From e4ba7373924237f3554578f9613ddd027160c0fa Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Thu, 2 Oct 2014 17:14:25 -0700
Subject: [PATCH] terraform: validate count is non-negative

---
 terraform/context.go                          | 17 +++++++++++++++++
 terraform/context_test.go                     | 19 +++++++++++++++++++
 .../validate-count-negative/main.tf           |  3 +++
 3 files changed, 39 insertions(+)
 create mode 100644 terraform/test-fixtures/validate-count-negative/main.tf

diff --git a/terraform/context.go b/terraform/context.go
index a8894a73f..5dd2d2f05 100644
--- a/terraform/context.go
+++ b/terraform/context.go
@@ -991,6 +991,23 @@ func (c *walkContext) validateWalkFn() depgraph.WalkFunc {
 
 			// If we're expanding, then expand the nodes, and then rewalk the graph
 			if rn.ExpandMode > ResourceExpandNone {
+				// Interpolate the count and verify it is non-negative
+				rc := NewResourceConfig(rn.Config.RawCount)
+				rc.interpolate(c)
+				count, err := rn.Config.Count()
+				if err == nil {
+					if count < 0 {
+						err = fmt.Errorf(
+							"%s error: count must be positive", rn.Resource.Id)
+					}
+				}
+				if err != nil {
+					l.Lock()
+					defer l.Unlock()
+					meta.Errs = append(meta.Errs, err)
+					return nil
+				}
+
 				return c.genericWalkResource(rn, walkFn)
 			}
 
diff --git a/terraform/context_test.go b/terraform/context_test.go
index b4ea97824..d44c499c2 100644
--- a/terraform/context_test.go
+++ b/terraform/context_test.go
@@ -107,6 +107,25 @@ func TestContextValidate_badVar(t *testing.T) {
 	}
 }
 
+func TestContextValidate_countNegative(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "validate-count-negative")
+	c := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	w, e := c.Validate()
+	if len(w) > 0 {
+		t.Fatalf("bad: %#v", w)
+	}
+	if len(e) == 0 {
+		t.Fatalf("bad: %#v", e)
+	}
+}
+
 func TestContextValidate_moduleBadResource(t *testing.T) {
 	m := testModule(t, "validate-module-bad-rc")
 	p := testProvider("aws")
diff --git a/terraform/test-fixtures/validate-count-negative/main.tf b/terraform/test-fixtures/validate-count-negative/main.tf
new file mode 100644
index 000000000..d5bb04653
--- /dev/null
+++ b/terraform/test-fixtures/validate-count-negative/main.tf
@@ -0,0 +1,3 @@
+resource "aws_instance" "test" {
+    count = "-5"
+}