Incrementing version

cmd/version.go

@@ -11,7 +11,7 @@ var (
 	GitDescribe string
 
 	// Version is main version number that is being run at the moment.
-	Version = "4.3.2"
+	Version = "4.4.0"
 
 	// VersionPrerelease is a pre-release marker for the version. If this is "" (empty string)
 	// then it means that it is a final release. Otherwise, this is a pre-release

github-action/Dockerfile

@@ -1,4 +1,4 @@
-FROM mikefarah/yq:4.3.2
+FROM mikefarah/yq:4.4.0
 
 COPY entrypoint.sh /entrypoint.sh
 

pkg/yqlib/doc/Comment Operators.md

@@ -78,17 +78,22 @@ b: dog # leave this
 ```
 
 ## Remove all comments
+Note the use of `...` to ensure key nodes are included.
+
 Given a sample.yml file of:
 ```yaml
 a: cat # comment
+# great
+b: # key comment
 ```
 then
 ```bash
-yq eval '.. comments=""' sample.yml
+yq eval '... comments=""' sample.yml
 ```
 will output
 ```yaml
 a: cat
+b:
 ```
 
 ## Get line comment

pkg/yqlib/doc/Keys.md

@@ -0,0 +1,35 @@
+# Keys
+
+Use the `keys` operator to return map keys or array indices. 
+## Map keys
+Given a sample.yml file of:
+```yaml
+dog: woof
+cat: meow
+```
+then
+```bash
+yq eval 'keys' sample.yml
+```
+will output
+```yaml
+- dog
+- cat
+```
+
+## Array keys
+Given a sample.yml file of:
+```yaml
+- apple
+- banana
+```
+then
+```bash
+yq eval 'keys' sample.yml
+```
+will output
+```yaml
+- 0
+- 1
+```
+

pkg/yqlib/doc/Multiply.md

@@ -111,6 +111,26 @@ b:
   - 5
 ```
 
+## Merge, only existing fields
+Given a sample.yml file of:
+```yaml
+a:
+  thing: one
+  cat: frog
+b:
+  missing: two
+  thing: two
+```
+then
+```bash
+yq eval '.a *? .b' sample.yml
+```
+will output
+```yaml
+thing: two
+cat: frog
+```
+
 ## Merge, appending arrays
 Given a sample.yml file of:
 ```yaml
@@ -143,6 +163,33 @@ array:
 value: banana
 ```
 
+## Merge, only existing fields, appending arrays
+Given a sample.yml file of:
+```yaml
+a:
+  thing:
+    - 1
+    - 2
+b:
+  thing:
+    - 3
+    - 4
+  another:
+    - 1
+```
+then
+```bash
+yq eval '.a *?+ .b' sample.yml
+```
+will output
+```yaml
+thing:
+  - 1
+  - 2
+  - 3
+  - 4
+```
+
 ## Merge to prefix an element
 Given a sample.yml file of:
 ```yaml

pkg/yqlib/doc/Split into Documents.md

@@ -0,0 +1,31 @@
+# Split into Documents
+
+This operator splits all matches into separate documents
+
+## Split empty
+Running
+```bash
+yq eval --null-input 'splitDoc'
+```
+will output
+```yaml
+
+```
+
+## Split array
+Given a sample.yml file of:
+```yaml
+- a: cat
+- b: dog
+```
+then
+```bash
+yq eval '.[] | splitDoc' sample.yml
+```
+will output
+```yaml
+a: cat
+---
+b: dog
+```
+

pkg/yqlib/doc/String Operators.md

@@ -0,0 +1,52 @@
+# String Operators
+
+## Join strings
+Given a sample.yml file of:
+```yaml
+- cat
+- meow
+- 1
+- null
+- true
+```
+then
+```bash
+yq eval 'join("; ")' sample.yml
+```
+will output
+```yaml
+cat; meow; 1; ; true
+```
+
+## Split strings
+Given a sample.yml file of:
+```yaml
+cat; meow; 1; ; true
+```
+then
+```bash
+yq eval 'split("; ")' sample.yml
+```
+will output
+```yaml
+- cat
+- meow
+- "1"
+- ""
+- "true"
+```
+
+## Split strings one match
+Given a sample.yml file of:
+```yaml
+word
+```
+then
+```bash
+yq eval 'split("; ")' sample.yml
+```
+will output
+```yaml
+- word
+```
+

pkg/yqlib/doc/aa.md

@@ -0,0 +1,12 @@
+# Operators
+
+In `yq` expressions are made up of operators. Operators have 0-2 arguments and run against the current 'matching' nodes in the expression tree.
+
+Lets look at a couple of examples.
+
+The `length` operator take no arguments, and will simply return the length of _each_ matching node. So if there were 2 nodes, one string and one array, length will update the 'matching' nodes context to be two new numeric scalar nodes representing the lengths of the orignal 'matching' nodes.
+
+The `=` operator takes two arguments, a `lhs` expression and `rhs` expression. It runs the 'matching' nodes context against the `lhs` expression to find the nodes to update, lets call it `lhsNodes`, and then runs the matching nodes against the `rhs` to find the new values, lets call that `rhsNodes`. It updates the `lhsNodes` values with the `rhsNodes` values and _returns the original matching nodes_. This is important, where length changed the matching nodes to be new nodes with the length values, `=` returns the original matching nodes, albeit with some of the nodes values updated. So `.a = 3` will still return the parent matching node, but with the matching child updated.
+
+Please see the individual operator docs for more information and examples.
+

pkg/yqlib/doc/headers/Keys.md

@@ -0,0 +1,3 @@
+# Keys
+
+Use the `keys` operator to return map keys or array indices. 

