Increment version

cmd/evaluate_all_command.go

@@ -17,6 +17,9 @@ func createEvaluateAllCommand() *cobra.Command {
 		Example: `
 # merges f2.yml into f1.yml (inplace)
 yq eval-all --inplace 'select(fileIndex == 0) * select(fileIndex == 1)' f1.yml f2.yml		
+
+# use '-' as a filename to read from STDIN
+cat file2.yml | yq ea '.a.b' file1.yml - file3.yml
 `,
 		Long: "Evaluate All:\nUseful when you need to run an expression across several yaml documents or files. Consumes more memory than eval",
 		RunE: evaluateAll,

cmd/evalute_sequence_command.go

@@ -21,6 +21,9 @@ yq e '.a.b | length' f1.yml f2.yml
 # prints out the file
 yq e sample.yaml 
 
+# use '-' as a filename to read from STDIN
+cat file2.yml | yq e '.a.b' file1.yml - file3.yml
+
 # prints a new yaml document
 yq e -n '.a.b.c = "cat"' 
 

cmd/version.go

@@ -11,7 +11,7 @@ var (
 	GitDescribe string
 
 	// Version is main version number that is being run at the moment.
-	Version = "4.6.3"
+	Version = "4.7.1"
 
 	// 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:4.6.3
+FROM mikefarah/yq:4.7.1
 
 COPY entrypoint.sh /entrypoint.sh
 

pkg/yqlib/candidate_node.go

@@ -8,9 +8,10 @@ import (
 )
 
 type CandidateNode struct {
-	Node      *yaml.Node    // the actual node
-	Path      []interface{} /// the path we took to get to this node
-	Document  uint          // the document index of this node
+	Node      *yaml.Node     // the actual node
+	Parent    *CandidateNode // parent node
+	Path      []interface{}  /// the path we took to get to this node
+	Document  uint           // the document index of this node
 	Filename  string
 	FileIndex int
 	// when performing op against all nodes given, this will treat all the nodes as one
@@ -31,6 +32,7 @@ func (n *CandidateNode) CreateChild(path interface{}, node *yaml.Node) *Candidat
 	return &CandidateNode{
 		Node:      node,
 		Path:      n.createChildPath(path),
+		Parent:    n,
 		Document:  n.Document,
 		Filename:  n.Filename,
 		FileIndex: n.FileIndex,

pkg/yqlib/doc/Anchor and Alias Operators.md

@@ -1,4 +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).
+Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference (or expands) 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/String Operators.md

@@ -18,6 +18,42 @@ will output
 cat; meow; 1; ; true
 ```
 
+## Substitute / Replace string
+This uses golang regex, described [here](https://github.com/google/re2/wiki/Syntax)
+Note the use of `|=` to run in context of the current string value.
+
+Given a sample.yml file of:
+```yaml
+a: dogs are great
+```
+then
+```bash
+yq eval '.a |= sub("dogs", "cats")' sample.yml
+```
+will output
+```yaml
+a: cats are great
+```
+
+## Substitute / Replace string with regex
+This uses golang regex, described [here](https://github.com/google/re2/wiki/Syntax)
+Note the use of `|=` to run in context of the current string value.
+
+Given a sample.yml file of:
+```yaml
+a: cat
+b: heat
+```
+then
+```bash
+yq eval '.[] |= sub("(a)", "${1}r")' sample.yml
+```
+will output
+```yaml
+a: cart
+b: heart
+```
+
 ## Split strings
 Given a sample.yml file of:
 ```yaml

pkg/yqlib/doc/aa.md

@@ -1,10 +1,44 @@
 # 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.
+In `yq` expressions are made up of operators and pipes. A context of nodes is passed through the expression and each operation takes the context as input and returns a new context as output. That output is piped in as input for the next operation in the expression. To begin with, the context is set to the first yaml document of the first yaml file (if processing in sequence using eval).
 
