Added flatten operator

pkg/yqlib/doc/Flatten.md

@@ -0,0 +1,70 @@
+This recursively flattens arrays.
+
+## Flatten
+Recursively flattens all arrays
+
+Given a sample.yml file of:
+```yaml
+- 1
+- - 2
+- - - 3
+```
+then
+```bash
+yq eval 'flatten' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- 3
+```
+
+## Flatten with depth of one
+Given a sample.yml file of:
+```yaml
+- 1
+- - 2
+- - - 3
+```
+then
+```bash
+yq eval 'flatten(1)' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- - 3
+```
+
+## Flatten empty array
+Given a sample.yml file of:
+```yaml
+- []
+```
+then
+```bash
+yq eval 'flatten' sample.yml
+```
+will output
+```yaml
+[]
+```
+
+## Flatten array of objects
+Given a sample.yml file of:
+```yaml
+- foo: bar
+- - foo: baz
+```
+then
+```bash
+yq eval 'flatten' sample.yml
+```
+will output
+```yaml
+- foo: bar
+- foo: baz
+```
+

pkg/yqlib/doc/headers/Flatten.md

@@ -0,0 +1 @@
+This recursively flattens arrays.

pkg/yqlib/expression_tokeniser.go

@@ -131,20 +131,40 @@ func opTokenWithPrefs(op *operationType, assignOpType *operationType, preference
 	}
 }
 
-func encodeWithIndent(outputFormat PrinterOutputFormat) lex.Action {
-	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
-
+func extractNumberParamter(value string) (int, error) {
 	parameterParser := regexp.MustCompile(`.*\(([0-9]+)\)`)
-		value := string(m.Bytes)
 	matches := parameterParser.FindStringSubmatch(value)
-
 	var indent, errParsingInt = strconv.ParseInt(matches[1], 10, 32) // nolint
+	if errParsingInt != nil {
+		return 0, errParsingInt
+	}
+	return int(indent), nil
+}
+
+func flattenWithDepth() lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		value := string(m.Bytes)
+		var depth, errParsingInt = extractNumberParamter(value)
 		if errParsingInt != nil {
 			return nil, errParsingInt
 		}
 
-		prefs := encoderPreferences{format: outputFormat, indent: int(indent)}
-		op := &Operation{OperationType: encodeOpType, Value: encodeOpType.Type, StringValue: value + "i " + matches[1], Preferences: prefs}
+		prefs := flattenPreferences{depth: depth}
+		op := &Operation{OperationType: flattenOpType, Value: flattenOpType.Type, StringValue: value, Preferences: prefs}
+		return &token{TokenType: operationToken, Operation: op}, nil
+	}
+}
+
+func encodeWithIndent(outputFormat PrinterOutputFormat) lex.Action {
+	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
+		value := string(m.Bytes)
+		var indent, errParsingInt = extractNumberParamter(value)
+		if errParsingInt != nil {
+			return nil, errParsingInt
+		}
+
+		prefs := encoderPreferences{format: outputFormat, indent: indent}
+		op := &Operation{OperationType: encodeOpType, Value: encodeOpType.Type, StringValue: value, Preferences: prefs}
 		return &token{TokenType: operationToken, Operation: op}, nil
 	}
 }
@@ -292,6 +312,9 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`:\s*`), opToken(createMapOpType))
 	lexer.Add([]byte(`length`), opToken(lengthOpType))
 
+	lexer.Add([]byte(`flatten\([0-9]+\)`), flattenWithDepth())
+	lexer.Add([]byte(`flatten`), opTokenWithPrefs(flattenOpType, nil, flattenPreferences{depth: -1}))
+
 	lexer.Add([]byte(`toyaml\([0-9]+\)`), encodeWithIndent(YamlOutputFormat))
 	lexer.Add([]byte(`to_yaml\([0-9]+\)`), encodeWithIndent(YamlOutputFormat))
 

pkg/yqlib/lib.go

@@ -114,6 +114,7 @@ var hasOpType = &operationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler:
 var uniqueOpType = &operationType{Type: "UNIQUE", NumArgs: 0, Precedence: 50, Handler: unique}
 var uniqueByOpType = &operationType{Type: "UNIQUE_BY", NumArgs: 1, Precedence: 50, Handler: uniqueBy}
 var groupByOpType = &operationType{Type: "GROUP_BY", NumArgs: 1, Precedence: 50, Handler: groupBy}
+var flattenOpType = &operationType{Type: "FLATTEN_BY", NumArgs: 0, Precedence: 50, Handler: flattenOp}
 var deleteChildOpType = &operationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: deleteChildOperator}
 
 type Operation struct {

pkg/yqlib/operator_flatten.go

@@ -0,0 +1,54 @@
+package yqlib
+
+import (
+	"fmt"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+type flattenPreferences struct {
+	depth int
+}
+
+func flatten(node *yaml.Node, depth int) {
+	if depth == 0 {
+		return
+	}
+	if node.Kind != yaml.SequenceNode {
+		return
+	}
+	content := node.Content
+	newSeq := make([]*yaml.Node, 0)
+
+	for i := 0; i < len(content); i++ {
+		if content[i].Kind == yaml.SequenceNode {
+			flatten(content[i], depth-1)
+			for j := 0; j < len(content[i].Content); j++ {
+				newSeq = append(newSeq, content[i].Content[j])
+			}
+		} else {
+			newSeq = append(newSeq, content[i])
+		}
+	}
+	node.Content = newSeq
+}
+
+func flattenOp(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+
+	log.Debugf("-- flatten Operator")
+	depth := expressionNode.Operation.Preferences.(flattenPreferences).depth
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		candidateNode := unwrapDoc(candidate.Node)
+		if candidateNode.Kind != yaml.SequenceNode {
+			return Context{}, fmt.Errorf("Only arrays are supported for group by")
+		}
+
+		flatten(candidateNode, depth)
+
+	}
+
+	return context, nil
+
+}

pkg/yqlib/operator_flatten_test.go

@@ -0,0 +1,48 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var flattenOperatorScenarios = []expressionScenario{
+	{
+		description:    "Flatten",
+		subdescription: "Recursively flattens all arrays",
+		document:       `[1, [2], [[3]]]`,
+		expression:     `flatten`,
+		expected: []string{
+			"D0, P[], (doc)::[1, 2, 3]\n",
+		},
+	},
+	{
+		description: "Flatten with depth of one",
+		document:    `[1, [2], [[3]]]`,
+		expression:  `flatten(1)`,
+		expected: []string{
+			"D0, P[], (doc)::[1, 2, [3]]\n",
+		},
+	},
+	{
+		description: "Flatten empty array",
+		document:    `[[]]`,
+		expression:  `flatten`,
+		expected: []string{
+			"D0, P[], (doc)::[]\n",
+		},
+	},
+	{
+		description: "Flatten array of objects",
+		document:    `[{foo: bar}, [{foo: baz}]]`,
+		expression:  `flatten`,
+		expected: []string{
+			"D0, P[], (doc)::[{foo: bar}, {foo: baz}]\n",
+		},
+	},
+}
+
+func TestFlattenOperatorScenarios(t *testing.T) {
+	for _, tt := range flattenOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Flatten", flattenOperatorScenarios)
+}

release_notes.txt

@@ -1,3 +1,8 @@
+4.14.1:
+  - Added group_by operator
+  - Added encode/decode operators (toyaml, fromjson etc)
+  - Added flatten operator
+
 4.13.5:
   - Performance improvement for deepMatch (thanks @pmatseykanets)
   - Added manpage, included in tar.gz downloads as well as a separate tar.gz (#961)