pkg/yqlib/doc/headers/Split into Documents.md

@@ -0,0 +1,3 @@
+# Split into Documents
+
+This operator splits all matches into separate documents

pkg/yqlib/doc/headers/String Operators.md

@@ -0,0 +1 @@
+# String Operators

pkg/yqlib/expression_processing_test.go

@@ -53,9 +53,19 @@ var pathTests = []struct {
 		append(make([]interface{}, 0), "3 (int64)", "COLLECT", "SHORT_PIPE"),
 	},
 	{
-		`d0.a`,
-		append(make([]interface{}, 0), "d0", "SHORT_PIPE", "a"),
-		append(make([]interface{}, 0), "d0", "a", "SHORT_PIPE"),
+		`.key.array + .key.array2`,
+		append(make([]interface{}, 0), "key", "SHORT_PIPE", "array", "ADD", "key", "SHORT_PIPE", "array2"),
+		append(make([]interface{}, 0), "key", "array", "SHORT_PIPE", "key", "array2", "SHORT_PIPE", "ADD"),
+	},
+	{
+		`.key.array * .key.array2`,
+		append(make([]interface{}, 0), "key", "SHORT_PIPE", "array", "MULTIPLY", "key", "SHORT_PIPE", "array2"),
+		append(make([]interface{}, 0), "key", "array", "SHORT_PIPE", "key", "array2", "SHORT_PIPE", "MULTIPLY"),
+	},
+	{
+		`.key.array // .key.array2`,
+		append(make([]interface{}, 0), "key", "SHORT_PIPE", "array", "ALTERNATIVE", "key", "SHORT_PIPE", "array2"),
+		append(make([]interface{}, 0), "key", "array", "SHORT_PIPE", "key", "array2", "SHORT_PIPE", "ALTERNATIVE"),
 	},
 	{
 		`.a | .[].b == "apple"`,

pkg/yqlib/expression_tokeniser.go

@@ -3,6 +3,7 @@ package yqlib
 import (
 	"fmt"
 	"strconv"
+	"strings"
 
 	lex "github.com/timtadh/lexmachine"
 	"github.com/timtadh/lexmachine/machines"
@@ -65,21 +66,7 @@ func pathToken(wrapped bool) lex.Action {
 			value = unwrap(value)
 		}
 		log.Debug("PathToken %v", value)
-		op := &Operation{OperationType: traversePathOpType, Value: value, StringValue: value}
-		return &token{TokenType: operationToken, Operation: op, CheckForPostTraverse: true}, nil
-	}
-}
-
-func documentToken() lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-		var numberString = string(m.Bytes)
-		numberString = numberString[1:]
-		var number, errParsingInt = strconv.ParseInt(numberString, 10, 64) // nolint
-		if errParsingInt != nil {
-			return nil, errParsingInt
-		}
-		log.Debug("documentToken %v", string(m.Bytes))
-		op := &Operation{OperationType: documentFilterOpType, Value: number, StringValue: numberString}
+		op := &Operation{OperationType: traversePathOpType, Value: value, StringValue: value, Preferences: traversePreferences{}}
 		return &token{TokenType: operationToken, Operation: op, CheckForPostTraverse: true}, nil
 	}
 }
@@ -101,6 +88,21 @@ func assignOpToken(updateAssign bool) lex.Action {
 	}
 }
 
+func multiplyWithPrefs() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		prefs := multiplyPreferences{}
+		options := string(m.Bytes)
+		if strings.Contains(options, "+") {
+			prefs.AppendArrays = true
+		}
+		if strings.Contains(options, "?") {
+			prefs.TraversePrefs = traversePreferences{DontAutoCreate: true}
+		}
+		op := &Operation{OperationType: multiplyOpType, Value: multiplyOpType.Type, StringValue: options, Preferences: prefs}
+		return &token{TokenType: operationToken, Operation: op}, nil
+	}
+}
+
 func opTokenWithPrefs(op *operationType, assignOpType *operationType, preferences interface{}) lex.Action {
 	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
 		log.Debug("opTokenWithPrefs %v", string(m.Bytes))
@@ -123,7 +125,7 @@ func assignAllCommentsOp(updateAssign bool) lex.Action {
 			Value:         assignCommentOpType.Type,
 			StringValue:   value,
 			UpdateAssign:  updateAssign,
-			Preferences:   &commentOpPreferences{LineComment: true, HeadComment: true, FootComment: true},
+			Preferences:   commentOpPreferences{LineComment: true, HeadComment: true, FootComment: true},
 		}
 		return &token{TokenType: operationToken, Operation: op}, nil
 	}
@@ -181,7 +183,7 @@ func stringValue(wrapped bool) lex.Action {
 func envOp(strenv bool) lex.Action {
 	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
 		value := string(m.Bytes)
-		preferences := &envOpPreferences{}
+		preferences := envOpPreferences{}
 
 		if strenv {
 			// strenv( )
@@ -219,11 +221,11 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`\)`), literalToken(closeBracket, true))
 
 	lexer.Add([]byte(`\.\[`), literalToken(traverseArrayCollect, false))
-	lexer.Add([]byte(`\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, &recursiveDescentPreferences{RecurseArray: true,
-		TraversePreferences: &traversePreferences{FollowAlias: false, IncludeMapKeys: false}}))
+	lexer.Add([]byte(`\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, recursiveDescentPreferences{RecurseArray: true,
+		TraversePreferences: traversePreferences{DontFollowAlias: true, IncludeMapKeys: false}}))
 
-	lexer.Add([]byte(`\.\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, &recursiveDescentPreferences{RecurseArray: true,
-		TraversePreferences: &traversePreferences{FollowAlias: false, IncludeMapKeys: true}}))
+	lexer.Add([]byte(`\.\.\.`), opTokenWithPrefs(recursiveDescentOpType, nil, recursiveDescentPreferences{RecurseArray: true,
+		TraversePreferences: traversePreferences{DontFollowAlias: true, IncludeMapKeys: true}}))
 
 	lexer.Add([]byte(`,`), opToken(unionOpType))
 	lexer.Add([]byte(`:\s*`), opToken(createMapOpType))
@@ -239,6 +241,11 @@ func initLexer() (*lex.Lexer, error) {
 
 	lexer.Add([]byte(`documentIndex`), opToken(getDocumentIndexOpType))
 	lexer.Add([]byte(`di`), opToken(getDocumentIndexOpType))
