terraform: module computed vars with splat vars don't error

terraform/context_test.go

@@ -1935,6 +1935,23 @@ func TestContext2Refresh_targetedCountIndex(t *testing.T) {
 	}
 }
 
+func TestContext2Refresh_moduleComputedVar(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "refresh-module-computed-var")
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	// This was failing (see GH-2188) at some point, so this test just
+	// verifies that the failure goes away.
+	if _, err := ctx.Refresh(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+}
+
 func TestContext2Refresh_delete(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "refresh-basic")

terraform/interpolate.go

@@ -437,6 +437,14 @@ func (i *Interpolater) computeResourceMultiVariable(
 	}
 
 	if len(values) == 0 {
+		// If the operation is refresh, it isn't an error for a value to
+		// be unknown. Instead, we return that the value is computed so
+		// that the graph can continue to refresh other nodes. It doesn't
+		// matter because the config isn't interpolated anyways.
+		if i.Operation == walkRefresh {
+			return config.UnknownVariableValue, nil
+		}
+
 		return "", fmt.Errorf(
 			"Resource '%s' does not have attribute '%s' "+
 				"for variable '%s'",

terraform/test-fixtures/refresh-module-computed-var/child/main.tf

@@ -0,0 +1,5 @@
+variable "value" {}
+
+output "value" {
+    value = "${var.value}"
+}

terraform/test-fixtures/refresh-module-computed-var/main.tf

@@ -0,0 +1,8 @@
+module "child" {
+    source = "./child"
+    value = "${join(" ", aws_instance.test.*.id)}"
+}
+
+resource "aws_instance" "test" {
+    value = "yes"
+}