added path operator!

pkg/yqlib/doc/Path Operators.md

@@ -0,0 +1,59 @@
+The path operator can be used to find the traversal paths of matching nodes in an expression. The path is returned as an array, which if traversed in order will lead to the matching node.
+## Examples
+### Map path
+Given a sample.yml file of:
+```yaml
+a:
+  b: cat
+```
+then
+```bash
+yq eval '.a.b | path' sample.yml
+```
+will output
+```yaml
+- a
+- b
+```
+
+### Array path
+Given a sample.yml file of:
+```yaml
+a:
+  - cat
+  - dog
+```
+then
+```bash
+yq eval '.a.[] | select(. == "dog") | path' sample.yml
+```
+will output
+```yaml
+- a
+- 1
+```
+
+### Print path and value
+Given a sample.yml file of:
+```yaml
+a:
+  - cat
+  - dog
+  - frog
+```
+then
+```bash
+yq eval '.a.[] | select(. == "*og") | [{"path":path, "value":.}]' sample.yml
+```
+will output
+```yaml
+- path:
+    - a
+    - 1
+  value: dog
+- path:
+    - a
+    - 2
+  value: frog
+```
+

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

@@ -0,0 +1 @@
+The path operator can be used to find the traversal paths of matching nodes in an expression. The path is returned as an array, which if traversed in order will lead to the matching node.

pkg/yqlib/lib.go

@@ -17,7 +17,6 @@ type OperationType struct {
 }
 
 // operators TODO:
-// - get path operator (like doc index)
 // - write in place
 // - mergeAppend (merges and appends arrays)
 // - mergeEmpty (sets only if the document is empty, do I do that now?)
@@ -51,6 +50,7 @@ var GetComment = &OperationType{Type: "GET_COMMENT", NumArgs: 0, Precedence: 50,
 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}
+var GetPath = &OperationType{Type: "GET_PATH", NumArgs: 0, Precedence: 50, Handler: GetPathOperator}
 
 var Explode = &OperationType{Type: "EXPLODE", NumArgs: 1, Precedence: 50, Handler: ExplodeOperator}
 

pkg/yqlib/operator_path.go

@@ -0,0 +1,39 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func createPathNodeFor(pathElement interface{}) *yaml.Node {
+	switch pathElement := pathElement.(type) {
+	case string:
+		return &yaml.Node{Kind: yaml.ScalarNode, Value: pathElement, Tag: "!!str"}
+	default:
+		return &yaml.Node{Kind: yaml.ScalarNode, Value: fmt.Sprintf("%v", pathElement), Tag: "!!int"}
+	}
+}
+
+func GetPathOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
+	log.Debugf("GetPath")
+
+	var results = list.New()
+
+	for el := matchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		node := &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq"}
+
+		content := make([]*yaml.Node, len(candidate.Path))
+		for pathIndex := 0; pathIndex < len(candidate.Path); pathIndex++ {
+			path := candidate.Path[pathIndex]
+			content[pathIndex] = createPathNodeFor(path)
+		}
+		node.Content = content
+		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
+		results.PushBack(lengthCand)
+	}
+
+	return results, nil
+}

pkg/yqlib/operator_path_test.go

@@ -0,0 +1,45 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var pathOperatorScenarios = []expressionScenario{
+	{
+		description: "Map path",
+		document:    `{a: {b: cat}}`,
+		expression:  `.a.b | path`,
+		expected: []string{
+			"D0, P[a b], (!!seq)::- a\n- b\n",
+		},
+	},
+	{
+		description: "Array path",
+		document:    `{a: [cat, dog]}`,
+		expression:  `.a.[] | select(. == "dog") | path`,
+		expected: []string{
+			"D0, P[a 1], (!!seq)::- a\n- 1\n",
+		},
+	},
+	{
+		description: "Print path and value",
+		document:    `{a: [cat, dog, frog]}`,
+		expression:  `.a.[] | select(. == "*og") | [{"path":path, "value":.}]`,
+		expected: []string{`D0, P[], (!!seq)::- path:
+    - a
+    - 1
+  value: dog
+- path:
+    - a
+    - 2
+  value: frog
+`},
+	},
+}
+
+func TestPathOperatorsScenarios(t *testing.T) {
+	for _, tt := range pathOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Path Operators", pathOperatorScenarios)
+}

pkg/yqlib/path_tokeniser.go

@@ -206,6 +206,7 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`tag`), opAssignableToken(GetTag, AssignTag))
 	lexer.Add([]byte(`filename`), opToken(GetFilename))
 	lexer.Add([]byte(`fileIndex`), opToken(GetFileIndex))
+	lexer.Add([]byte(`path`), opToken(GetPath))
 
 	lexer.Add([]byte(`lineComment`), opTokenWithPrefs(GetComment, AssignComment, &CommentOpPreferences{LineComment: true}))