Fixed recursive decent on empty objects/arrays

pkg/yqlib/doc/Add.md

@@ -2,6 +2,7 @@ Add behaves differently according to the type of the LHS:
 - arrays: concatenate
 - number scalars: arithmetic addition (soon)
 - string scalars: concatenate (soon)
+
 ## Concatenate arrays
 Given a sample.yml file of:
 ```yaml

pkg/yqlib/lib.go

@@ -17,6 +17,7 @@ type OperationType struct {
 }
 
 // operators TODO:
+// - cookbook doc for common things
 // - write in place
 // - mergeAppend (merges and appends arrays)
 // - mergeEmpty (sets only if the document is empty, do I do that now?)
@@ -70,9 +71,6 @@ var Select = &OperationType{Type: "SELECT", NumArgs: 1, Precedence: 50, Handler:
 var Has = &OperationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler: HasOperator}
 var DeleteChild = &OperationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: DeleteChildOperator}
 
-// var Exists = &OperationType{Type: "Length", NumArgs: 2, Precedence: 35}
-// filters matches if they have the existing path
-
 type Operation struct {
 	OperationType *OperationType
 	Value         interface{}

pkg/yqlib/operator_multiply_test.go

@@ -13,6 +13,13 @@ var multiplyOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!map)::{a: {also: me}, b: {also: me}}\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		expression: `{} * {"cat":"dog"}`,
+		expected: []string{
+			"D0, P[], (!!map)::cat: dog\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		document:   `{a: {also: me}, b: {also: [1]}}`,

pkg/yqlib/operator_recursive_descent.go

@@ -26,7 +26,7 @@ func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.Li
 		log.Debugf("Recursive Decent, added %v", NodeToString(candidate))
 		results.PushBack(candidate)
 
-		if candidate.Node.Kind != yaml.AliasNode {
+		if candidate.Node.Kind != yaml.AliasNode && len(candidate.Node.Content) > 0 {
 
 			children, err := Splat(d, nodeToMap(candidate))
 

pkg/yqlib/operator_recursive_descent_test.go

@@ -5,6 +5,22 @@ import (
 )
 
 var recursiveDescentOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		document:   `{}`,
+		expression: `..`,
+		expected: []string{
+			"D0, P[], (!!map)::{}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[]`,
+		expression: `..`,
+		expected: []string{
+			"D0, P[], (!!seq)::[]\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		document:   `cat`,