From 23fa3107a3f1cd8a3b330c32b8030fad6f9ddb57 Mon Sep 17 00:00:00 2001
From: Sylvia Moss <moss@hashicorp.com>
Date: Thu, 13 Feb 2020 17:35:23 +0100
Subject: [PATCH] Render variables one time on prepare method (#8727)

---
 builder/null/artifact_export.go               |  5 +++
 builder/null/builder.go                       |  1 +
 command/build_test.go                         | 32 ++++++++++++++++++-
 .../build-variable-sharing/template.json      | 25 +++++++++++++++
 packer/provisioner.go                         |  7 ++++
 template/interpolate/i.go                     |  7 +++-
 template/interpolate/render.go                |  2 +-
 7 files changed, 76 insertions(+), 3 deletions(-)
 create mode 100644 command/test-fixtures/build-variable-sharing/template.json

diff --git a/builder/null/artifact_export.go b/builder/null/artifact_export.go
index 3962358e0..e3d23236d 100644
--- a/builder/null/artifact_export.go
+++ b/builder/null/artifact_export.go
@@ -25,6 +25,11 @@ func (a *NullArtifact) String() string {
 }
 
 func (a *NullArtifact) State(name string) interface{} {
+	if name == "generated_data" {
+		return map[interface{}]interface{}{
+			"ID": "Null",
+		}
+	}
 	return nil
 }
 
diff --git a/builder/null/builder.go b/builder/null/builder.go
index e0568ce05..1d2fc40e4 100644
--- a/builder/null/builder.go
+++ b/builder/null/builder.go
@@ -47,6 +47,7 @@ func (b *Builder) Run(ctx context.Context, ui packer.Ui, hook packer.Hook) (pack
 	state := new(multistep.BasicStateBag)
 	state.Put("hook", hook)
 	state.Put("ui", ui)
+	state.Put("instance_id", "Null")
 
 	// Run!
 	b.runner = common.NewRunner(steps, b.config.PackerConfig, ui)
diff --git a/command/build_test.go b/command/build_test.go
index ca8252715..76e49d65a 100644
--- a/command/build_test.go
+++ b/command/build_test.go
@@ -111,6 +111,33 @@ func TestBuildOnlyFileMultipleFlags(t *testing.T) {
 	}
 }
 
+func TestBuildProvisionAndPosProcessWithBuildVariablesSharing(t *testing.T) {
+	c := &BuildCommand{
+		Meta: testMetaFile(t),
+	}
+
+	args := []string{
+		filepath.Join(testFixture("build-variable-sharing"), "template.json"),
+	}
+
+	files := []string{
+		"provisioner.Null.txt",
+		"post-processor.Null.txt",
+	}
+
+	defer cleanup(files...)
+
+	if code := c.Run(args); code != 0 {
+		fatalCommand(t, c.Meta)
+	}
+
+	for _, f := range files {
+		if !fileExists(f) {
+			t.Errorf("Expected to find %s", f)
+		}
+	}
+}
+
 func TestBuildEverything(t *testing.T) {
 	c := &BuildCommand{
 		Meta: testMetaFile(t),
@@ -231,7 +258,7 @@ func testMetaFile(t *testing.T) Meta {
 	}
 }
 
-func cleanup() {
+func cleanup(moreFiles ...string) {
 	os.RemoveAll("chocolate.txt")
 	os.RemoveAll("vanilla.txt")
 	os.RemoveAll("cherry.txt")
@@ -245,6 +272,9 @@ func cleanup() {
 	os.RemoveAll("lilas.txt")
 	os.RemoveAll("campanules.txt")
 	os.RemoveAll("ducky.txt")
+	for _, file := range moreFiles {
+		os.RemoveAll(file)
+	}
 }
 
 func TestBuildCommand_ParseArgs(t *testing.T) {
diff --git a/command/test-fixtures/build-variable-sharing/template.json b/command/test-fixtures/build-variable-sharing/template.json
new file mode 100644
index 000000000..ac1c410b5
--- /dev/null
+++ b/command/test-fixtures/build-variable-sharing/template.json
@@ -0,0 +1,25 @@
+{
+    "builders": [
+        {
+            "name": "chocolate",
+            "type": "null",
+            "communicator": "none"
+        }
+    ],
+    "provisioners": [
+        {
+            "type": "shell-local",
+            "inline": [
+                "echo hi > provisioner.{{ build `ID`}}.txt"
+            ]
+        }
+    ],
+    "post-processors": [
+        {
+            "type": "shell-local",
+            "inline": [
+                "echo hi > post-processor.{{ build `ID`}}.txt"
+            ]
+        }
+    ]
+}
\ No newline at end of file
diff --git a/packer/provisioner.go b/packer/provisioner.go
index fce6355f3..7b7fdaa60 100644
--- a/packer/provisioner.go
+++ b/packer/provisioner.go
@@ -80,6 +80,13 @@ func BasicPlaceholderData() map[string]string {
 }
 
 func CastDataToMap(data interface{}) map[string]interface{} {
+
+	if interMap, ok := data.(map[string]interface{}); ok {
+		// null and file builder sometimes don't use a communicator and
+		// therefore don't go through RPC
+		return interMap
+	}
+
 	// Provisioners expect a map[string]interface{} in their data field, but
 	// it gets converted into a map[interface]interface on the way over the
 	// RPC. Check that data can be cast into such a form, and cast it.
diff --git a/template/interpolate/i.go b/template/interpolate/i.go
index 9dcdc4ba8..54d1e516e 100644
--- a/template/interpolate/i.go
+++ b/template/interpolate/i.go
@@ -44,7 +44,12 @@ func NewContext() *Context {
 	return &Context{}
 }
 
-// Render is shorthand for constructing an I and calling Render.
+// RenderOnce is shorthand for constructing an I and calling Render one time.
+func RenderOnce(v string, ctx *Context) (string, error) {
+	return (&I{Value: v}).Render(ctx)
+}
+
+// Render is shorthand for constructing an I and calling Render until all variables are rendered.
 func Render(v string, ctx *Context) (rendered string, err error) {
 	// Keep interpolating until all variables are done
 	// Sometimes a variable can been inside another one
diff --git a/template/interpolate/render.go b/template/interpolate/render.go
index 4c49d43b8..7893e8745 100644
--- a/template/interpolate/render.go
+++ b/template/interpolate/render.go
@@ -57,7 +57,7 @@ func RenderMap(v interface{}, ctx *Context, f *RenderFilter) (map[string]interfa
 // RenderInterface renders any value and returns the resulting value.
 func RenderInterface(v interface{}, ctx *Context) (interface{}, error) {
 	f := func(v string) (string, error) {
-		return Render(v, ctx)
+		return RenderOnce(v, ctx)
 	}
 
 	walker := &renderWalker{