terraform: set count to 1 while validating [GH-442]

terraform/context.go

@@ -1034,18 +1034,20 @@ func (c *walkContext) validateWalkFn() depgraph.WalkFunc {
 				// Interpolate the count and verify it is non-negative
 				rc := NewResourceConfig(rn.Config.RawCount)
 				rc.interpolate(c, rn.Resource)
-				count, err := rn.Config.Count()
-				if err == nil {
-					if count < 0 {
-						err = fmt.Errorf(
-							"%s error: count must be positive", rn.Resource.Id)
+				if !rc.IsComputed(rn.Config.RawCount.Key) {
+					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
 					}
-				}
-				if err != nil {
-					l.Lock()
-					defer l.Unlock()
-					meta.Errs = append(meta.Errs, err)
-					return nil
 				}
 
 				return c.genericWalkResource(rn, walkFn)
@@ -1269,6 +1271,20 @@ func (c *walkContext) genericWalkResource(
 	rc := NewResourceConfig(rn.Config.RawCount)
 	rc.interpolate(c, rn.Resource)
 
+	// If we're validating, then we set the count to 1 if it is computed
+	if c.Operation == walkValidate {
+		if key := rn.Config.RawCount.Key; rc.IsComputed(key) {
+			// Preserve the old value so that we reset it properly
+			old := rn.Config.RawCount.Raw[key]
+			defer func() {
+				rn.Config.RawCount.Raw[key] = old
+			}()
+
+			// Set th count to 1 for validation purposes
+			rn.Config.RawCount.Raw[key] = "1"
+		}
+	}
+
 	// Expand the node to the actual resources
 	g, err := rn.Expand()
 	if err != nil {

terraform/context_test.go

@@ -149,6 +149,28 @@ func TestContextValidate_countVariable(t *testing.T) {
 	}
 }
 
+func TestContextValidate_countVariableNoDefault(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "validate-count-variable")
+	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) > 1 {
+		for _, err := range e {
+			t.Errorf("bad: %s", err)
+		}
+		t.FailNow()
+	}
+}
+
 func TestContextValidate_moduleBadResource(t *testing.T) {
 	m := testModule(t, "validate-module-bad-rc")
 	p := testProvider("aws")

terraform/test-fixtures/validate-count-variable/main.tf

@@ -0,0 +1,6 @@
+variable "foo" {}
+
+resource "aws_instance" "foo" {
+    foo = "foo"
+    count = "${var.foo}"
+}