still moving codebase to new API (WIP)

vendor/github.com/jmoiron/sqlx/reflectx/reflect.go

@@ -1,5 +1,5 @@
 // Package reflectx implements extensions to the standard reflect lib suitable
-// for implementing marshaling and unmarshaling packages.  The main Mapper type
+// for implementing marshalling and unmarshalling packages.  The main Mapper type
 // allows for Go-compatible named attribute access, including accessing embedded
 // struct attributes and the ability to use  functions and struct tags to
 // customize field names.
@@ -7,14 +7,13 @@
 package reflectx
 
 import (
-	"fmt"
 	"reflect"
 	"runtime"
 	"strings"
 	"sync"
 )
 
-// A FieldInfo is a collection of metadata about a struct field.
+// A FieldInfo is metadata for a struct field.
 type FieldInfo struct {
 	Index    []int
 	Path     string
@@ -41,7 +40,8 @@ func (f StructMap) GetByPath(path string) *FieldInfo {
 }
 
 // GetByTraversal returns a *FieldInfo for a given integer path.  It is
-// analogous to reflect.FieldByIndex.
+// analogous to reflect.FieldByIndex, but using the cached traversal
+// rather than re-executing the reflect machinery each time.
 func (f StructMap) GetByTraversal(index []int) *FieldInfo {
 	if len(index) == 0 {
 		return nil
@@ -58,8 +58,8 @@ func (f StructMap) GetByTraversal(index []int) *FieldInfo {
 }
 
 // Mapper is a general purpose mapper of names to struct fields.  A Mapper
-// behaves like most marshallers, optionally obeying a field tag for name
-// mapping and a function to provide a basic mapping of fields to names.
+// behaves like most marshallers in the standard library, obeying a field tag
+// for name mapping but also providing a basic transform function.
 type Mapper struct {
 	cache      map[reflect.Type]*StructMap
 	tagName    string
@@ -68,8 +68,8 @@ type Mapper struct {
 	mutex      sync.Mutex
 }
 
-// NewMapper returns a new mapper which optionally obeys the field tag given
-// by tagName.  If tagName is the empty string, it is ignored.
+// NewMapper returns a new mapper using the tagName as its struct field tag.
+// If tagName is the empty string, it is ignored.
 func NewMapper(tagName string) *Mapper {
 	return &Mapper{
 		cache:   make(map[reflect.Type]*StructMap),
@@ -127,7 +127,7 @@ func (m *Mapper) FieldMap(v reflect.Value) map[string]reflect.Value {
 	return r
 }
 
-// FieldByName returns a field by the its mapped name as a reflect.Value.
+// FieldByName returns a field by its mapped name as a reflect.Value.
 // Panics if v's Kind is not Struct or v is not Indirectable to a struct Kind.
 // Returns zero Value if the name is not found.
 func (m *Mapper) FieldByName(v reflect.Value, name string) reflect.Value {
@@ -182,11 +182,12 @@ func (m *Mapper) TraversalsByName(t reflect.Type, names []string) [][]int {
 	return r
 }
 
-// FieldByIndexes returns a value for a particular struct traversal.
+// FieldByIndexes returns a value for the field given by the struct traversal
+// for the given value.
 func FieldByIndexes(v reflect.Value, indexes []int) reflect.Value {
 	for _, i := range indexes {
 		v = reflect.Indirect(v).Field(i)
-		// if this is a pointer, it's possible it is nil
+		// if this is a pointer and it's nil, allocate a new value and set it
 		if v.Kind() == reflect.Ptr && v.IsNil() {
 			alloc := reflect.New(Deref(v.Type()))
 			v.Set(alloc)
@@ -225,13 +226,12 @@ type kinder interface {
 // mustBe checks a value against a kind, panicing with a reflect.ValueError
 // if the kind isn't that which is required.
 func mustBe(v kinder, expected reflect.Kind) {
-	k := v.Kind()
-	if k != expected {
+	if k := v.Kind(); k != expected {
 		panic(&reflect.ValueError{Method: methodName(), Kind: k})
 	}
 }
 
-// methodName is returns the caller of the function calling methodName
+// methodName returns the caller of the function calling methodName
 func methodName() string {
 	pc, _, _, _ := runtime.Caller(2)
 	f := runtime.FuncForPC(pc)
@@ -257,19 +257,92 @@ func apnd(is []int, i int) []int {
 	return x
 }
 