+	lexer.Add([]byte(`splitDoc`), opToken(splitDocumentOpType))
+
+	lexer.Add([]byte(`join`), opToken(joinStringOpType))
+	lexer.Add([]byte(`split`), opToken(splitStringOpType))
+	lexer.Add([]byte(`keys`), opToken(keysOpType))
 
 	lexer.Add([]byte(`style`), opAssignableToken(getStyleOpType, assignStyleOpType))
 
@@ -250,11 +257,11 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`fi`), opToken(getFileIndexOpType))
 	lexer.Add([]byte(`path`), opToken(getPathOpType))
 
-	lexer.Add([]byte(`lineComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{LineComment: true}))
+	lexer.Add([]byte(`lineComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, commentOpPreferences{LineComment: true}))
 
-	lexer.Add([]byte(`headComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{HeadComment: true}))
+	lexer.Add([]byte(`headComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, commentOpPreferences{HeadComment: true}))
 
-	lexer.Add([]byte(`footComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, &commentOpPreferences{FootComment: true}))
+	lexer.Add([]byte(`footComment`), opTokenWithPrefs(getCommentOpType, assignCommentOpType, commentOpPreferences{FootComment: true}))
 
 	lexer.Add([]byte(`comments\s*=`), assignAllCommentsOp(false))
 	lexer.Add([]byte(`comments\s*\|=`), assignAllCommentsOp(true))
@@ -270,7 +277,6 @@ func initLexer() (*lex.Lexer, error) {
 
 	lexer.Add([]byte("( |\t|\n|\r)+"), skip)
 
-	lexer.Add([]byte(`d[0-9]+`), documentToken())
 	lexer.Add([]byte(`\."[^ "]+"`), pathToken(true))
 	lexer.Add([]byte(`\.[^ \}\{\:\[\],\|\.\[\(\)=]+`), pathToken(false))
 	lexer.Add([]byte(`\.`), selfToken())
@@ -295,8 +301,7 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`\]`), literalToken(closeCollect, true))
 	lexer.Add([]byte(`\{`), literalToken(openCollectObject, false))
 	lexer.Add([]byte(`\}`), literalToken(closeCollectObject, true))
-	lexer.Add([]byte(`\*`), opTokenWithPrefs(multiplyOpType, nil, &multiplyPreferences{AppendArrays: false}))
-	lexer.Add([]byte(`\*\+`), opTokenWithPrefs(multiplyOpType, nil, &multiplyPreferences{AppendArrays: true}))
+	lexer.Add([]byte(`\*[\+|\?]*`), multiplyWithPrefs())
 	lexer.Add([]byte(`\+`), opToken(addOpType))
 	lexer.Add([]byte(`\+=`), opToken(addAssignOpType))
 

pkg/yqlib/lib.go

@@ -40,9 +40,9 @@ var assignCommentOpType = &operationType{Type: "ASSIGN_COMMENT", NumArgs: 2, Pre
 var assignAnchorOpType = &operationType{Type: "ASSIGN_ANCHOR", NumArgs: 2, Precedence: 40, Handler: assignAnchorOperator}
 var assignAliasOpType = &operationType{Type: "ASSIGN_ALIAS", NumArgs: 2, Precedence: 40, Handler: assignAliasOperator}
 
-var multiplyOpType = &operationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: multiplyOperator}
-var addOpType = &operationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: addOperator}
-var alternativeOpType = &operationType{Type: "ALTERNATIVE", NumArgs: 2, Precedence: 45, Handler: alternativeOperator}
+var multiplyOpType = &operationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 42, Handler: multiplyOperator}
+var addOpType = &operationType{Type: "ADD", NumArgs: 2, Precedence: 42, Handler: addOperator}
+var alternativeOpType = &operationType{Type: "ALTERNATIVE", NumArgs: 2, Precedence: 42, Handler: alternativeOperator}
 
 var equalsOpType = &operationType{Type: "EQUALS", NumArgs: 2, Precedence: 40, Handler: equalsOperator}
 var createMapOpType = &operationType{Type: "CREATE_MAP", NumArgs: 2, Precedence: 40, Handler: createMapOperator}
@@ -51,6 +51,7 @@ var shortPipeOpType = &operationType{Type: "SHORT_PIPE", NumArgs: 2, Precedence:
 
 var lengthOpType = &operationType{Type: "LENGTH", NumArgs: 0, Precedence: 50, Handler: lengthOperator}
 var collectOpType = &operationType{Type: "COLLECT", NumArgs: 0, Precedence: 50, Handler: collectOperator}
+var splitDocumentOpType = &operationType{Type: "SPLIT_DOC", NumArgs: 0, Precedence: 50, Handler: splitDocumentOperator}
 var getStyleOpType = &operationType{Type: "GET_STYLE", NumArgs: 0, Precedence: 50, Handler: getStyleOperator}
 var getTagOpType = &operationType{Type: "GET_TAG", NumArgs: 0, Precedence: 50, Handler: getTagOperator}
 var getCommentOpType = &operationType{Type: "GET_COMMENT", NumArgs: 0, Precedence: 50, Handler: getCommentsOperator}
@@ -63,12 +64,15 @@ var getPathOpType = &operationType{Type: "GET_PATH", NumArgs: 0, Precedence: 50,
 
 var explodeOpType = &operationType{Type: "EXPLODE", NumArgs: 1, Precedence: 50, Handler: explodeOperator}
 var sortKeysOpType = &operationType{Type: "SORT_KEYS", NumArgs: 1, Precedence: 50, Handler: sortKeysOperator}
+var joinStringOpType = &operationType{Type: "JOIN", NumArgs: 1, Precedence: 50, Handler: joinStringOperator}
+var splitStringOpType = &operationType{Type: "SPLIT", NumArgs: 1, Precedence: 50, Handler: splitStringOperator}
+
+var keysOpType = &operationType{Type: "KEYS", NumArgs: 0, Precedence: 50, Handler: keysOperator}
 
 var collectObjectOpType = &operationType{Type: "COLLECT_OBJECT", NumArgs: 0, Precedence: 50, Handler: collectObjectOperator}
 var traversePathOpType = &operationType{Type: "TRAVERSE_PATH", NumArgs: 0, Precedence: 50, Handler: traversePathOperator}
 var traverseArrayOpType = &operationType{Type: "TRAVERSE_ARRAY", NumArgs: 1, Precedence: 50, Handler: traverseArrayOperator}
 
-var documentFilterOpType = &operationType{Type: "DOCUMENT_FILTER", NumArgs: 0, Precedence: 50, Handler: traversePathOperator}
