filling values is now recursive

args.go

@@ -8,7 +8,7 @@ import (
 )
 
 func parseArgs(args []string, dest interface{}) (*Object, error) {
-	reqs, err := requirements(dest)
+	reqs, err := requirements(reflect.TypeOf(dest))
 	if err != nil {
 		return nil, fmt.Errorf("unable to parse args: bad requirements: %s", err)
 	}
@@ -125,7 +125,7 @@ func parseArgs(args []string, dest interface{}) (*Object, error) {
 }
 
 func showHelp(dest interface{}) {
-	reqs, err := requirements(dest)
+	reqs, err := requirements(reflect.TypeOf(dest))
 	if err != nil {
 		panic(err)
 	}

object.go

@@ -122,32 +122,69 @@ func (o *Object) Fill(dest interface{}) error {
 	// dt = destination type
 	dt := reflect.TypeOf(dest)
 	if dt.Kind() != reflect.Ptr {
-		return fmt.Errorf("destination is of type %v; a pointer type is required", dt)
+		return fmt.Errorf("destination is of type %v (%v); a pointer type is required", dt, dt.Kind())
+	}
+
+	// ensure the pointer points to a struct type
+	if dt.Elem().Kind() != reflect.Struct {
+		return fmt.Errorf("destination is a pointer to a non-struct type: %v (pointer to struct required)", dt.Elem())
 	}
 
-	reqs, err := requirements(dest)
+	// value of our struct pointer
+	pv := reflect.ValueOf(dest)
+
+	// value of the struct being pointed to
+	v := pv.Elem()
+
+	return o.fillValue(v)
+}
+
+func (o *Object) fillValue(dv reflect.Value) error {
+	switch dv.Kind() {
+	case reflect.Struct:
+		// this is fine
+	case reflect.Ptr:
+		if dv.IsNil() {
+			dv.Set(reflect.New(dv.Type().Elem()))
+		}
+		dv = reflect.Indirect(dv)
+	default:
+		return fmt.Errorf("moon object can only fillValue to a struct value, saw %v (%v)", dv.Type(), dv.Kind())
+	}
+
+	// the destination defines the requirements (i.e., the method of unpacking
+	// our moon data)
+	reqs, err := requirements(dv.Type())
 	if err != nil {
-		return fmt.Errorf("unable to gather requirements: %s", err)
+		return fmt.Errorf("unable to gather requirements: %v", err)
 	}
 
-	// dv = destination value
-	dv := reflect.ValueOf(dest).Elem()
 	for fname, req := range reqs {
-		// fv = field value
+		// field value
 		fv := dv.FieldByName(fname)
-		v, ok := o.items[req.name]
+		// object value
-		if ok {
+		ov, ok := o.items[req.name]
-			if !fv.Type().AssignableTo(reflect.TypeOf(v)) {
+		if !ok {
-				return fmt.Errorf("unable to assign field %s: source type %v is not assignable to destination type %v", req.name, fv.Type(), reflect.TypeOf(v))
+			// moon data is missing expected field
-			}
-			fv.Set(reflect.ValueOf(v))
-		} else {
 			if req.required {
+				// if the field is required, that's an error
 				return fmt.Errorf("required field missing: %s", fname)
 			}
 			if req.d_fault != nil {
+				// otherwise, we look for a user-defined default value
 				fv.Set(reflect.ValueOf(req.d_fault))
 			}
+			continue
+		}
+
+		switch t_ov := ov.(type) {
+		case *Object:
+			return t_ov.fillValue(fv)
+		default:
+			if !fv.Type().AssignableTo(reflect.TypeOf(ov)) {
+				return fmt.Errorf("unable to assign field %s: source type %v is not assignable to destination type %v", req.name, reflect.TypeOf(ov), fv.Type())
+			}
+			fv.Set(reflect.ValueOf(ov))
 		}
 	}
 	return nil

object_test.go

@@ -141,23 +141,32 @@ func ExampleDoc_Get_two() {
 	// Output: sean
 }
 
-// func TestFillEmbeds(t *testing.T) {
+func TestFillEmbeds(t *testing.T) {
-// 	in := `top: {val: some_data}`
+	in := `top: {val: some_data}`
-//
+
-// 	var dest struct {
+	var dest struct {
-// 		Top *struct {
+		Top *struct {
-// 			Val string `name: val`
+			Val string `name: val`
-// 		} `name: top`
+		} `name: top`
-// 	}
+	}
-//
+
-// 	doc, err := ReadString(in)
+	doc, err := ReadString(in)
-// 	if err != nil {
+	if err != nil {
-// 		t.Error(err)
+		t.Error(err)
-// 		return
+		return
-// 	}
+	}
-//
+
-// 	if err := doc.Fill(&dest); err != nil {
+	if err := doc.Fill(&dest); err != nil {
-// 		t.Error(err)
+		t.Error(err)
-// 		return
+		return
-// 	}
+	}
-// }
+
+	if dest.Top == nil {
+		t.Error("didn't actually set a value")
+		return
+	}
+
+	if dest.Top.Val != "some_data" {
+		t.Errorf("expected some_data, got %v", dest.Top.Val)
+	}
+}

req.go

@@ -87,18 +87,22 @@ func field2req(field reflect.StructField) (*req, error) {
 	return &req, nil
 }
 
-func requirements(dest interface{}) (map[string]req, error) {
+// requirements gathers the moon requirements for a given struct type. the
-	dt := reflect.TypeOf(dest)
+// output is a mapping of field names to requirements.
-	if dt.Kind() != reflect.Ptr {
+func requirements(t reflect.Type) (map[string]req, error) {
-		return nil, fmt.Errorf("destination is of type %v; a pointer type is required", dt)
+	switch t.Kind() {
+	case reflect.Ptr:
+		t = t.Elem()
+	case reflect.Struct:
+	default:
+		return nil, fmt.Errorf("destination is of type %v; a pointer or struct type is required", t)
 	}
 
-	dv := reflect.ValueOf(dest).Elem()
+	n := t.NumField()
-	n := dv.NumField()
+	out := make(map[string]req, t.NumField())
-	out := make(map[string]req, dv.NumField())
 
 	for i := 0; i < n; i++ {
-		field := dv.Type().Field(i)
+		field := t.Field(i)
 		req, err := field2req(field)
 		if err != nil {
 			return nil, fmt.Errorf("unable to gather requirements for field %s: %s", field.Name, err)