Fixed newline handling when decoding/encoding

pkg/yqlib/candidate_node.go

@@ -1,6 +1,7 @@
 package yqlib
 
 import (
+	"container/list"
 	"fmt"
 
 	"github.com/jinzhu/copier"
@@ -28,6 +29,12 @@ func (n *CandidateNode) GetKey() string {
 	return fmt.Sprintf("%v%v - %v", keyPrefix, n.Document, n.Path)
 }
 
+func (n *CandidateNode) AsList() *list.List {
+	elMap := list.New()
+	elMap.PushBack(n)
+	return elMap
+}
+
 func (n *CandidateNode) CreateChild(path interface{}, node *yaml.Node) *CandidateNode {
 	return &CandidateNode{
 		Node:      node,

pkg/yqlib/doc/Encoder and Decoder.md

@@ -92,11 +92,12 @@ b:
   foo: bar
 ```
 
-## Update an encoded yaml string
+## Update a multiline encoded yaml string
 Given a sample.yml file of:
 ```yaml
 a: |
   foo: bar
+  baz: dog
 ```
 then
 ```bash
@@ -106,5 +107,20 @@ will output
 ```yaml
 a: |
   foo: cat
+  baz: dog
+```
+
+## Update a single line encoded yaml string
+Given a sample.yml file of:
+```yaml
+a: 'foo: bar'
+```
+then
+```bash
+yq eval '.a |= (from_yaml | .foo = "cat" | to_yaml)' sample.yml
+```
+will output
+```yaml
+a: 'foo: cat'
 ```
 

pkg/yqlib/operator_encoder_decoder.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"container/list"
+	"regexp"
 	"strings"
 
 	"gopkg.in/yaml.v3"
@@ -12,9 +13,7 @@ import (
 func yamlToString(candidate *CandidateNode, prefs encoderPreferences) (string, error) {
 	var output bytes.Buffer
 	printer := NewPrinter(bufio.NewWriter(&output), prefs.format, true, false, 2, true)
-	elMap := list.New()
+	err := printer.PrintResults(candidate.AsList())
-	elMap.PushBack(candidate)
-	err := printer.PrintResults(elMap)
 	return output.String(), err
 }
 
@@ -27,13 +26,30 @@ type encoderPreferences struct {
 func encodeOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	preferences := expressionNode.Operation.Preferences.(encoderPreferences)
 	var results = list.New()
+
+	hasOnlyOneNewLine := regexp.MustCompile("[^\n].*\n$")
+	chomper := regexp.MustCompile("\n+$")
+
 	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		stringValue, err := yamlToString(candidate, preferences)
+
 		if err != nil {
 			return Context{}, err
 		}
 
+		// remove trailing newlines if needed.
+		// check if we originally decoded this path, and the original thing had a single line.
+		originalList := context.GetVariable("decoded: " + candidate.GetKey())
+		if originalList != nil && originalList.Len() > 0 && hasOnlyOneNewLine.MatchString(stringValue) {
+
+			original := originalList.Front().Value.(*CandidateNode)
+			if unwrapDoc(original.Node).Style == yaml.SingleQuotedStyle ||
+				unwrapDoc(original.Node).Style == yaml.DoubleQuotedStyle {
+				stringValue = chomper.ReplaceAllString(stringValue, "")
+			}
+		}
+
 		stringContentNode := &yaml.Node{Kind: yaml.ScalarNode, Tag: "!!str", Value: stringValue}
 		results.PushBack(candidate.CreateChild(nil, stringContentNode))
 	}
@@ -46,6 +62,9 @@ func decodeOperator(d *dataTreeNavigator, context Context, expressionNode *Expre
 	var results = list.New()
 	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
+
+		context.SetVariable("decoded: "+candidate.GetKey(), candidate.AsList())
+
 		var dataBucket yaml.Node
 		log.Debugf("got: [%v]", candidate.Node.Value)
 		decoder := yaml.NewDecoder(strings.NewReader(unwrapDoc(candidate.Node).Value))

pkg/yqlib/operator_encoder_decoder_test.go

@@ -51,12 +51,30 @@ var encoderDecoderOperatorScenarios = []expressionScenario{
 		},
 	},
 	{
-		description:           "Update an encoded yaml string",
+		description:           "Update a multiline encoded yaml string",
 		dontFormatInputForDoc: true,
-		document:              "a: |\n  foo: bar",
+		document:              "a: |\n  foo: bar\n  baz: dog",
 		expression:            `.a |= (from_yaml | .foo = "cat" | to_yaml)`,
 		expected: []string{
-			"D0, P[], (doc)::a: |\n    foo: cat\n",
+			"D0, P[], (doc)::a: |\n    foo: cat\n    baz: dog\n",
+		},
+	},
+	{
+		description:           "Update a single line encoded yaml string",
+		dontFormatInputForDoc: true,
+		document:              "a: 'foo: bar'",
+		expression:            `.a |= (from_yaml | .foo = "cat" | to_yaml)`,
+		expected: []string{
+			"D0, P[], (doc)::a: 'foo: cat'\n",
+		},
+	},
+	{
+		skipDoc:               true,
+		dontFormatInputForDoc: true,
+		document:              "a: \"foo: bar\"",
+		expression:            `.a |= (from_yaml | .foo = {"a": "frog"} | to_yaml)`,
+		expected: []string{
+			"D0, P[], (doc)::a: \"foo:\\n  a: frog\"\n",
 		},
 	},
 }