 var selfReferenceOpType = &operationType{Type: "SELF", NumArgs: 0, Precedence: 50, Handler: selfOperator}
 var valueOpType = &operationType{Type: "VALUE", NumArgs: 0, Precedence: 50, Handler: valueOperator}
 var envOpType = &operationType{Type: "ENV", NumArgs: 0, Precedence: 50, Handler: envOperator}
@@ -120,8 +124,6 @@ func createValueOperation(value interface{}, stringValue string) *Operation {
 func (p *Operation) toString() string {
 	if p.OperationType == traversePathOpType {
 		return fmt.Sprintf("%v", p.Value)
-	} else if p.OperationType == documentFilterOpType {
-		return fmt.Sprintf("d%v", p.Value)
 	} else if p.OperationType == selfReferenceOpType {
 		return "SELF"
 	} else if p.OperationType == valueOpType {

pkg/yqlib/operator_collect_object.go

@@ -60,7 +60,7 @@ func collect(d *dataTreeNavigator, aggregate *list.List, remainingMatches *list.
 	candidate := remainingMatches.Remove(remainingMatches.Front()).(*CandidateNode)
 
 	splatted, err := splat(d, nodeToMap(candidate),
-		&traversePreferences{FollowAlias: false, IncludeMapKeys: false})
+		traversePreferences{DontFollowAlias: true, IncludeMapKeys: false})
 
 	for splatEl := splatted.Front(); splatEl != nil; splatEl = splatEl.Next() {
 		splatEl.Value.(*CandidateNode).Path = nil
@@ -87,7 +87,7 @@ func collect(d *dataTreeNavigator, aggregate *list.List, remainingMatches *list.
 
 			newCandidate.Path = nil
 
-			newCandidate, err = multiply(&multiplyPreferences{AppendArrays: false})(d, newCandidate, splatCandidate)
+			newCandidate, err = multiply(multiplyPreferences{AppendArrays: false})(d, newCandidate, splatCandidate)
 			if err != nil {
 				return nil, err
 			}

pkg/yqlib/operator_comments.go

@@ -23,7 +23,7 @@ func assignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, expr
 		return nil, err
 	}
 
-	preferences := expressionNode.Operation.Preferences.(*commentOpPreferences)
+	preferences := expressionNode.Operation.Preferences.(commentOpPreferences)
 
 	comment := ""
 	if !expressionNode.Operation.UpdateAssign {
@@ -67,7 +67,7 @@ func assignCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, expr
 }
 
 func getCommentsOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
-	preferences := expressionNode.Operation.Preferences.(*commentOpPreferences)
+	preferences := expressionNode.Operation.Preferences.(commentOpPreferences)
 	log.Debugf("GetComments operator!")
 	var results = list.New()
 

pkg/yqlib/operator_comments_test.go

@@ -71,11 +71,12 @@ var commentOperatorScenarios = []expressionScenario{
 		},
 	},
 	{
-		description: "Remove all comments",
-		document:    "# hi\n\na: cat # comment\n\n# great\n",
-		expression:  `.. comments=""`,
+		description:    "Remove all comments",
+		subdescription: "Note the use of `...` to ensure key nodes are included.",
+		document:       "# hi\n\na: cat # comment\n\n# great\n\nb: # key comment",
+		expression:     `... comments=""`,
 		expected: []string{
-			"D0, P[], (!!map)::a: cat\n",
+			"D0, P[], (!!map)::a: cat\nb:\n",
 		},
 	},
 	{

pkg/yqlib/operator_delete.go

@@ -25,7 +25,7 @@ func deleteChildOperator(d *dataTreeNavigator, matchingNodes *list.List, express
 
 		deleteImmediateChildOpNode := &ExpressionNode{
 			Operation: deleteImmediateChildOp,
-			Rhs:       createTraversalTree(candidate.Path[0 : len(candidate.Path)-1]),
+			Rhs:       createTraversalTree(candidate.Path[0:len(candidate.Path)-1], traversePreferences{}),
 		}
 
 		_, err := d.GetMatchingNodes(matchingNodes, deleteImmediateChildOpNode)

pkg/yqlib/operator_env.go

@@ -19,7 +19,7 @@ func envOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *Expr
 
 	rawValue := os.Getenv(envName)
 
-	preferences := expressionNode.Operation.Preferences.(*envOpPreferences)
+	preferences := expressionNode.Operation.Preferences.(envOpPreferences)
 
 	var node *yaml.Node
 	if preferences.StringValue {

pkg/yqlib/operator_keys.go

@@ -0,0 +1,54 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+
+	"gopkg.in/yaml.v3"
+)
+
+func keysOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	log.Debugf("-- keysOperator")
+
+	var results = list.New()
+
+	for el := matchMap.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := unwrapDoc(candidate.Node)
+		var targetNode *yaml.Node
+		if node.Kind == yaml.MappingNode {
+			targetNode = getMapKeys(node)
+		} else if node.Kind == yaml.SequenceNode {
+			targetNode = getIndicies(node)
+		} else {
+			return nil, fmt.Errorf("Cannot get keys of %v, keys only works for maps and arrays", node.Tag)
+		}
+
+		result := candidate.CreateChild(nil, targetNode)
+		results.PushBack(result)
+	}
+
+	return results, nil
+}
+
+func getMapKeys(node *yaml.Node) *yaml.Node {
+	contents := make([]*yaml.Node, 0)
+	for index := 0; index < len(node.Content); index = index + 2 {
+		contents = append(contents, node.Content[index])
+	}
+	return &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq", Content: contents}
+}
+
+func getIndicies(node *yaml.Node) *yaml.Node {
+	var contents = make([]*yaml.Node, len(node.Content))
+
+	for index := range node.Content {
+		contents[index] = &yaml.Node{
+			Kind:  yaml.ScalarNode,
+			Tag:   "!!int",
+			Value: fmt.Sprintf("%v", index),
+		}
+	}
+
+	return &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq", Content: contents}
+}

pkg/yqlib/operator_keys_test.go

@@ -0,0 +1,47 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var keysOperatorScenarios = []expressionScenario{