 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.
+## Example 1 - simple example
+
+Given a document like:
+
+```yaml
+- [a]
+- "cat"
+```
+
+with an expression:
+
+```
+.[] | length
+```
+
+`yq` will initially set the context as single node of the entire yaml document, an array of two elements.
+
+```yaml
+- [a]
+- "cat"
+```
+
+This gets piped into the splat operator `.[]` which will split out the context into a collection of two nodes `[a]` and `"cat"`. Note that this is _not_ a yaml array.
+
+The `length` operator take no arguments, and will simply return the length of _each_ matching node in the context. So for the context of `[a]` and `"cat"`, it will return a new context of `1` and `3`.
+
+This being the last operation in the expression, the results will be printed out:
+
+```
+1
+3
+```
+
+# Example 2 - operators with arguments.
+
 
 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.
 

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

@@ -1,4 +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).
+Use the `alias` and `anchor` operators to read and write yaml aliases and anchors. The `explode` operator normalises a yaml file (dereference (or expands) 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/expression_tokeniser.go

@@ -264,6 +264,8 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`splitDoc`), opToken(splitDocumentOpType))
 
 	lexer.Add([]byte(`join`), opToken(joinStringOpType))
+	lexer.Add([]byte(`sub`), opToken(subStringOpType))
+
 	lexer.Add([]byte(`split`), opToken(splitStringOpType))
 	lexer.Add([]byte(`keys`), opToken(keysOpType))
 

pkg/yqlib/lib.go

@@ -75,6 +75,7 @@ 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 subStringOpType = &operationType{Type: "SUBSTR", NumArgs: 1, Precedence: 50, Handler: substituteStringOperator}
 var splitStringOpType = &operationType{Type: "SPLIT", NumArgs: 1, Precedence: 50, Handler: splitStringOperator}
 
 var keysOpType = &operationType{Type: "KEYS", NumArgs: 0, Precedence: 50, Handler: keysOperator}
@@ -94,7 +95,6 @@ var recursiveDescentOpType = &operationType{Type: "RECURSIVE_DESCENT", NumArgs:
 var selectOpType = &operationType{Type: "SELECT", NumArgs: 1, Precedence: 50, Handler: selectOperator}
 var hasOpType = &operationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler: hasOperator}
 var deleteChildOpType = &operationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: deleteChildOperator}
-var deleteImmediateChildOpType = &operationType{Type: "DELETE_IMMEDIATE_CHILD", NumArgs: 1, Precedence: 40, Handler: deleteImmediateChildOperator}
 
 type Operation struct {
 	OperationType *operationType

pkg/yqlib/operator_add.go

@@ -39,7 +39,7 @@ func toNodes(candidate *CandidateNode) []*yaml.Node {
 func addOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("Add operator")
 
-	return crossFunction(d, context, expressionNode, add)
+	return crossFunction(d, context, expressionNode, add, false)
 }
 
 func add(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {

pkg/yqlib/operator_alternative.go

@@ -1,14 +1,14 @@
 package yqlib
 
-// corssFunction no matches
-// can boolean use crossfunction
-
 func alternativeOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- alternative")
-	return crossFunction(d, context, expressionNode, alternativeFunc)
+	return crossFunction(d, context, expressionNode, alternativeFunc, true)
 }
 
 func alternativeFunc(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
+	if lhs == nil {
+		return rhs, nil
+	}
 	lhs.Node = unwrapDoc(lhs.Node)
 	rhs.Node = unwrapDoc(rhs.Node)
 	log.Debugf("Alternative LHS: %v", lhs.Node.Tag)

pkg/yqlib/operator_alternative_test.go

@@ -13,6 +13,14 @@ var alternativeOperatorScenarios = []expressionScenario{
 			"D0, P[a], (!!str)::bridge\n",
 		},
 	},
+	{
+		expression: `select(tag == "seq") // "cat"`,
+		skipDoc:    true,
+		document:   `a: frog`,
+		expected: []string{
+			"D0, P[], (!!str)::cat\n",
+		},
+	},
 	{
 		description: "LHS is not defined",
 		expression:  `.a // "hello"`,

