requirements parsing

this shit is really brittle

lib/doc.go

@@ -81,16 +81,9 @@ func (d *Doc) Get(path string, dest interface{}) error {
 
 	dv := reflect.ValueOf(dest)
 	dve := dv.Elem()
-	return setValue(dve, reflect.ValueOf(v))
-}
-
-func setValue(dest, src reflect.Value) error {
-	if dest.Type() == src.Type() {
-		dest.Set(src)
+	dve.Set(reflect.ValueOf(v))
 	return nil
 }
-	return fmt.Errorf("src and destination are not of same type. src type: %s, dest type: %s", src.Type().Name(), dest.Type().Name())
-}
 
 // Fill takes the raw values from the moon document and assigns them to the
 // struct pointed at by dest.  Dest must be a struct pointer; any other type
@@ -101,45 +94,25 @@ func (d *Doc) Fill(dest interface{}) error {
 		return fmt.Errorf("destination is of type %v; a pointer type is required", dt)
 	}
 
-	dv := reflect.ValueOf(dest).Elem()
-
-	n := dv.NumField()
-	for i := 0; i < n; i++ {
-		field, fv := dv.Type().Field(i), dv.Field(i)
-
-		tag := field.Tag
-		fopts, err := ReadString(string(tag))
+	reqs, err := requirements(dest)
 	if err != nil {
-			return fmt.Errorf("unable to parse options for type %s, field %s: %s",
-				dv.Type().Name(), field.Name, err)
-		}
-
-		var fname string
-		if err := fopts.Get("name", &fname); err != nil {
-			if _, ok := err.(NoValue); !ok {
-				return err
-			}
-		}
-
-		var frequired bool
-		if err := fopts.Get("required", &frequired); err != nil {
-			if _, ok := err.(NoValue); !ok {
-				return err
-			}
+		return fmt.Errorf("unable to gather requirements: %s", err)
 	}
 
-		fdefault := fopts.items["default"]
-
-		v, ok := d.items[fname]
-		if !ok {
-			if frequired {
-				return fmt.Errorf("required field missing: %s", fname)
+	dv := reflect.ValueOf(dest).Elem()
+	for fname, req := range reqs {
+		fv := dv.FieldByName(fname)
+		v, ok := d.items[req.name]
+		if ok {
+			fv.Set(reflect.ValueOf(v))
 		} else {
-				fv.Set(reflect.ValueOf(fdefault))
-				continue
+			if req.required {
+				return fmt.Errorf("required field missing: %s", fname)
+			}
+			if req.d_fault != nil {
+				fv.Set(reflect.ValueOf(req.d_fault))
 			}
 		}
-		fv.Set(reflect.ValueOf(v))
 	}
 	return nil
 }

lib/doc_test.go

@@ -41,6 +41,7 @@ func TestFill(t *testing.T) {
 
 	if err := doc.Fill(&dest); err != nil {
 		t.Error(err)
+		return
 	}
 
 	if dest.FirstName != "jordan" {

lib/req.go

@@ -0,0 +1,92 @@
+package moon
+
+import (
+	"fmt"
+	"reflect"
+)
+
+type req struct {
+	name     string      // name as it appears in moon config file.  Defaults to the field name.
+	cliName  string      // name as it appears on the command line
+	help     string      // text given in help documentation
+	required bool        // whether or not the option must be configured
+	d_fault  interface{} // default value for when the option is missing
+	short    string      // short flag on the command line
+	long     string      // long flag on the command line
+	flag     bool        // whether or not the variable is a flag.
+	t        reflect.Type
+}
+
+func (r req) validate() error {
+	if r.name == "" {
+		return fmt.Errorf("invalid requirement: requirement must have a name")
+	}
+
+	if r.required && r.flag {
+		return fmt.Errorf("invalid requirement %s: a flag cannot be required", r.name)
+	}
+
+	if r.required && r.d_fault != nil {
+		return fmt.Errorf("invalid requirement %s: a required value cannot have a default", r.name)
+	}
+
+	return nil
+}
+
+func field2req(field reflect.StructField) (*req, error) {
+	doc, err := ReadString(string(field.Tag))
+	if err != nil {
+		return nil, fmt.Errorf("unable to parse requirements for field %s: %s", field.Name, err)
+	}
+
+	req := req{
+		name:    field.Name,
+		cliName: field.Name,
+		t:       field.Type,
+	}
+	// it's really easy to cause infinite recursion here, since this is used by
+	// some of the higher up functions, so we're going to hack the document directly
+
+	errors := map[string]error{
+		"name":     doc.Get("name", &req.name),
+		"cli_name": doc.Get("cli_name", &req.cliName),
+		"help":     doc.Get("help", &req.help),
+		"required": doc.Get("required", &req.required),
+		"default":  doc.Get("default", &req.d_fault),
+		"short":    doc.Get("short", &req.short),
+		"long":     doc.Get("long", &req.long),
+		"flag":     doc.Get("flag", &req.flag),
+	}
+
+	for fname, err := range errors {
+		if err == nil {
+			continue
+		}
+		if _, ok := err.(NoValue); !ok {
+			return nil, fmt.Errorf("unable to parse requirement %s: %s", fname, err)
+		}
+	}
+
+	return &req, nil
+}
+
+func requirements(dest interface{}) (map[string]req, error) {
+	dt := reflect.TypeOf(dest)
+	if dt.Kind() != reflect.Ptr {
+		return nil, fmt.Errorf("destination is of type %v; a pointer type is required", dt)
+	}
+
+	dv := reflect.ValueOf(dest).Elem()
+	n := dv.NumField()
+	out := make(map[string]req, dv.NumField())
+
+	for i := 0; i < n; i++ {
+		field := dv.Type().Field(i)
+		req, err := field2req(field)
+		if err != nil {
+			return nil, fmt.Errorf("unable to gather requireents for field %s: %s", field.Name, err)
+		}
+		out[field.Name] = *req
+	}
+	return out, nil
+}