wip

acceptance_tests/empty.sh

@@ -9,7 +9,7 @@ EOL
 
 testEmptyEval() {
   X=$(./yq e test.yml)
-  expected=$(cat test.yml)
+  expected="# comment"
   assertEquals 0 $?
   assertEquals "$expected" "$X"
 }

pkg/yqlib/decoder_yaml.go

@@ -15,6 +15,7 @@ type yamlDecoder struct {
 	// work around of various parsing issues by yaml.v3 with document headers
 	prefs          YamlPreferences
 	leadingContent string
+	readAnything   bool
 }
 
 func NewYamlDecoder(prefs YamlPreferences) Decoder {
@@ -64,6 +65,7 @@ func (dec *yamlDecoder) Init(reader io.Reader) error {
 		}
 	}
 	dec.leadingContent = leadingContent
+	dec.readAnything = false
 	dec.decoder = *yaml.NewDecoder(readerToUse)
 	return nil
 }
@@ -72,7 +74,12 @@ func (dec *yamlDecoder) Decode() (*CandidateNode, error) {
 	var dataBucket yaml.Node
 
 	err := dec.decoder.Decode(&dataBucket)
-	if err != nil {
+	if errors.Is(err, io.EOF) && dec.leadingContent != "" && !dec.readAnything {
+		// force returning an empty node with a comment.
+		dec.readAnything = true
+		return dec.blankNodeWithComment(), nil
+
+	} else if err != nil {
 		return nil, err
 	}
 
@@ -90,3 +97,13 @@ func (dec *yamlDecoder) Decode() (*CandidateNode, error) {
 	dataBucket.FootComment = ""
 	return candidateNode, nil
 }
+
+func (dec *yamlDecoder) blankNodeWithComment() *CandidateNode {
+	return &CandidateNode{
+		Document:       0,
+		Filename:       "",
+		Node:           &yaml.Node{Kind: yaml.DocumentNode, Content: []*yaml.Node{{Tag: "!!null", Kind: yaml.ScalarNode}}},
+		FileIndex:      0,
+		LeadingContent: dec.leadingContent,
+	}
+}

pkg/yqlib/doc/usage/xml.md

@@ -386,6 +386,7 @@ A best attempt is made to copy comments to xml.
 
 Given a sample.yml file of:
 ```yaml
+# header comment
 # above_cat
 cat: # inline_cat
   # above_array
@@ -402,7 +403,10 @@ yq -o=xml '.' sample.yml
 ```
 will output
 ```xml
-<!-- inline_cat --><cat><!-- above_array inline_array -->
+<!--
+ header comment
+ above_cat
+ --><!-- inline_cat --><cat><!-- above_array inline_array -->
   <array>val1<!-- inline_val1 --></array>
   <array><!-- above_val2 -->val2<!-- inline_val2 --></array>
 </cat><!-- below_cat -->

pkg/yqlib/encoder_xml.go

@@ -4,24 +4,28 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
+	"regexp"
 	"strings"
 
 	yaml "gopkg.in/yaml.v3"
 )
 
 type xmlEncoder struct {
-	indentString string
-	writer       io.Writer
-	prefs        XmlPreferences
+	indentString   string
+	writer         io.Writer
+	prefs          XmlPreferences
+	leadingContent string
 }
 
+var commentPrefix = regexp.MustCompile(`(^|\n)\s*#`)
+
 func NewXMLEncoder(indent int, prefs XmlPreferences) Encoder {
 	var indentString = ""
 
 	for index := 0; index < indent; index++ {
 		indentString = indentString + " "
 	}
-	return &xmlEncoder{indentString, nil, prefs}
+	return &xmlEncoder{indentString, nil, prefs, ""}
 }
 
 func (e *xmlEncoder) CanHandleAliases() bool {
@@ -33,6 +37,7 @@ func (e *xmlEncoder) PrintDocumentSeparator(writer io.Writer) error {
 }
 
 func (e *xmlEncoder) PrintLeadingContent(writer io.Writer, content string) error {
+	e.leadingContent = commentPrefix.ReplaceAllString(content, "\n")
 	return nil
 }
 
@@ -42,6 +47,13 @@ func (e *xmlEncoder) Encode(writer io.Writer, node *yaml.Node) error {
 	e.writer = writer
 	encoder.Indent("", e.indentString)
 
+	if e.leadingContent != "" {
+		err := e.encodeComment(encoder, e.leadingContent)
+		if err != nil {
+			return err
+		}
+	}
+
 	switch node.Kind {
 	case yaml.MappingNode:
 		err := e.encodeTopLevelMap(encoder, node)

pkg/yqlib/operator_load_test.go

@@ -7,8 +7,16 @@ import (
 var loadScenarios = []expressionScenario{
 	{
 		skipDoc:     true,
-		description: "Load empty file",
+		description: "Load empty file with a comment",
 		expression:  `load("../../examples/empty.yaml")`,
+		expected: []string{
+			"D0, P[], (doc)::# comment\n\n",
+		},
+	},
+	{
+		skipDoc:     true,
+		description: "Load empty file with no comment",
+		expression:  `load("../../examples/empty-no-comment.yaml")`,
 		expected: []string{
 			"D0, P[], (!!null)::\n",
 		},

pkg/yqlib/printer.go

@@ -111,7 +111,7 @@ func (p *resultsPrinter) PrintResults(matchingNodes *list.List) error {
 
 		mappedDoc := el.Value.(*CandidateNode)
 		log.Debug("-- print sep logic: p.firstTimePrinting: %v, previousDocIndex: %v, mappedDoc.Document: %v", p.firstTimePrinting, p.previousDocIndex, mappedDoc.Document)
-
+		log.Debug("%v", NodeToString(mappedDoc))
 		writer, errorWriting := p.printerWriter.GetWriter(mappedDoc)
 		if errorWriting != nil {
 			return errorWriting

pkg/yqlib/stream_evaluator.go

@@ -75,6 +75,7 @@ func (s *streamEvaluator) EvaluateFiles(expression string, filenames []string, p
 	}
 
 	if totalProcessDocs == 0 {
+		// problem is I've already slurped the leading content sadface
 		return s.EvaluateNew(expression, printer)
 	}
 

pkg/yqlib/xml_test.go

@@ -137,7 +137,8 @@ in d before -->
 </cat><!-- after cat -->
 `
 
-const yamlWithComments = `# above_cat
+const yamlWithComments = `# header comment
+# above_cat
 cat: # inline_cat
   # above_array
   array: # inline_array
@@ -147,7 +148,10 @@ cat: # inline_cat
 # below_cat
 `
 
-const expectedXMLWithComments = `<!-- above_cat inline_cat --><cat><!-- above_array inline_array -->
+const expectedXMLWithComments = `<!--
+ header comment
+ above_cat
+ --><!-- inline_cat --><cat><!-- above_array inline_array -->
   <array>val1<!-- inline_val1 --></array>
   <array><!-- above_val2 -->val2<!-- inline_val2 --></array>
 </cat><!-- below_cat -->