+	{
+		description: "Map keys",
+		document:    `{dog: woof, cat: meow}`,
+		expression:  `keys`,
+		expected: []string{
+			"D0, P[], (!!seq)::- dog\n- cat\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `{}`,
+		expression: `keys`,
+		expected: []string{
+			"D0, P[], (!!seq)::[]\n",
+		},
+	},
+	{
+		description: "Array keys",
+		document:    `[apple, banana]`,
+		expression:  `keys`,
+		expected: []string{
+			"D0, P[], (!!seq)::- 0\n- 1\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[]`,
+		expression: `keys`,
+		expected: []string{
+			"D0, P[], (!!seq)::[]\n",
+		},
+	},
+}
+
+func TestKeysOperatorScenarios(t *testing.T) {
+	for _, tt := range keysOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Keys", keysOperatorScenarios)
+}

pkg/yqlib/operator_multiply.go

@@ -44,44 +44,44 @@ func crossFunction(d *dataTreeNavigator, matchingNodes *list.List, expressionNod
 }
 
 type multiplyPreferences struct {
-	AppendArrays bool
+	AppendArrays  bool
+	TraversePrefs traversePreferences
 }
 
 func multiplyOperator(d *dataTreeNavigator, matchingNodes *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	log.Debugf("-- MultiplyOperator")
-	return crossFunction(d, matchingNodes, expressionNode, multiply(expressionNode.Operation.Preferences.(*multiplyPreferences)))
+	return crossFunction(d, matchingNodes, expressionNode, multiply(expressionNode.Operation.Preferences.(multiplyPreferences)))
 }
 
-func multiply(preferences *multiplyPreferences) func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
+func multiply(preferences multiplyPreferences) func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 	return func(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 		lhs.Node = unwrapDoc(lhs.Node)
 		rhs.Node = unwrapDoc(rhs.Node)
 		log.Debugf("Multipling LHS: %v", lhs.Node.Tag)
 		log.Debugf("-          RHS: %v", rhs.Node.Tag)
 
-		shouldAppendArrays := preferences.AppendArrays
-
 		if lhs.Node.Kind == yaml.MappingNode && rhs.Node.Kind == yaml.MappingNode ||
 			(lhs.Node.Kind == yaml.SequenceNode && rhs.Node.Kind == yaml.SequenceNode) {
 
 			var newBlank = lhs.CreateChild(nil, &yaml.Node{})
-			var newThing, err = mergeObjects(d, newBlank, lhs, false)
+			var newThing, err = mergeObjects(d, newBlank, lhs, multiplyPreferences{})
 			if err != nil {
 				return nil, err
 			}
-			return mergeObjects(d, newThing, rhs, shouldAppendArrays)
+			return mergeObjects(d, newThing, rhs, preferences)
 
 		}
 		return nil, fmt.Errorf("Cannot multiply %v with %v", lhs.Node.Tag, rhs.Node.Tag)
 	}
 }
 
-func mergeObjects(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode, shouldAppendArrays bool) (*CandidateNode, error) {
+func mergeObjects(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode, preferences multiplyPreferences) (*CandidateNode, error) {
+	shouldAppendArrays := preferences.AppendArrays
 	var results = list.New()
 
 	// shouldn't recurse arrays if appending
-	prefs := &recursiveDescentPreferences{RecurseArray: !shouldAppendArrays,
-		TraversePreferences: &traversePreferences{FollowAlias: false}}
+	prefs := recursiveDescentPreferences{RecurseArray: !shouldAppendArrays,
+		TraversePreferences: traversePreferences{DontFollowAlias: true}}
 	err := recursiveDecent(d, results, nodeToMap(rhs), prefs)
 	if err != nil {
 		return nil, err
@@ -93,7 +93,7 @@ func mergeObjects(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode,
 	}
 
 	for el := results.Front(); el != nil; el = el.Next() {
-		err := applyAssignment(d, pathIndexToStartFrom, lhs, el.Value.(*CandidateNode), shouldAppendArrays)
+		err := applyAssignment(d, pathIndexToStartFrom, lhs, el.Value.(*CandidateNode), preferences)
 		if err != nil {
 			return nil, err
 		}
@@ -101,8 +101,8 @@ func mergeObjects(d *dataTreeNavigator, lhs *CandidateNode, rhs *CandidateNode,
 	return lhs, nil
 }
 
-func applyAssignment(d *dataTreeNavigator, pathIndexToStartFrom int, lhs *CandidateNode, rhs *CandidateNode, shouldAppendArrays bool) error {
-
+func applyAssignment(d *dataTreeNavigator, pathIndexToStartFrom int, lhs *CandidateNode, rhs *CandidateNode, preferences multiplyPreferences) error {
+	shouldAppendArrays := preferences.AppendArrays
 	log.Debugf("merge - applyAssignment lhs %v, rhs: %v", NodeToString(lhs), NodeToString(rhs))
 
 	lhsPath := rhs.Path[pathIndexToStartFrom:]
@@ -116,7 +116,7 @@ func applyAssignment(d *dataTreeNavigator, pathIndexToStartFrom int, lhs *Candid
 	}
 	rhsOp := &Operation{OperationType: valueOpType, CandidateNode: rhs}
 
-	assignmentOpNode := &ExpressionNode{Operation: assignmentOp, Lhs: createTraversalTree(lhsPath), Rhs: &ExpressionNode{Operation: rhsOp}}
+	assignmentOpNode := &ExpressionNode{Operation: assignmentOp, Lhs: createTraversalTree(lhsPath, preferences.TraversePrefs), Rhs: &ExpressionNode{Operation: rhsOp}}
 
 	_, err := d.GetMatchingNodes(nodeToMap(lhs), assignmentOpNode)
 

pkg/yqlib/operator_multiply_test.go

@@ -107,6 +107,22 @@ b:
 			"D0, P[a], (!!seq)::[1, 2]\n",
 		},
 	},
+	{
+		description: "Merge, only existing fields",
+		document:    `{a: {thing: one, cat: frog}, b: {missing: two, thing: two}}`,
+		expression:  `.a *? .b`,
+		expected: []string{
+			"D0, P[a], (!!map)::{thing: two, cat: frog}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `{a: [{thing: one}], b: [{missing: two, thing: two}]}`,
+		expression: `.a *? .b`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[{thing: two}]\n",
