Add status code 103 Early Hints. Add the ability to customize and change the order of controller's fields and their registered valid dependencies relative to: #1343

Former-commit-id: 5bd9e02e5fafca135d17cad87f4a9aec526b333b

hero/di/di.go

@@ -33,6 +33,7 @@ func Struct(s interface{}, values ...reflect.Value) *StructInjector {
 		ValueOf(s),
 		DefaultHijacker,
 		DefaultTypeChecker,
+		SortByNumMethods,
 		Values(values).CloneWithFieldsOf(s)...,
 	)
 }
@@ -64,6 +65,7 @@ type D struct {
 
 	hijacker Hijacker
 	goodFunc TypeChecker
+	sorter   Sorter
 }
 
 // New creates and returns a new Dependency Injection container.
@@ -85,13 +87,20 @@ func (d *D) GoodFunc(fn TypeChecker) *D {
 	return d
 }
 
+// Sort sets the fields and valid bindable values sorter for struct injection.
+func (d *D) Sort(with Sorter) *D {
+	d.sorter = with
+	return d
+}
+
 // Clone returns a new Dependency Injection container, it adopts the
-// parent's (current "D") hijacker, good func type checker and all dependencies values.
+// parent's (current "D") hijacker, good func type checker, sorter and all dependencies values.
 func (d *D) Clone() *D {
 	return &D{
 		Values:   d.Values.Clone(),
 		hijacker: d.hijacker,
 		goodFunc: d.goodFunc,
+		sorter:   d.sorter,
 	}
 }
 
@@ -108,6 +117,7 @@ func (d *D) Struct(s interface{}) *StructInjector {
 		ValueOf(s),
 		d.hijacker,
 		d.goodFunc,
+		d.sorter,
 		d.Values.CloneWithFieldsOf(s)...,
 	)
 }

hero/di/reflect.go

@@ -178,11 +178,6 @@ type field struct {
 	Name   string // the actual name.
 	Index  []int  // the index of the field, slice if it's part of a embedded struct
 	CanSet bool   // is true if it's exported.
-
-	// this could be empty, but in our cases it's not,
-	// it's filled with the bind object (as service which means as static value)
-	// and it's filled from the lookupFields' caller.
-	AnyValue reflect.Value
 }
 
 // NumFields returns the total number of fields, and the embedded, even if the embedded struct is not exported,

hero/di/struct.go

@@ -3,6 +3,7 @@ package di
 import (
 	"fmt"
 	"reflect"
+	"sort"
 )
 
 // Scope is the struct injector's struct value scope/permant state.
@@ -40,6 +41,8 @@ type (
 	targetStructField struct {
 		Object     *BindObject
 		FieldIndex []int
+		// ValueIndex is used mostly for debugging, it's the order of the registered binded value targets to that field.
+		ValueIndex int
 	}
 
 	// StructInjector keeps the data that are needed in order to do the binding injection
@@ -68,13 +71,37 @@ func (s *StructInjector) countBindType(typ BindType) (n int) {
 	return
 }
 
+// Sorter is the type for sort customization of a struct's fields
+// and its available bindable values.
+//
+// Sorting applies only when a field can accept more than one registered value.
+type Sorter func(t1 reflect.Type, t2 reflect.Type) bool
+
+// SortByNumMethods is a builtin sorter to sort fields and values
+// based on their type and its number of methods, highest number of methods goes first.
+//
+// It is the default sorter on package-level struct injector function `Struct`.
+var SortByNumMethods Sorter = func(t1 reflect.Type, t2 reflect.Type) bool {
+	if t1.Kind() != t2.Kind() {
+		return true
+	}
+
+	if k := t1.Kind(); k == reflect.Interface || k == reflect.Struct {
+		return t1.NumMethod() > t2.NumMethod()
+	} else if k != reflect.Struct {
+		return false // non-structs goes last.
+	}
+
+	return true
+}
+
 // MakeStructInjector returns a new struct injector, which will be the object
 // that the caller should use to bind exported fields or
 // embedded unexported fields that contain exported fields
 // of the "v" struct value or pointer.
 //
 // The hijack and the goodFunc are optional, the "values" is the dependencies collection.
-func MakeStructInjector(v reflect.Value, hijack Hijacker, goodFunc TypeChecker, values ...reflect.Value) *StructInjector {
+func MakeStructInjector(v reflect.Value, hijack Hijacker, goodFunc TypeChecker, sorter Sorter, values ...reflect.Value) *StructInjector {
 	s := &StructInjector{
 		initRef:        v,
 		initRefAsSlice: []reflect.Value{v},
@@ -96,7 +123,19 @@ func MakeStructInjector(v reflect.Value, hijack Hijacker, goodFunc TypeChecker,
 
 	visited := make(map[int]struct{}, 0) // add a visited to not add twice a single value (09-Jul-2019).
 	fields := lookupFields(s.elemType, true, nil)
+
+	// for idx, val := range values {
+	// 	  fmt.Printf("[%d] value type [%s] value name [%s]\n", idx, val.Type().String(), val.String())
+	// }
+
+	if len(fields) > 1 && sorter != nil {
+		sort.Slice(fields, func(i, j int) bool {
+			return sorter(fields[i].Type, fields[j].Type)
+		})
+	}
+
 	for _, f := range fields {
+		// fmt.Printf("[%d] field type [%s] value name [%s]\n", idx, f.Type.String(), f.Name)
 		if hijack != nil {
 			if b, ok := hijack(f.Type); ok && b != nil {
 				s.fields = append(s.fields, &targetStructField{
@@ -108,6 +147,8 @@ func MakeStructInjector(v reflect.Value, hijack Hijacker, goodFunc TypeChecker,
 			}
 		}
 
+		var possibleValues []*targetStructField
+
 		for idx, val := range values {
 			if _, alreadySet := visited[idx]; alreadySet {
 				continue
@@ -120,15 +161,33 @@ func MakeStructInjector(v reflect.Value, hijack Hijacker, goodFunc TypeChecker,
 			}
 
 			if b.IsAssignable(f.Type) {
-				visited[idx] = struct{}{}
-				// fmt.Printf("bind the object to the field: %s at index: %#v and type: %s\n", f.Name, f.Index, f.Type.String())
-				s.fields = append(s.fields, &targetStructField{
+				possibleValues = append(possibleValues, &targetStructField{
+					ValueIndex: idx,
 					FieldIndex: f.Index,
 					Object:     &b,
 				})
-				break
 			}
 		}
+
+		if l := len(possibleValues); l == 0 {
+			continue
+		} else if l > 1 && sorter != nil {
+			sort.Slice(possibleValues, func(i, j int) bool {
+				// if first.Object.BindType != second.Object.BindType {
+				// 	return true
+				// }
+
+				// if first.Object.BindType != Static { // dynamic goes last.
+				// 	return false
+				// }
+				return sorter(possibleValues[i].Object.Type, possibleValues[j].Object.Type)
+			})
+		}
+
+		tf := possibleValues[0]
+		visited[tf.ValueIndex] = struct{}{}
+		// fmt.Printf("bind the object to the field: %s at index: %#v and type: %s\n", f.Name, f.Index, f.Type.String())
+		s.fields = append(s.fields, tf)
 	}
 
 	s.Has = len(s.fields) > 0