is nil or empty (nil is empty) then do nothing
+	if t.Diff.Empty() {
+		return nil
+	}
+
+	// Go through all the modules in the diff.
+	for _, m := range t.Diff.Modules {
+		// TODO: If this is a destroy diff then add a module destroy node
+
+		// Go through all the resources in this module.
+		for name, inst := range m.Resources {
+			// TODO: Destroy diff
+
+			// If this diff has no attribute changes, then we have
+			// nothing to do and therefore won't add it to the graph.
+			if len(inst.Attributes) == 0 {
+				continue
+			}
+
+			// We have changes! This is a create or update operation.
+			// First grab the address so we have a unique way to
+			// reference this resource.
+			addr, err := parseResourceAddressInternal(name)
+			if err != nil {
+				return fmt.Errorf(
+					"Error parsing internal name, this is a bug: %q", name)
+			}
+
+			// Add the resource to the graph
+			g.Add(&NodeResource{
+				Addr: addr,
+			})
+		}
+	}
+
+	return nil
+}