+		},
+	},
 	{
 		description: "Merge, appending arrays",
 		document:    `{a: {array: [1, 2, animal: dog], value: coconut}, b: {array: [3, 4, animal: cat], value: banana}}`,
@@ -115,6 +131,14 @@ b:
 			"D0, P[a], (!!map)::{array: [1, 2, {animal: dog}, 3, 4, {animal: cat}], value: banana}\n",
 		},
 	},
+	{
+		description: "Merge, only existing fields, appending arrays",
+		document:    `{a: {thing: [1,2]}, b: {thing: [3,4], another: [1]}}`,
+		expression:  `.a *?+ .b`,
+		expected: []string{
+			"D0, P[a], (!!map)::{thing: [1, 2, 3, 4]}\n",
+		},
+	},
 	{
 		description: "Merge to prefix an element",
 		document:    `{a: cat, b: dog}`,

pkg/yqlib/operator_recursive_descent.go

@@ -7,14 +7,14 @@ import (
 )
 
 type recursiveDescentPreferences struct {
-	TraversePreferences *traversePreferences
+	TraversePreferences traversePreferences
 	RecurseArray        bool
 }
 
 func recursiveDescentOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
 	var results = list.New()
 
-	preferences := expressionNode.Operation.Preferences.(*recursiveDescentPreferences)
+	preferences := expressionNode.Operation.Preferences.(recursiveDescentPreferences)
 	err := recursiveDecent(d, results, matchMap, preferences)
 	if err != nil {
 		return nil, err
@@ -23,7 +23,7 @@ func recursiveDescentOperator(d *dataTreeNavigator, matchMap *list.List, express
 	return results, nil
 }
 
-func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.List, preferences *recursiveDescentPreferences) error {
+func recursiveDecent(d *dataTreeNavigator, results *list.List, matchMap *list.List, preferences recursiveDescentPreferences) error {
 	for el := matchMap.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 

pkg/yqlib/operator_split_document.go

@@ -0,0 +1,18 @@
+package yqlib
+
+import (
+	"container/list"
+)
+
+func splitDocumentOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	log.Debugf("-- splitDocumentOperator")
+
+	var index uint = 0
+	for el := matchMap.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		candidate.Document = index
+		index = index + 1
+	}
+
+	return matchMap, nil
+}

pkg/yqlib/operator_split_document_test.go

@@ -0,0 +1,32 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var splitDocOperatorScenarios = []expressionScenario{
+	{
+		description: "Split empty",
+		document:    ``,
+		expression:  `splitDoc`,
+		expected: []string{
+			"D0, P[], (!!null)::\n",
+		},
+	},
+	{
+		description: "Split array",
+		document:    `[{a: cat}, {b: dog}]`,
+		expression:  `.[] | splitDoc`,
+		expected: []string{
+			"D0, P[0], (!!map)::{a: cat}\n",
+			"D1, P[1], (!!map)::{b: dog}\n",
+		},
+	},
+}
+
+func TestSplitDocOperatorScenarios(t *testing.T) {
+	for _, tt := range splitDocOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Split into Documents", splitDocOperatorScenarios)
+}

pkg/yqlib/operator_strings.go

@@ -0,0 +1,96 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+)
+
+func joinStringOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	log.Debugf("-- joinStringOperator")
+	joinStr := ""
+
+	rhs, err := d.GetMatchingNodes(matchMap, expressionNode.Rhs)
+	if err != nil {
+		return nil, err
+	}
+	if rhs.Front() != nil {
+		joinStr = rhs.Front().Value.(*CandidateNode).Node.Value
+	}
+
+	var results = list.New()
+
+	for el := matchMap.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := unwrapDoc(candidate.Node)
+		if node.Kind != yaml.SequenceNode {
+			return nil, fmt.Errorf("Cannot join with %v, can only join arrays of scalars", node.Tag)
+		}
+		targetNode := join(node.Content, joinStr)
+		result := candidate.CreateChild(nil, targetNode)
+		results.PushBack(result)
+	}
+
+	return results, nil
+}
+
+func join(content []*yaml.Node, joinStr string) *yaml.Node {
+	var stringsToJoin []string
+	for _, node := range content {
+		str := node.Value
+		if node.Tag == "!!null" {
+			str = ""
+		}
+		stringsToJoin = append(stringsToJoin, str)
+	}
+
+	return &yaml.Node{Kind: yaml.ScalarNode, Value: strings.Join(stringsToJoin, joinStr), Tag: "!!str"}
+}
+
+func splitStringOperator(d *dataTreeNavigator, matchMap *list.List, expressionNode *ExpressionNode) (*list.List, error) {
+	log.Debugf("-- splitStringOperator")
+	splitStr := ""
+
+	rhs, err := d.GetMatchingNodes(matchMap, expressionNode.Rhs)
+	if err != nil {
+		return nil, err
+	}
+	if rhs.Front() != nil {
+		splitStr = rhs.Front().Value.(*CandidateNode).Node.Value
+	}
+
+	var results = list.New()
+
+	for el := matchMap.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := unwrapDoc(candidate.Node)
+		if node.Tag == "!!null" {
+			continue
+		}
+		if node.Tag != "!!str" {
+			return nil, fmt.Errorf("Cannot split %v, can only split strings", node.Tag)
+		}
+		targetNode := split(node.Value, splitStr)
+		result := candidate.CreateChild(nil, targetNode)
+		results.PushBack(result)
+	}
+
+	return results, nil
+}
+
+func split(value string, spltStr string) *yaml.Node {
+	var contents []*yaml.Node
+
+	if value != "" {
+		var newStrings = strings.Split(value, spltStr)
+		contents = make([]*yaml.Node, len(newStrings))
+
+		for index, str := range newStrings {
+			contents[index] = &yaml.Node{Kind: yaml.ScalarNode, Tag: "!!str", Value: str}
+		}
+	}
+
+	return &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq", Content: contents}
+}

pkg/yqlib/operator_strings_test.go