pkg/yqlib/operator_booleans.go

@@ -49,7 +49,7 @@ func orOperator(d *dataTreeNavigator, context Context, expressionNode *Expressio
 	return crossFunction(d, context, expressionNode, performBoolOp(
 		func(b1 bool, b2 bool) bool {
 			return b1 || b2
-		}))
+		}), false)
 }
 
 func andOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
@@ -57,7 +57,7 @@ func andOperator(d *dataTreeNavigator, context Context, expressionNode *Expressi
 	return crossFunction(d, context, expressionNode, performBoolOp(
 		func(b1 bool, b2 bool) bool {
 			return b1 && b2
-		}))
+		}), false)
 }
 
 func notOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {

pkg/yqlib/operator_create_map.go

@@ -62,7 +62,7 @@ func sequenceFor(d *dataTreeNavigator, context Context, matchingNode *CandidateN
 			}
 
 			return &CandidateNode{Node: &node, Document: document, Path: path}, nil
-		})
+		}, false)
 
 	if err != nil {
 		return nil, err

pkg/yqlib/operator_delete.go

@@ -18,48 +18,23 @@ func deleteChildOperator(d *dataTreeNavigator, context Context, expressionNode *
 	for el := nodesToDelete.MatchingNodes.Back(); el != nil; el = el.Prev() {
 		candidate := el.Value.(*CandidateNode)
 
-		if len(candidate.Path) > 0 {
-			deleteImmediateChildOp := &Operation{
-				OperationType: deleteImmediateChildOpType,
-				Value:         candidate.Path[len(candidate.Path)-1],
-			}
-
-			deleteImmediateChildOpNode := &ExpressionNode{
-				Operation: deleteImmediateChildOp,
-				Rhs:       createTraversalTree(candidate.Path[0:len(candidate.Path)-1], traversePreferences{}, false),
-			}
-
-			_, err := d.GetMatchingNodes(contextToUse, deleteImmediateChildOpNode)
-			if err != nil {
-				return Context{}, err
-			}
+		//problem: context may already be '.a' and then I pass in '.a.a2'.
+		// should pass in .a2.
+		if candidate.Parent == nil {
+			log.Info("Could not find parent of %v", candidate.GetKey())
+			return context, nil
 		}
-	}
-	return context, nil
-}
 
-func deleteImmediateChildOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
-	parents, err := d.GetMatchingNodes(context, expressionNode.Rhs)
+		parentNode := candidate.Parent.Node
+		childPath := candidate.Path[len(candidate.Path)-1]
 
-	if err != nil {
-		return Context{}, err
-	}
-
-	childPath := expressionNode.Operation.Value
-
-	log.Debug("childPath to remove %v", childPath)
-
-	for el := parents.MatchingNodes.Front(); el != nil; el = el.Next() {
-		parent := el.Value.(*CandidateNode)
-		parentNode := unwrapDoc(parent.Node)
 		if parentNode.Kind == yaml.MappingNode {
-			deleteFromMap(parent, childPath)
+			deleteFromMap(candidate.Parent, childPath)
 		} else if parentNode.Kind == yaml.SequenceNode {
-			deleteFromArray(parent, childPath)
+			deleteFromArray(candidate.Parent, childPath)
 		} else {
 			return Context{}, fmt.Errorf("Cannot delete nodes from parent of tag %v", parentNode.Tag)
 		}
-
 	}
 	return context, nil
 }

