terraform: guard output types. Fixes #593

terraform/context.go

@@ -550,7 +550,14 @@ func (c *walkContext) Walk() error {
 			}
 		}
 		if vraw != nil {
-			outputs[o.Name] = vraw.(string)
+			if list, ok := vraw.([]interface{}); ok {
+				vraw = list[0]
+			}
+			if s, ok := vraw.(string); ok {
+				outputs[o.Name] = s
+			} else {
+				return fmt.Errorf("Type of output '%s' is not a string: %#v", o.Name, vraw)
+			}
 		}
 	}
 

terraform/context_test.go

@@ -2416,6 +2416,55 @@ func TestContextApply_output(t *testing.T) {
 	}
 }
 
+func TestContextApply_outputInvalid(t *testing.T) {
+	m := testModule(t, "apply-output-invalid")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	_, err := ctx.Plan(nil)
+	if err == nil {
+		t.Fatalf("err: %s", err)
+	}
+	if !strings.Contains(err.Error(), "is not a string") {
+		t.Fatalf("err: %s", err)
+	}
+}
+
+func TestContextApply_outputList(t *testing.T) {
+	m := testModule(t, "apply-output-list")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	if _, err := ctx.Plan(nil); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actual := strings.TrimSpace(state.String())
+	expected := strings.TrimSpace(testTerraformApplyOutputListStr)
+	if actual != expected {
+		t.Fatalf("bad: \n%s", actual)
+	}
+}
+
 func TestContextApply_outputMulti(t *testing.T) {
 	m := testModule(t, "apply-output-multi")
 	p := testProvider("aws")

terraform/terraform_test.go

@@ -377,6 +377,29 @@ Outputs:
 foo_num = 2
 `
 
+const testTerraformApplyOutputListStr = `
+aws_instance.bar.0:
+  ID = foo
+  foo = bar
+  type = aws_instance
+aws_instance.bar.1:
+  ID = foo
+  foo = bar
+  type = aws_instance
+aws_instance.bar.2:
+  ID = foo
+  foo = bar
+  type = aws_instance
+aws_instance.foo:
+  ID = foo
+  num = 2
+  type = aws_instance
+
+Outputs:
+
+foo_num = bar,bar,bar
+`
+
 const testTerraformApplyOutputMultiStr = `
 aws_instance.bar.0:
   ID = foo

terraform/test-fixtures/apply-output-invalid/main.tf

@@ -0,0 +1,12 @@
+resource "aws_instance" "foo" {
+    num = "2"
+}
+
+resource "aws_instance" "bar" {
+    foo = "bar"
+    count = 3
+}
+
+output "foo_num" {
+    value = 42
+}

terraform/test-fixtures/apply-output-list/main.tf

@@ -0,0 +1,12 @@
+resource "aws_instance" "foo" {
+    num = "2"
+}
+
+resource "aws_instance" "bar" {
+    foo = "bar"
+    count = 3
+}
+
+output "foo_num" {
+    value = ["${join(",", aws_instance.bar.*.foo)}"]
+}