@@ -0,0 +1,52 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var stringsOperatorScenarios = []expressionScenario{
+	{
+		description: "Join strings",
+		document:    `[cat, meow, 1, null, true]`,
+		expression:  `join("; ")`,
+		expected: []string{
+			"D0, P[], (!!str)::cat; meow; 1; ; true\n",
+		},
+	},
+	{
+		description: "Split strings",
+		document:    `"cat; meow; 1; ; true"`,
+		expression:  `split("; ")`,
+		expected: []string{
+			"D0, P[], (!!seq)::- cat\n- meow\n- \"1\"\n- \"\"\n- \"true\"\n",
+		},
+	},
+	{
+		description: "Split strings one match",
+		document:    `"word"`,
+		expression:  `split("; ")`,
+		expected: []string{
+			"D0, P[], (!!seq)::- word\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `""`,
+		expression: `split("; ")`,
+		expected: []string{
+			"D0, P[], (!!seq)::[]\n", // dont actually want this, just not to error
+		},
+	},
+	{
+		skipDoc:    true,
+		expression: `split("; ")`,
+		expected:   []string{},
+	},
+}
+
+func TestStringsOperatorScenarios(t *testing.T) {
+	for _, tt := range stringsOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "String Operators", stringsOperatorScenarios)
+}

pkg/yqlib/operator_traverse_path.go

@@ -10,11 +10,12 @@ import (
 )
 
 type traversePreferences struct {
-	FollowAlias    bool
-	IncludeMapKeys bool
+	DontFollowAlias bool
+	IncludeMapKeys  bool
+	DontAutoCreate  bool // by default, we automatically create entries on the fly.
 }
 
-func splat(d *dataTreeNavigator, matches *list.List, prefs *traversePreferences) (*list.List, error) {
+func splat(d *dataTreeNavigator, matches *list.List, prefs traversePreferences) (*list.List, error) {
 	return traverseNodesWithArrayIndices(matches, make([]*yaml.Node, 0), prefs)
 }
 
@@ -54,8 +55,7 @@ func traverse(d *dataTreeNavigator, matchingNode *CandidateNode, operation *Oper
 	switch value.Kind {
 	case yaml.MappingNode:
 		log.Debug("its a map with %v entries", len(value.Content)/2)
-		prefs := &traversePreferences{FollowAlias: true}
-		return traverseMap(matchingNode, operation.StringValue, prefs, false)
+		return traverseMap(matchingNode, operation.StringValue, operation.Preferences.(traversePreferences), false)
 
 	case yaml.SequenceNode:
 		log.Debug("its a sequence of %v things!", len(value.Content))
@@ -83,11 +83,10 @@ func traverseArrayOperator(d *dataTreeNavigator, matchingNodes *list.List, expre
 	}
 
 	var indicesToTraverse = rhs.Front().Value.(*CandidateNode).Node.Content
-	prefs := &traversePreferences{FollowAlias: true}
-	return traverseNodesWithArrayIndices(matchingNodes, indicesToTraverse, prefs)
+	return traverseNodesWithArrayIndices(matchingNodes, indicesToTraverse, traversePreferences{})
 }
 
-func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse []*yaml.Node, prefs *traversePreferences) (*list.List, error) {
+func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse []*yaml.Node, prefs traversePreferences) (*list.List, error) {
 	var matchingNodeMap = list.New()
 	for el := matchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
@@ -101,7 +100,7 @@ func traverseNodesWithArrayIndices(matchingNodes *list.List, indicesToTraverse [
 	return matchingNodeMap, nil
 }
 
-func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml.Node, prefs *traversePreferences) (*list.List, error) { // call this if doc / alias like the other traverse
+func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml.Node, prefs traversePreferences) (*list.List, error) { // call this if doc / alias like the other traverse
 	node := matchingNode.Node
 	if node.Tag == "!!null" {
 		log.Debugf("OperatorArrayTraverse got a null - turning it into an empty array")
@@ -124,7 +123,7 @@ func traverseArrayIndices(matchingNode *CandidateNode, indicesToTraverse []*yaml
 	return list.New(), nil
 }
 
-func traverseMapWithIndices(candidate *CandidateNode, indices []*yaml.Node, prefs *traversePreferences) (*list.List, error) {
+func traverseMapWithIndices(candidate *CandidateNode, indices []*yaml.Node, prefs traversePreferences) (*list.List, error) {
 	if len(indices) == 0 {
 		return traverseMap(candidate, "", prefs, true)
 	}
@@ -188,7 +187,7 @@ func keyMatches(key *yaml.Node, wantedKey string) bool {
 	return matchKey(key.Value, wantedKey)
 }
 
-func traverseMap(matchingNode *CandidateNode, key string, prefs *traversePreferences, splat bool) (*list.List, error) {
+func traverseMap(matchingNode *CandidateNode, key string, prefs traversePreferences, splat bool) (*list.List, error) {
 	var newMatches = orderedmap.NewOrderedMap()
 	err := doTraverseMap(newMatches, matchingNode, key, prefs, splat)
 
@@ -196,7 +195,7 @@ func traverseMap(matchingNode *CandidateNode, key string, prefs *traversePrefere
 		return nil, err
 	}
 
-	if newMatches.Len() == 0 {
+	if !prefs.DontAutoCreate && newMatches.Len() == 0 {
 		//no matches, create one automagically
 		valueNode := &yaml.Node{Tag: "!!null", Kind: yaml.ScalarNode, Value: "null"}
 		node := matchingNode.Node
@@ -214,7 +213,7 @@ func traverseMap(matchingNode *CandidateNode, key string, prefs *traversePrefere
 	return results, nil
 }
 
-func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode, wantedKey string, prefs *traversePreferences, splat bool) error {
+func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode, wantedKey string, prefs traversePreferences, splat bool) error {
 	// value.Content is a concatenated array of key, value,
 	// so keys are in the even indexes, values in odd.
