terraform: validate required variables are all set

terraform/terraform.go

@@ -30,6 +30,27 @@ type Config struct {
 // time, as well as richer checks such as verifying that the resource providers
 // can be properly initialized, can be configured, etc.
 func New(c *Config) (*Terraform, error) {
+	// Validate that all required variables have values
+	required := make(map[string]struct{})
+	for k, v := range c.Config.Variables {
+		if v.Required() {
+			required[k] = struct{}{}
+		}
+	}
+	for k, _ := range c.Variables {
+		delete(required, k)
+	}
+	if len(required) > 0 {
+		errs := make([]error, 0, len(required))
+		for k, _ := range required {
+			errs = append(errs, fmt.Errorf(
+				"Required variable not set: %s", k))
+		}
+
+		// TODO(mitchellh): Return multi-error
+		return nil, errs[0]
+	}
+
 	// Go through each resource and match it up to a provider
 	mapping := make(map[*config.Resource]ResourceProvider)
 	providers := make(map[string]ResourceProvider)

terraform/terraform_test.go

@@ -79,3 +79,47 @@ func TestNew(t *testing.T) {
 		t.Fatalf("bad: %#v", mapping)
 	}
 }
+
+func TestNew_variables(t *testing.T) {
+	config := testConfig(t, "new-variables")
+	tfConfig := &Config{
+		Config: config,
+	}
+
+	// Missing
+	tfConfig.Variables = map[string]string{
+		"bar": "baz",
+	}
+	tf, err := New(tfConfig)
+	if err == nil {
+		t.Fatal("should error")
+	}
+	if tf != nil {
+		t.Fatalf("should not return tf")
+	}
+
+	// Good
+	tfConfig.Variables = map[string]string{
+		"foo": "bar",
+	}
+	tf, err = New(tfConfig)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if tf == nil {
+		t.Fatal("tf should not be nil")
+	}
+
+	// Good
+	tfConfig.Variables = map[string]string{
+		"foo": "bar",
+		"bar": "baz",
+	}
+	tf, err = New(tfConfig)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if tf == nil {
+		t.Fatal("tf should not be nil")
+	}
+}

terraform/test-fixtures/new-variables/main.tf

@@ -0,0 +1,4 @@
+variable "foo" {}
+variable "bar" {
+    default = "baz"
+}