diff: show properly fufilled variables if possible

diff/resource_builder.go

@@ -30,6 +30,9 @@ func (b *ResourceBuilder) Diff(
 	// Go through the configuration and find the changed attributes
 	for k, v := range c.Raw {
 		newV := v.(string)
+		if cleanV, ok := c.Config[k]; ok {
+			newV = cleanV.(string)
+		}
 
 		var oldV string
 		var ok bool

diff/resource_builder_test.go

@@ -3,6 +3,7 @@ package diff
 import (
 	"testing"
 
+	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -90,6 +91,59 @@ func TestResourceBuilder_same(t *testing.T) {
 	}
 }
 
+func TestResourceBuilder_unknown(t *testing.T) {
+	rb := &ResourceBuilder{}
+
+	state := &terraform.ResourceState{}
+
+	c := testConfig(t, map[string]interface{}{
+		"foo": "${var.unknown}",
+	}, map[string]string{
+		"var.foo":     "bar",
+		"var.unknown": config.UnknownVariableValue,
+	})
+
+	diff, err := rb.Diff(state, c)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if diff == nil {
+		t.Fatal("should not be nil")
+	}
+
+	actual := testResourceDiffStr(diff)
+	expected := testRBUnknownDiff
+	if actual != expected {
+		t.Fatalf("bad: %s", actual)
+	}
+}
+
+func TestResourceBuilder_vars(t *testing.T) {
+	rb := &ResourceBuilder{}
+
+	state := &terraform.ResourceState{}
+
+	c := testConfig(t, map[string]interface{}{
+		"foo": "${var.foo}",
+	}, map[string]string{
+		"var.foo": "bar",
+	})
+
+	diff, err := rb.Diff(state, c)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if diff == nil {
+		t.Fatal("should not be nil")
+	}
+
+	actual := testResourceDiffStr(diff)
+	expected := testRBVarsDiff
+	if actual != expected {
+		t.Fatalf("bad: %s", actual)
+	}
+}
+
 const testRBNewDiff = `CREATE
   foo:        "" => "bar"
   id:         "" => "<computed>" (forces new resource)
@@ -101,3 +155,13 @@ const testRBRequiresNewDiff = `CREATE
   id:         "1" => "<computed>" (forces new resource)
   private_ip: "127.0.0.1" => "<computed>"
 `
+
+const testRBUnknownDiff = `CREATE
+  foo: "" => "${var.unknown}"
+  id:  "" => "<computed>" (forces new resource)
+`
+
+const testRBVarsDiff = `CREATE
+  foo: "" => "bar"
+  id:  "" => "<computed>" (forces new resource)
+`