 	// merge aliases are defined first, but we only want to traverse them
@@ -229,7 +228,7 @@ func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode,
 
 		log.Debug("checking %v (%v)", key.Value, key.Tag)
 		//skip the 'merge' tag, find a direct match first
-		if key.Tag == "!!merge" && prefs.FollowAlias {
+		if key.Tag == "!!merge" && !prefs.DontFollowAlias {
 			log.Debug("Merge anchor")
 			err := traverseMergeAnchor(newMatches, candidate, value, wantedKey, prefs, splat)
 			if err != nil {
@@ -249,7 +248,7 @@ func doTraverseMap(newMatches *orderedmap.OrderedMap, candidate *CandidateNode,
 	return nil
 }
 
-func traverseMergeAnchor(newMatches *orderedmap.OrderedMap, originalCandidate *CandidateNode, value *yaml.Node, wantedKey string, prefs *traversePreferences, splat bool) error {
+func traverseMergeAnchor(newMatches *orderedmap.OrderedMap, originalCandidate *CandidateNode, value *yaml.Node, wantedKey string, prefs traversePreferences, splat bool) error {
 	switch value.Kind {
 	case yaml.AliasNode:
 		candidateNode := originalCandidate.CreateChild(nil, value.Alias)

pkg/yqlib/operators.go

@@ -35,14 +35,16 @@ func nodeToMap(candidate *CandidateNode) *list.List {
 	return elMap
 }
 
-func createTraversalTree(path []interface{}) *ExpressionNode {
+func createTraversalTree(path []interface{}, traversePrefs traversePreferences) *ExpressionNode {
 	if len(path) == 0 {
 		return &ExpressionNode{Operation: &Operation{OperationType: selfReferenceOpType}}
 	} else if len(path) == 1 {
-		return &ExpressionNode{Operation: &Operation{OperationType: traversePathOpType, Value: path[0], StringValue: fmt.Sprintf("%v", path[0])}}
+		return &ExpressionNode{Operation: &Operation{OperationType: traversePathOpType, Preferences: traversePrefs, Value: path[0], StringValue: fmt.Sprintf("%v", path[0])}}
 	}
+
 	return &ExpressionNode{
 		Operation: &Operation{OperationType: shortPipeOpType},
-		Lhs:       createTraversalTree(path[0:1]),
-		Rhs:       createTraversalTree(path[1:])}
+		Lhs:       createTraversalTree(path[0:1], traversePrefs),
+		Rhs:       createTraversalTree(path[1:], traversePrefs),
+	}
 }

pkg/yqlib/operators_test.go

@@ -55,7 +55,7 @@ func testScenario(t *testing.T, s *expressionScenario) {
 		candidateNode := &CandidateNode{
 			Document:  0,
 			Filename:  "",
-			Node:      &yaml.Node{Tag: "!!null"},
+			Node:      &yaml.Node{Tag: "!!null", Kind: yaml.ScalarNode},
 			FileIndex: 0,
 		}
 		inputs.PushBack(candidateNode)
@@ -245,7 +245,7 @@ func documentOutput(t *testing.T, w *bufio.Writer, s expressionScenario, formatt
 		candidateNode := &CandidateNode{
 			Document:  0,
 			Filename:  "",
-			Node:      &yaml.Node{Tag: "!!null"},
+			Node:      &yaml.Node{Tag: "!!null", Kind: yaml.ScalarNode},
 			FileIndex: 0,
 		}
 		inputs.PushBack(candidateNode)

pkg/yqlib/stream_evaluator.go

@@ -35,7 +35,7 @@ func (s *streamEvaluator) EvaluateNew(expression string, printer Printer) error
 	candidateNode := &CandidateNode{
 		Document:  0,
 		Filename:  "",
-		Node:      &yaml.Node{Tag: "!!null"},
+		Node:      &yaml.Node{Tag: "!!null", Kind: yaml.ScalarNode},
 		FileIndex: 0,
 	}
 	inputList := list.New()

snap/snapcraft.yaml

@@ -1,5 +1,5 @@
 name: yq
-version: '4.3.2'
+version: '4.4.0'
 summary: A lightweight and portable command-line YAML processor
 description: |
   The aim of the project is to be the jq or sed of yaml files.