pkg/yqlib/operator_delete_test.go

@@ -21,6 +21,70 @@ var deleteOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{a: {a2: frood}}\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		document:   `{a: {a1: fred, a2: frood}}`,
+		expression: `.a | del(.a1)`,
+		expected: []string{
+			"D0, P[a], (!!map)::{a2: frood}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `a: [1,2,3]`,
+		expression: `.a | del(.[1])`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[1, 3]\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[0, {a: cat, b: dog}]`,
+		expression: `.[1] | del(.a)`,
+		expected: []string{
+			"D0, P[1], (!!map)::{b: dog}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[{a: cat, b: dog}]`,
+		expression: `.[0] | del(.a)`,
+		expected: []string{
+			"D0, P[0], (!!map)::{b: dog}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[{a: {b: thing, c: frog}}]`,
+		expression: `.[0].a | del(.b)`,
+		expected: []string{
+			"D0, P[0 a], (!!map)::{c: frog}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `[{a: {b: thing, c: frog}}]`,
+		expression: `.[0] | del(.a.b)`,
+		expected: []string{
+			"D0, P[0], (!!map)::{a: {c: frog}}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `{a: [0, {b: thing, c: frog}]}`,
+		expression: `.a[1] | del(.b)`,
+		expected: []string{
+			"D0, P[a 1], (!!map)::{c: frog}\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `{a: [0, {b: thing, c: frog}]}`,
+		expression: `.a | del(.[1].b)`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[0, {c: frog}]\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		document:   `{a: {a1: fred, a2: frood}}`,

pkg/yqlib/operator_equals.go

@@ -4,7 +4,7 @@ import "gopkg.in/yaml.v3"
 
 func equalsOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- equalsOperation")
-	return crossFunction(d, context, expressionNode, isEquals(false))
+	return crossFunction(d, context, expressionNode, isEquals(false), false)
 }
 
 func isEquals(flip bool) func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
@@ -29,5 +29,5 @@ func isEquals(flip bool) func(d *dataTreeNavigator, context Context, lhs *Candid
 
 func notEqualsOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- equalsOperation")
-	return crossFunction(d, context, expressionNode, isEquals(true))
+	return crossFunction(d, context, expressionNode, isEquals(true), false)
 }

pkg/yqlib/operator_multiply.go

@@ -17,7 +17,7 @@ type multiplyPreferences struct {
 
 func multiplyOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- MultiplyOperator")
-	return crossFunction(d, context, expressionNode, multiply(expressionNode.Operation.Preferences.(multiplyPreferences)))
+	return crossFunction(d, context, expressionNode, multiply(expressionNode.Operation.Preferences.(multiplyPreferences)), false)
 }
 
 func multiply(preferences multiplyPreferences) func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {

pkg/yqlib/operator_multiply_test.go

@@ -283,5 +283,5 @@ func TestMultiplyOperatorScenarios(t *testing.T) {
 	for _, tt := range multiplyOperatorScenarios {
 		testScenario(t, &tt)
 	}
-	documentScenarios(t, "Multiply", multiplyOperatorScenarios)
+	documentScenarios(t, "Multiply (Merge)", multiplyOperatorScenarios)
 }

pkg/yqlib/operator_strings.go

@@ -3,11 +3,77 @@ package yqlib
 import (
 	"container/list"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"gopkg.in/yaml.v3"
 )
 
