config: determine whether a variable is required properly

config/config.go

@@ -14,7 +14,7 @@ import (
 type Config struct {
 	ProviderConfigs map[string]*ProviderConfig
 	Resources       []*Resource
-	Variables       map[string]Variable
+	Variables       map[string]*Variable
 }
 
 // ProviderConfig is the configuration for a resource provider.
@@ -36,9 +36,11 @@ type Resource struct {
 	Variables map[string]InterpolatedVariable
 }
 
+// Variable is a variable defined within the configuration.
 type Variable struct {
 	Default     string
 	Description string
+	defaultSet  bool
 }
 
 // An InterpolatedVariable is a variable that is embedded within a string
@@ -130,6 +132,11 @@ func (c *Config) ResourceGraph() *depgraph.Graph {
 	}
 }
 
+// Required tests whether a variable is required or not.
+func (v *Variable) Required() bool {
+	return !v.defaultSet
+}
+
 func NewResourceVariable(key string) (*ResourceVariable, error) {
 	parts := strings.SplitN(key, ".", 3)
 	return &ResourceVariable{

config/loader_libucl.go

@@ -23,18 +23,39 @@ func (t *libuclConfigurable) Close() error {
 }
 
 func (t *libuclConfigurable) Config() (*Config, error) {
+	type LibuclVariable struct {
+		Default     string
+		Description string
+		Fields      []string `libucl:",decodedFields"`
+	}
+
 	var rawConfig struct {
-		Variable map[string]Variable
+		Variable map[string]*LibuclVariable
 	}
 
 	if err := t.Object.Decode(&rawConfig); err != nil {
 		return nil, err
 	}
 
-	// Start building up the actual configuration. We first
-	// copy the fields that can be directly assigned.
+	// Start building up the actual configuration. We start with
+	// variables.
 	config := new(Config)
-	config.Variables = rawConfig.Variable
+	config.Variables = make(map[string]*Variable)
+	for k, v := range rawConfig.Variable {
+		defaultSet := false
+		for _, f := range v.Fields {
+			if f == "Default" {
+				defaultSet = true
+				break
+			}
+		}
+
+		config.Variables[k] = &Variable{
+			Default:     v.Default,
+			Description: v.Description,
+			defaultSet:  defaultSet,
+		}
+	}
 
 	// Build the provider configs
 	providers := t.Object.Get("provider")

config/loader_test.go

@@ -66,6 +66,31 @@ func TestLoadBasic_import(t *testing.T) {
 	}
 }
 
+func TestLoad_variables(t *testing.T) {
+	c, err := Load(filepath.Join(fixtureDir, "variables.tf"))
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	if c == nil {
+		t.Fatal("config should not be nil")
+	}
+
+	actual := variablesStr(c.Variables)
+	if actual != strings.TrimSpace(variablesVariablesStr) {
+		t.Fatalf("bad:\n%s", actual)
+	}
+
+	if !c.Variables["foo"].Required() {
+		t.Fatal("foo should be required")
+	}
+	if c.Variables["bar"].Required() {
+		t.Fatal("bar should not be required")
+	}
+	if c.Variables["baz"].Required() {
+		t.Fatal("baz should not be required")
+	}
+}
+
 // This helper turns a provider configs field into a deterministic
 // string value for comparison in tests.
 func providerConfigsStr(pcs map[string]*ProviderConfig) string {
@@ -135,7 +160,7 @@ func resourcesStr(rs []*Resource) string {
 
 // This helper turns a variables field into a deterministic
 // string value for comparison in tests.
-func variablesStr(vs map[string]Variable) string {
+func variablesStr(vs map[string]*Variable) string {
 	result := ""
 	for k, v := range vs {
 		if v.Default == "" {
@@ -199,3 +224,15 @@ foo
   bar
   bar
 `
+
+const variablesVariablesStr = `
+foo
+  <>
+  <>
+bar
+  <>
+  <>
+baz
+  foo
+  <>
+`

config/test-fixtures/variables.tf

@@ -0,0 +1,7 @@
+variable "foo" {}
+variable "bar" {
+    default = ""
+}
+variable "baz" {
+    default = "foo"
+}