adding comment and privatise func

extendeddatacrossword_test.go

@@ -443,7 +443,7 @@ func createTestEdsWithNMT(t *testing.T, codec Codec, shareSize, namespaceSize in
 		shares[i] = bytes.Repeat([]byte{byte(shareValue)}, shareSize)
 	}
 
-	treeConstructorFn, err := GetTreeConstructorFn("testing-tree")
+	treeConstructorFn, err := TreeFn("testing-tree")
 	require.NoError(t, err)
 
 	eds, err := ComputeExtendedDataSquare(shares, codec, treeConstructorFn)

extendeddatasquare.go

@@ -42,7 +42,7 @@ func (eds *ExtendedDataSquare) UnmarshalJSON(b []byte) error {
 		return err
 	}
 
-	treeConstructor, err := GetTreeConstructorFn(aux.Tree)
+	treeConstructor, err := TreeFn(aux.Tree)
 	if err != nil {
 		return err
 	}
@@ -77,7 +77,7 @@ func ComputeExtendedDataSquare(
 		return nil, err
 	}
 
-	treeName := GetTreeNameFromConstructorFn(treeCreatorFn)
+	treeName := getTreeNameFromConstructorFn(treeCreatorFn)
 	if treeName == "" {
 		return nil, errors.New("tree name not found")
 	}

tree.go

@@ -25,6 +25,7 @@ type Tree interface {
 // The keys of this map should be kebab cased. E.g. "default-tree"
 var trees = make(map[string]TreeConstructorFn)
 
+// Must be called in the init function
 func RegisterTree(treeName string, treeConstructor TreeConstructorFn) error {
 	if trees[treeName] != nil {
 		return fmt.Errorf("%s already registered", treeName)
@@ -34,15 +35,16 @@ func RegisterTree(treeName string, treeConstructor TreeConstructorFn) error {
 	return nil
 }
 
-func GetTreeConstructorFn(treeName string) (TreeConstructorFn, error) {
+// Get tree constructor function by tree name from the global map
+func TreeFn(treeName string) (TreeConstructorFn, error) {
 	if trees[treeName] == nil {
 		return nil, fmt.Errorf("%s not registered yet", treeName)
 	}
 
 	return trees[treeName], nil
 }
 
-func GetTreeNameFromConstructorFn(treeConstructor TreeConstructorFn) string {
+func getTreeNameFromConstructorFn(treeConstructor TreeConstructorFn) string {
 	key := ""
 	for k, v := range trees {
 		if reflect.DeepEqual(reflect.ValueOf(v), reflect.ValueOf(treeConstructor)) {