+func getSubstituteParameters(d *dataTreeNavigator, block *ExpressionNode, context Context) (string, string, error) {
+	regEx := ""
+	replacementText := ""
+
+	regExNodes, err := d.GetMatchingNodes(context, block.Lhs)
+	if err != nil {
+		return "", "", err
+	}
+	if regExNodes.MatchingNodes.Front() != nil {
+		regEx = regExNodes.MatchingNodes.Front().Value.(*CandidateNode).Node.Value
+	}
+
+	log.Debug("regEx %v", regEx)
+
+	replacementNodes, err := d.GetMatchingNodes(context, block.Rhs)
+	if err != nil {
+		return "", "", err
+	}
+	if replacementNodes.MatchingNodes.Front() != nil {
+		replacementText = replacementNodes.MatchingNodes.Front().Value.(*CandidateNode).Node.Value
+	}
+
+	return regEx, replacementText, nil
+}
+
+func substitute(original string, regex *regexp.Regexp, replacement string) *yaml.Node {
+	replacedString := regex.ReplaceAllString(original, replacement)
+	return &yaml.Node{Kind: yaml.ScalarNode, Value: replacedString, Tag: "!!str"}
+}
+
+func substituteStringOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+	//rhs  block operator
+	//lhs of block = regex
+	//rhs of block = replacement expression
+	block := expressionNode.Rhs
+
+	regExStr, replacementText, err := getSubstituteParameters(d, block, context)
+
+	if err != nil {
+		return Context{}, err
+	}
+
+	regEx, err := regexp.Compile(regExStr)
+	if err != nil {
+		return Context{}, err
+	}
+
+	var results = list.New()
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := unwrapDoc(candidate.Node)
+		if node.Tag != "!!str" {
+			return Context{}, fmt.Errorf("cannot substitute with %v, can only substitute strings. Hint: Most often you'll want to use '|=' over '=' for this operation.", node.Tag)
+		}
+
+		targetNode := substitute(node.Value, regEx, replacementText)
+		result := candidate.CreateChild(nil, targetNode)
+		results.PushBack(result)
+	}
+
+	return context.ChildContext(results), nil
+
+}
+
 func joinStringOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- joinStringOperator")
 	joinStr := ""
@@ -26,7 +92,7 @@ func joinStringOperator(d *dataTreeNavigator, context Context, expressionNode *E
 		candidate := el.Value.(*CandidateNode)
 		node := unwrapDoc(candidate.Node)
 		if node.Kind != yaml.SequenceNode {
-			return Context{}, fmt.Errorf("Cannot join with %v, can only join arrays of scalars", node.Tag)
+			return Context{}, fmt.Errorf("cannot join with %v, can only join arrays of scalars", node.Tag)
 		}
 		targetNode := join(node.Content, joinStr)
 		result := candidate.CreateChild(nil, targetNode)

pkg/yqlib/operator_strings_test.go

@@ -13,6 +13,24 @@ var stringsOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!str)::cat; meow; 1; ; true\n",
 		},
 	},
+	{
+		description:    "Substitute / Replace string",
+		subdescription: "This uses golang regex, described [here](https://github.com/google/re2/wiki/Syntax)\nNote the use of `|=` to run in context of the current string value.",
+		document:       `a: dogs are great`,
+		expression:     `.a |= sub("dogs", "cats")`,
+		expected: []string{
+			"D0, P[], (doc)::a: cats are great\n",
+		},
+	},
+	{
+		description:    "Substitute / Replace string with regex",
+		subdescription: "This uses golang regex, described [here](https://github.com/google/re2/wiki/Syntax)\nNote the use of `|=` to run in context of the current string value.",
+		document:       "a: cat\nb: heat",
+		expression:     `.[] |= sub("(a)", "${1}r")`,
+		expected: []string{
+			"D0, P[], (doc)::a: cart\nb: heart\n",
+		},
+	},
 	{
 		description: "Split strings",
 		document:    `"cat; meow; 1; ; true"`,

pkg/yqlib/operator_subtract.go

@@ -25,7 +25,7 @@ func subtractAssignOperator(d *dataTreeNavigator, context Context, expressionNod
 func subtractOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("Subtract operator")
 
-	return crossFunction(d, context, expressionNode, subtract)
+	return crossFunction(d, context, expressionNode, subtract, false)
 }
 
 func subtract(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {

pkg/yqlib/operators.go

@@ -24,7 +24,20 @@ func emptyOperator(d *dataTreeNavigator, context Context, expressionNode *Expres
 
 type crossFunctionCalculation func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error)
 
