Added anchor operator

pkg/yqlib/doc/Anchor Operators.md

@@ -0,0 +1,29 @@
+
+## Get anchor
+Given a sample.yml file of:
+```yaml
+a: &billyBob cat
+```
+then
+```bash
+yq eval '.a | anchor' sample.yml
+```
+will output
+```yaml
+billyBob
+```
+
+## Set anchor name
+Given a sample.yml file of:
+```yaml
+a: cat
+```
+then
+```bash
+yq eval '.a anchor = "foobar"' sample.yml
+```
+will output
+```yaml
+a: &foobar cat
+```
+

pkg/yqlib/lib.go

@@ -36,6 +36,7 @@ var AssignAttributes = &OperationType{Type: "ASSIGN_ATTRIBUTES", NumArgs: 2, Pre
 var AssignStyle = &OperationType{Type: "ASSIGN_STYLE", NumArgs: 2, Precedence: 40, Handler: AssignStyleOperator}
 var AssignTag = &OperationType{Type: "ASSIGN_TAG", NumArgs: 2, Precedence: 40, Handler: AssignTagOperator}
 var AssignComment = &OperationType{Type: "ASSIGN_COMMENT", NumArgs: 2, Precedence: 40, Handler: AssignCommentsOperator}
+var AssignAnchor = &OperationType{Type: "ASSIGN_ANCHOR", NumArgs: 2, Precedence: 40, Handler: AssignAnchorOperator}
 
 var Multiply = &OperationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: MultiplyOperator}
 var Add = &OperationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: AddOperator}
@@ -51,6 +52,7 @@ var Collect = &OperationType{Type: "COLLECT", NumArgs: 0, Precedence: 50, Handle
 var GetStyle = &OperationType{Type: "GET_STYLE", NumArgs: 0, Precedence: 50, Handler: GetStyleOperator}
 var GetTag = &OperationType{Type: "GET_TAG", NumArgs: 0, Precedence: 50, Handler: GetTagOperator}
 var GetComment = &OperationType{Type: "GET_COMMENT", NumArgs: 0, Precedence: 50, Handler: GetCommentsOperator}
+var GetAnchor = &OperationType{Type: "GET_ANCHOR", NumArgs: 0, Precedence: 50, Handler: GetAnchorOperator}
 var GetDocumentIndex = &OperationType{Type: "GET_DOCUMENT_INDEX", NumArgs: 0, Precedence: 50, Handler: GetDocumentIndexOperator}
 var GetFilename = &OperationType{Type: "GET_FILENAME", NumArgs: 0, Precedence: 50, Handler: GetFilenameOperator}
 var GetFileIndex = &OperationType{Type: "GET_FILE_INDEX", NumArgs: 0, Precedence: 50, Handler: GetFileIndexOperator}

pkg/yqlib/operator_anchor_name.go

@@ -0,0 +1,48 @@
+package yqlib
+
+import (
+	"container/list"
+
+	"gopkg.in/yaml.v3"
+)
+
+func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+
+	log.Debugf("AssignAnchor operator!")
+
+	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if err != nil {
+		return nil, err
+	}
+	anchorName := ""
+	if rhs.Front() != nil {
+		anchorName = rhs.Front().Value.(*CandidateNode).Node.Value
+	}
+
+	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+
+	if err != nil {
+		return nil, err
+	}
+
+	for el := lhs.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		log.Debugf("Setting anchorName of : %v", candidate.GetKey())
+		candidate.Node.Anchor = anchorName
+	}
+	return matchingNodes, nil
+}
+
+func GetAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+	log.Debugf("GetAnchor operator!")
+	var results = list.New()
+
+	for el := matchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		anchor := candidate.Node.Anchor
+		node := &yaml.Node{Kind: yaml.ScalarNode, Value: anchor, Tag: "!!str"}
+		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
+		results.PushBack(lengthCand)
+	}
+	return results, nil
+}

pkg/yqlib/operator_anchor_name_test.go

@@ -0,0 +1,31 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var anchorOperatorScenarios = []expressionScenario{
+	{
+		description: "Get anchor",
+		document:    `a: &billyBob cat`,
+		expression:  `.a | anchor`,
+		expected: []string{
+			"D0, P[a], (!!str)::billyBob\n",
+		},
+	},
+	{
+		description: "Set anchor name",
+		document:    `a: cat`,
+		expression:  `.a anchor = "foobar"`,
+		expected: []string{
+			"D0, P[], (doc)::a: &foobar cat\n",
+		},
+	},
+}
+
+func TestAnchorOperatorScenarios(t *testing.T) {
+	for _, tt := range anchorOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Anchor Operators", anchorOperatorScenarios)
+}

pkg/yqlib/path_tokeniser.go

@@ -208,6 +208,7 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`style`), opAssignableToken(GetStyle, AssignStyle))
 
 	lexer.Add([]byte(`tag`), opAssignableToken(GetTag, AssignTag))
+	lexer.Add([]byte(`anchor`), opAssignableToken(GetAnchor, AssignAnchor))
 	lexer.Add([]byte(`filename`), opToken(GetFilename))
 	lexer.Add([]byte(`fileIndex`), opToken(GetFileIndex))
 	lexer.Add([]byte(`path`), opToken(GetPath))