Add operator!

pkg/yqlib/doc/Add.md

@@ -0,0 +1,107 @@
+Add behaves differently according to the type of the LHS:
+- arrays: concatenate
+- number scalars: arithmetic addition (soon)
+- string scalars: concatenate (soon)
+## Concatenate arrays
+Given a sample.yml file of:
+```yaml
+a:
+  - 1
+  - 2
+b:
+  - 3
+  - 4
+```
+then
+```bash
+yq eval '.a + .b' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- 3
+- 4
+```
+
+## Concatenate null to array
+Given a sample.yml file of:
+```yaml
+a:
+  - 1
+  - 2
+```
+then
+```bash
+yq eval '.a + null' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+```
+
+## Add object to array
+Given a sample.yml file of:
+```yaml
+a:
+  - 1
+  - 2
+c:
+  cat: meow
+```
+then
+```bash
+yq eval '.a + .c' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- cat: meow
+```
+
+## Add string to array
+Given a sample.yml file of:
+```yaml
+a:
+  - 1
+  - 2
+```
+then
+```bash
+yq eval '.a + "hello"' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- hello
+```
+
+## Update array (append)
+Given a sample.yml file of:
+```yaml
+a:
+  - 1
+  - 2
+b:
+  - 3
+  - 4
+```
+then
+```bash
+yq eval '.a = .a + .b' sample.yml
+```
+will output
+```yaml
+a:
+  - 1
+  - 2
+  - 3
+  - 4
+b:
+  - 3
+  - 4
+```
+

pkg/yqlib/doc/headers/Add.md

@@ -0,0 +1,4 @@
+Add behaves differently according to the type of the LHS:
+- arrays: concatenate
+- number scalars: arithmetic addition (soon)
+- string scalars: concatenate (soon)

pkg/yqlib/lib.go

@@ -36,7 +36,8 @@ 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 Multiply = &OperationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 40, Handler: MultiplyOperator}
+var Multiply = &OperationType{Type: "MULTIPLY", NumArgs: 2, Precedence: 45, Handler: MultiplyOperator}
+var Add = &OperationType{Type: "ADD", NumArgs: 2, Precedence: 45, Handler: AddOperator}
 
 var Equals = &OperationType{Type: "EQUALS", NumArgs: 2, Precedence: 40, Handler: EqualsOperator}
 var CreateMap = &OperationType{Type: "CREATE_MAP", NumArgs: 2, Precedence: 40, Handler: CreateMapOperator}

pkg/yqlib/operator_add.go

@@ -0,0 +1,69 @@
+package yqlib
+
+import (
+	"fmt"
+
+	"container/list"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func toNodes(candidates *list.List) []*yaml.Node {
+
+	if candidates.Len() == 0 {
+		return []*yaml.Node{}
+	}
+	candidate := candidates.Front().Value.(*CandidateNode)
+
+	if candidate.Node.Tag == "!!null" {
+		return []*yaml.Node{}
+	}
+
+	switch candidate.Node.Kind {
+	case yaml.SequenceNode:
+		return candidate.Node.Content
+	default:
+		return []*yaml.Node{candidate.Node}
+	}
+
+}
+
+func AddOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+	log.Debugf("Add operator")
+	var results = list.New()
+	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
+	if err != nil {
+		return nil, err
+	}
+	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+
+	if err != nil {
+		return nil, err
+	}
+
+	for el := lhs.Front(); el != nil; el = el.Next() {
+		lhsCandidate := el.Value.(*CandidateNode)
+		lhsNode := UnwrapDoc(lhsCandidate.Node)
+
+		var newBlank = &CandidateNode{
+			Path:     lhsCandidate.Path,
+			Document: lhsCandidate.Document,
+			Filename: lhsCandidate.Filename,
+			Node:     &yaml.Node{},
+		}
+
+		switch lhsNode.Kind {
+		case yaml.MappingNode:
+			return nil, fmt.Errorf("Maps not yet supported for addition")
+		case yaml.SequenceNode:
+			newBlank.Node.Kind = yaml.SequenceNode
+			newBlank.Node.Style = lhsNode.Style
+			newBlank.Node.Tag = "!!seq"
+			newBlank.Node.Content = append(lhsNode.Content, toNodes(rhs)...)
+			results.PushBack(newBlank)
+		case yaml.ScalarNode:
+			return nil, fmt.Errorf("Scalars not yet supported for addition")
+		}
+	}
+	return results, nil
+}

pkg/yqlib/operator_add_test.go

@@ -0,0 +1,55 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var addOperatorScenarios = []expressionScenario{
+	{
+		description: "Concatenate arrays",
+		document:    `{a: [1,2], b: [3,4]}`,
+		expression:  `.a + .b`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[1, 2, 3, 4]\n",
+		},
+	},
+	{
+		description: "Concatenate null to array",
+		document:    `{a: [1,2]}`,
+		expression:  `.a + null`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[1, 2]\n",
+		},
+	},
+	{
+		description: "Add object to array",
+		document:    `{a: [1,2], c: {cat: meow}}`,
+		expression:  `.a + .c`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[1, 2, {cat: meow}]\n",
+		},
+	},
+	{
+		description: "Add string to array",
+		document:    `{a: [1,2]}`,
+		expression:  `.a + "hello"`,
+		expected: []string{
+			"D0, P[a], (!!seq)::[1, 2, hello]\n",
+		},
+	},
+	{
+		description: "Update array (append)",
+		document:    `{a: [1,2], b: [3,4]}`,
+		expression:  `.a = .a + .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: [1, 2, 3, 4], b: [3, 4]}\n",
+		},
+	},
+}
+
+func TestAddOperatorScenarios(t *testing.T) {
+	for _, tt := range addOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Add", addOperatorScenarios)
+}

pkg/yqlib/path_tokeniser.go

@@ -252,6 +252,7 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`\{`), literalToken(OpenCollectObject, false))
 	lexer.Add([]byte(`\}`), literalToken(CloseCollectObject, true))
 	lexer.Add([]byte(`\*`), opToken(Multiply))
+	lexer.Add([]byte(`\+`), opToken(Add))
 
 	err := lexer.Compile()
 	if err != nil {