-func doCrossFunc(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode, calculation crossFunctionCalculation) (Context, error) {
+func resultsForRhs(d *dataTreeNavigator, context Context, lhsCandidate *CandidateNode, rhs Context, calculation crossFunctionCalculation, results *list.List) error {
+	for rightEl := rhs.MatchingNodes.Front(); rightEl != nil; rightEl = rightEl.Next() {
+		log.Debugf("Applying calc")
+		rhsCandidate := rightEl.Value.(*CandidateNode)
+		resultCandidate, err := calculation(d, context, lhsCandidate, rhsCandidate)
+		if err != nil {
+			return err
+		}
+		results.PushBack(resultCandidate)
+	}
+	return nil
+}
+
+func doCrossFunc(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode, calculation crossFunctionCalculation, calcWhenEmpty bool) (Context, error) {
 	var results = list.New()
 	lhs, err := d.GetMatchingNodes(context, expressionNode.Lhs)
 	if err != nil {
@@ -38,24 +51,33 @@ func doCrossFunc(d *dataTreeNavigator, context Context, expressionNode *Expressi
 		return Context{}, err
 	}
 
-	for el := lhs.MatchingNodes.Front(); el != nil; el = el.Next() {
-		lhsCandidate := el.Value.(*CandidateNode)
-
-		for rightEl := rhs.MatchingNodes.Front(); rightEl != nil; rightEl = rightEl.Next() {
-			log.Debugf("Applying calc")
-			rhsCandidate := rightEl.Value.(*CandidateNode)
-			resultCandidate, err := calculation(d, context, lhsCandidate, rhsCandidate)
+	if calcWhenEmpty && lhs.MatchingNodes.Len() == 0 {
+		if rhs.MatchingNodes.Len() == 0 {
+			resultCandidate, err := calculation(d, context, nil, nil)
 			if err != nil {
 				return Context{}, err
 			}
 			results.PushBack(resultCandidate)
 		}
+		err := resultsForRhs(d, context, nil, rhs, calculation, results)
+		if err != nil {
+			return Context{}, err
+		}
+	}
+
+	for el := lhs.MatchingNodes.Front(); el != nil; el = el.Next() {
+		lhsCandidate := el.Value.(*CandidateNode)
+
+		err := resultsForRhs(d, context, lhsCandidate, rhs, calculation, results)
+		if err != nil {
+			return Context{}, err
+		}
 
 	}
 	return context.ChildContext(results), nil
 }
 
-func crossFunction(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode, calculation crossFunctionCalculation) (Context, error) {
+func crossFunction(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode, calculation crossFunctionCalculation, calcWhenEmpty bool) (Context, error) {
 	var results = list.New()
 
 	var evaluateAllTogether = true
@@ -66,11 +88,11 @@ func crossFunction(d *dataTreeNavigator, context Context, expressionNode *Expres
 		}
 	}
 	if evaluateAllTogether {
-		return doCrossFunc(d, context, expressionNode, calculation)
+		return doCrossFunc(d, context, expressionNode, calculation, calcWhenEmpty)
 	}
 
 	for matchEl := context.MatchingNodes.Front(); matchEl != nil; matchEl = matchEl.Next() {
-		innerResults, err := doCrossFunc(d, context.SingleChildContext(matchEl.Value.(*CandidateNode)), expressionNode, calculation)
+		innerResults, err := doCrossFunc(d, context.SingleChildContext(matchEl.Value.(*CandidateNode)), expressionNode, calculation, calcWhenEmpty)
 		if err != nil {
 			return Context{}, err
 		}

release_instructions.txt

@@ -2,7 +2,7 @@
 - increment version in snapcraft.yaml
 - increment version in github-action/Dockerfile
 - make sure local build passes
-- run gosec (manual because docker platforms)
+- run ./scripts/secure.sh (manual because docker platforms)
 - commit version update changes
 - tag git with same version number
 - commit vX tag - this will trigger github actions

snap/snapcraft.yaml

@@ -1,5 +1,5 @@
 name: yq
-version: '4.6.3'
+version: '4.7.1'
 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.