+type mapf func(string) string
+
+// parseName parses the tag and the target name for the given field using
+// the tagName (eg 'json' for `json:"foo"` tags), mapFunc for mapping the
+// field's name to a target name, and tagMapFunc for mapping the tag to
+// a target name.
+func parseName(field reflect.StructField, tagName string, mapFunc, tagMapFunc mapf) (tag, fieldName string) {
+	// first, set the fieldName to the field's name
+	fieldName = field.Name
+	// if a mapFunc is set, use that to override the fieldName
+	if mapFunc != nil {
+		fieldName = mapFunc(fieldName)
+	}
+
+	// if there's no tag to look for, return the field name
+	if tagName == "" {
+		return "", fieldName
+	}
+
+	// if this tag is not set using the normal convention in the tag,
+	// then return the fieldname..  this check is done because according
+	// to the reflect documentation:
+	//    If the tag does not have the conventional format,
+	//    the value returned by Get is unspecified.
+	// which doesn't sound great.
+	if !strings.Contains(string(field.Tag), tagName+":") {
+		return "", fieldName
+	}
+
+	// at this point we're fairly sure that we have a tag, so lets pull it out
+	tag = field.Tag.Get(tagName)
+
+	// if we have a mapper function, call it on the whole tag
+	// XXX: this is a change from the old version, which pulled out the name
+	// before the tagMapFunc could be run, but I think this is the right way
+	if tagMapFunc != nil {
+		tag = tagMapFunc(tag)
+	}
+
+	// finally, split the options from the name
+	parts := strings.Split(tag, ",")
+	fieldName = parts[0]
+
+	return tag, fieldName
+}
+
+// parseOptions parses options out of a tag string, skipping the name
+func parseOptions(tag string) map[string]string {
+	parts := strings.Split(tag, ",")
+	options := make(map[string]string, len(parts))
+	if len(parts) > 1 {
+		for _, opt := range parts[1:] {
+			// short circuit potentially expensive split op
+			if strings.Contains(opt, "=") {
+				kv := strings.Split(opt, "=")
+				options[kv[0]] = kv[1]
+				continue
+			}
+			options[opt] = ""
+		}
+	}
+	return options
+}
+
 // getMapping returns a mapping for the t type, using the tagName, mapFunc and
 // tagMapFunc to determine the canonical names of fields.
-func getMapping(t reflect.Type, tagName string, mapFunc, tagMapFunc func(string) string) *StructMap {
+func getMapping(t reflect.Type, tagName string, mapFunc, tagMapFunc mapf) *StructMap {
 	m := []*FieldInfo{}
 
 	root := &FieldInfo{}
 	queue := []typeQueue{}
 	queue = append(queue, typeQueue{Deref(t), root, ""})
 
+QueueLoop:
 	for len(queue) != 0 {
 		// pop the first item off of the queue
 		tq := queue[0]
 		queue = queue[1:]
+
+		// ignore recursive field
+		for p := tq.fi.Parent; p != nil; p = p.Parent {
+			if tq.fi.Field.Type == p.Field.Type {
+				continue QueueLoop
+			}
+		}
+
 		nChildren := 0
 		if tq.t.Kind() == reflect.Struct {
 			nChildren = tq.t.NumField()
@@ -278,53 +351,31 @@ func getMapping(t reflect.Type, tagName string, mapFunc, tagMapFunc func(string)
 
 		// iterate through all of its fields
 		for fieldPos := 0; fieldPos < nChildren; fieldPos++ {
+
 			f := tq.t.Field(fieldPos)
 
-			fi := FieldInfo{}
-			fi.Field = f
-			fi.Zero = reflect.New(f.Type).Elem()
-			fi.Options = map[string]string{}
-
-			var tag, name string
-			if tagName != "" && strings.Contains(string(f.Tag), tagName+":") {
-				tag = f.Tag.Get(tagName)
-				name = tag
-			} else {
-				if mapFunc != nil {
-					name = mapFunc(f.Name)
-				}
-			}
-
-			parts := strings.Split(name, ",")
-			if len(parts) > 1 {
-				name = parts[0]
-				for _, opt := range parts[1:] {
-					kv := strings.Split(opt, "=")
-					if len(kv) > 1 {
-						fi.Options[kv[0]] = kv[1]
-					} else {
-						fi.Options[kv[0]] = ""
-					}
-				}
-			}
-
-			if tagMapFunc != nil {
-				tag = tagMapFunc(tag)
-			}
-
-			fi.Name = name
-
-			if tq.pp == "" || (tq.pp == "" && tag == "") {
-				fi.Path = fi.Name
-			} else {
-				fi.Path = fmt.Sprintf("%s.%s", tq.pp, fi.Name)
-			}
+			// parse the tag and the target name using the mapping options for this field
+			tag, name := parseName(f, tagName, mapFunc, tagMapFunc)
 
 			// if the name is "-", disabled via a tag, skip it
 			if name == "-" {
 				continue
 			}
 
+			fi := FieldInfo{
+				Field:   f,
+				Name:    name,
+				Zero:    reflect.New(f.Type).Elem(),
+				Options: parseOptions(tag),
+			}
+
+			// if the path is empty this path is just the name
+			if tq.pp == "" {
+				fi.Path = fi.Name
+			} else {
+				fi.Path = tq.pp + "." + fi.Name
+			}
+
 			// skip unexported fields
 			if len(f.PkgPath) != 0 && !f.Anonymous {
 				continue