Added alias operator;

alias, anchor and explode ops are now all documented together

pkg/yqlib/doc/Anchor Operators.md

@@ -1,29 +0,0 @@
-
-## 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/doc/Anchor and Aliases Operators.md

@@ -1,4 +1,67 @@
-Explodes (or dereferences) aliases and anchors.
+Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference aliases and remove anchor names).
+
+`yq` supports merge aliases (like `<<: *blah`) however this is no longer in the standard yaml spec (1.2) and so `yq` will automatically add the `!!merge` tag to these nodes as it is effectively a custom tag.
+
+
+## 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
+Given a sample.yml file of:
+```yaml
+a: cat
+```
+then
+```bash
+yq eval '.a anchor = "foobar"' sample.yml
+```
+will output
+```yaml
+a: &foobar cat
+```
+
+## Get alias
+Given a sample.yml file of:
+```yaml
+b: &billyBob meow
+a: *billyBob
+```
+then
+```bash
+yq eval '.a | alias' sample.yml
+```
+will output
+```yaml
+billyBob
+```
+
+## Set alias
+Given a sample.yml file of:
+```yaml
+b: &meow purr
+a: cat
+```
+then
+```bash
+yq eval '.a alias = "meow"' sample.yml
+```
+will output
+```yaml
+b: &meow purr
+a: *meow
+```
+
 ## Explode alias and anchor
 Given a sample.yml file of:
 ```yaml

pkg/yqlib/doc/headers/Anchor and Aliases Operators.md

@@ -0,0 +1,4 @@
+Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference aliases and remove anchor names).
+
+`yq` supports merge aliases (like `<<: *blah`) however this is no longer in the standard yaml spec (1.2) and so `yq` will automatically add the `!!merge` tag to these nodes as it is effectively a custom tag.
+

pkg/yqlib/doc/headers/Explode.md

@@ -1 +0,0 @@
-Explodes (or dereferences) aliases and anchors.

pkg/yqlib/lib.go

@@ -37,6 +37,7 @@ var AssignStyle = &OperationType{Type: "ASSIGN_STYLE", NumArgs: 2, Precedence: 4
 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 AssignAlias = &OperationType{Type: "ASSIGN_ALIAS", NumArgs: 2, Precedence: 40, Handler: AssignAliasOperator}
 
 var Multiply = &OperationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: MultiplyOperator}
 var Add = &OperationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: AddOperator}
@@ -53,6 +54,7 @@ var GetStyle = &OperationType{Type: "GET_STYLE", NumArgs: 0, Precedence: 50, Han
 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 GetAlias = &OperationType{Type: "GET_ALIAS", NumArgs: 0, Precedence: 50, Handler: GetAliasOperator}
 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

@@ -1,48 +0,0 @@
-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

@@ -1,31 +0,0 @@
-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/operator_anchors_aliases.go

@@ -6,6 +6,88 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+
+	log.Debugf("AssignAlias operator!")
+
+	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+	if err != nil {
+		return nil, err
+	}
+	aliasName := ""
+	if rhs.Front() != nil {
+		aliasName = 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 aliasName : %v", candidate.GetKey())
+		candidate.Node.Kind = yaml.AliasNode
+		candidate.Node.Value = aliasName
+	}
+	return matchingNodes, nil
+}
+
+func GetAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+	log.Debugf("GetAlias operator!")
+	var results = list.New()
+
+	for el := matchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := &yaml.Node{Kind: yaml.ScalarNode, Value: candidate.Node.Value, Tag: "!!str"}
+		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
+		results.PushBack(lengthCand)
+	}
+	return results, nil
+}
+
+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
+}
+
 func ExplodeOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
 	log.Debugf("-- ExplodeOperation")
 

pkg/yqlib/operator_anchors_aliases_test.go

@@ -4,7 +4,39 @@ import (
 	"testing"
 )
 
-var explodeTest = []expressionScenario{
+var anchorOperatorScenarios = []expressionScenario{
+	{
+		description: "Get anchor",
+		document:    `a: &billyBob cat`,
+		expression:  `.a | anchor`,
+		expected: []string{
+			"D0, P[a], (!!str)::billyBob\n",
+		},
+	},
+	{
+		description: "Set anchor",
+		document:    `a: cat`,
+		expression:  `.a anchor = "foobar"`,
+		expected: []string{
+			"D0, P[], (doc)::a: &foobar cat\n",
+		},
+	},
+	{
+		description: "Get alias",
+		document:    `{b: &billyBob meow, a: *billyBob}`,
+		expression:  `.a | alias`,
+		expected: []string{
+			"D0, P[a], (!!str)::billyBob\n",
+		},
+	},
+	{
+		description: "Set alias",
+		document:    `{b: &meow purr, a: cat}`,
+		expression:  `.a alias = "meow"`,
+		expected: []string{
+			"D0, P[], (doc)::{b: &meow purr, a: *meow}\n",
+		},
+	},
 	{
 		description: "Explode alias and anchor",
 		document:    `{f : {a: &a cat, b: *a}}`,
@@ -82,9 +114,9 @@ foobar:
 	},
 }
 
-func TestExplodeOperatorScenarios(t *testing.T) {
-	for _, tt := range explodeTest {
+func TestAnchorAliaseOperatorScenarios(t *testing.T) {
+	for _, tt := range anchorOperatorScenarios {
 		testScenario(t, &tt)
 	}
-	documentScenarios(t, "Explode", explodeTest)
+	documentScenarios(t, "Anchor and Aliases Operators", anchorOperatorScenarios)
 }

pkg/yqlib/path_tokeniser.go

@@ -209,6 +209,7 @@ func initLexer() (*lex.Lexer, error) {
 
 	lexer.Add([]byte(`tag`), opAssignableToken(GetTag, AssignTag))
 	lexer.Add([]byte(`anchor`), opAssignableToken(GetAnchor, AssignAnchor))
+	lexer.Add([]byte(`alias`), opAssignableToken(GetAlias, AssignAlias))
 	lexer.Add([]byte(`filename`), opToken(GetFilename))
 	lexer.Add([]byte(`fileIndex`), opToken(GetFileIndex))
 	lexer.Add([]byte(`path`), opToken(GetPath))