Adding magic to detect leading seperators

examples/data1.yaml

@@ -1 +1,2 @@
+---
 {"a":{"b":1}}

examples/leading-seperator.yaml

@@ -0,0 +1,2 @@
+---
+a: test

pkg/yqlib/all_at_once_evaluator.go

@@ -48,13 +48,19 @@ func (e *allAtOnceEvaluator) EvaluateCandidateNodes(expression string, inputCand
 
 func (e *allAtOnceEvaluator) EvaluateFiles(expression string, filenames []string, printer Printer) error {
 	fileIndex := 0
+	firstFileLeadingSeperator := false
 
 	var allDocuments *list.List = list.New()
 	for _, filename := range filenames {
-		reader, err := readStream(filename)
+		reader, leadingSeperator, err := readStream(filename)
 		if err != nil {
 			return err
 		}
+
+		if fileIndex == 0 && leadingSeperator {
+			firstFileLeadingSeperator = leadingSeperator
+		}
+
 		fileDocuments, err := readDocuments(reader, filename, fileIndex)
 		if err != nil {
 			return err
@@ -66,5 +72,6 @@ func (e *allAtOnceEvaluator) EvaluateFiles(expression string, filenames []string
 	if err != nil {
 		return err
 	}
+	printer.SetPrintLeadingSeperator(firstFileLeadingSeperator)
 	return printer.PrintResults(matches)
 }

pkg/yqlib/printer.go

@@ -11,6 +11,7 @@ import (
 type Printer interface {
 	PrintResults(matchingNodes *list.List) error
 	PrintedAnything() bool
+	SetPrintLeadingSeperator(bool)
 }
 
 type resultsPrinter struct {
@@ -40,6 +41,13 @@ func NewPrinter(writer io.Writer, outputToJSON bool, unwrapScalar bool, colorsEn
 	}
 }
 
+func (p *resultsPrinter) SetPrintLeadingSeperator(printLeadingSeperator bool) {
+	if printLeadingSeperator {
+		p.firstTimePrinting = false
+		p.previousFileIndex = -1
+	}
+}
+
 func (p *resultsPrinter) PrintedAnything() bool {
 	return p.printedMatches
 }

pkg/yqlib/printer_test.go

@@ -17,12 +17,36 @@ a: apple
 a: coconut
 `
 
+var leadingSeperatorSample = `---
+a: good doc
+`
+
 func nodeToList(candidate *CandidateNode) *list.List {
 	elMap := list.New()
 	elMap.PushBack(candidate)
 	return elMap
 }
 
+func TestPrinterWithLeadingSeperator(t *testing.T) {
+	var output bytes.Buffer
+	var writer = bufio.NewWriter(&output)
+	printer := NewPrinter(writer, false, true, false, 2, true)
+
+	inputs, err := readDocuments(strings.NewReader(leadingSeperatorSample), "sample.yml", 0)
+	if err != nil {
+		panic(err)
+	}
+	printer.SetPrintLeadingSeperator(true)
+
+	err = printer.PrintResults(inputs)
+	if err != nil {
+		panic(err)
+	}
+
+	writer.Flush()
+	test.AssertResult(t, leadingSeperatorSample, output.String())
+}
+
 func TestPrinterMultipleDocsInSequence(t *testing.T) {
 	var output bytes.Buffer
 	var writer = bufio.NewWriter(&output)

pkg/yqlib/stream_evaluator.go

@@ -55,8 +55,11 @@ func (s *streamEvaluator) EvaluateFiles(expression string, filenames []string, p
 		return err
 	}
 
-	for _, filename := range filenames {
+	for index, filename := range filenames {
-		reader, err := readStream(filename)
+		reader, leadingSeperator, err := readStream(filename)
+		if index == 0 && leadingSeperator {
+			printer.SetPrintLeadingSeperator(leadingSeperator)
+		}
 		if err != nil {
 			return err
 		}

pkg/yqlib/utils.go

@@ -9,13 +9,28 @@ import (
 	yaml "gopkg.in/yaml.v3"
 )
 
-func readStream(filename string) (io.Reader, error) {
+func readStream(filename string) (io.Reader, bool, error) {
+
 	if filename == "-" {
-		return bufio.NewReader(os.Stdin), nil
+		reader := bufio.NewReader(os.Stdin)
+
+		seperatorBytes, err := reader.Peek(3)
+		return reader, string(seperatorBytes) == "---", err
 	} else {
 		// ignore CWE-22 gosec issue - that's more targetted for http based apps that run in a public directory,
 		// and ensuring that it's not possible to give a path to a file outside thar directory.
-		return os.Open(filename) // #nosec
+		reader, err := os.Open(filename)
+		if err != nil {
+			return nil, false, err
+		}
+		seperatorBytes := make([]byte, 3)
+		_, err = reader.Read(seperatorBytes)
+		if err != nil {
+			return nil, false, err
+		}
+		_, err = reader.Seek(0, 0)
+
+		return reader, string(seperatorBytes) == "---", err
 	}
 }
 

scripts/acceptance.sh

@@ -55,6 +55,64 @@ if [[ $? != 1 ]]; then
   exit 1
 fi
 
+# Test leading seperator logic
+expected=$(cat examples/leading-seperator.yaml)
+
+X=$(cat examples/leading-seperator.yaml | ./yq e '.' -)
+if [[ $X != $expected ]]; then
+  echo "Pipe into e"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
+X=$(./yq e '.' examples/leading-seperator.yaml)
+expected=$(cat examples/leading-seperator.yaml)
+if [[ $X != $expected ]]; then
+  echo "read given file e"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
+X=$(cat examples/leading-seperator.yaml | ./yq ea '.' -)
+if [[ $X != $expected ]]; then
+  echo "Pipe into e"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
+X=$(./yq ea '.' examples/leading-seperator.yaml)
+expected=$(cat examples/leading-seperator.yaml)
+if [[ $X != $expected ]]; then
+  echo "read given file e"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
+# multidoc
+read -r -d '' expected << EOM
+---
+a: test
+---
+version: 3
+application: MyApp
+EOM
+
+X=$(./yq e '.' examples/leading-seperator.yaml examples/order.yaml)
+
+if [[ $X != $expected ]]; then
+  echo "Multidoc with leading seperator"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
+X=$(./yq ea '.' examples/leading-seperator.yaml examples/order.yaml)
+
+if [[ $X != $expected ]]; then
+  echo "Multidoc with leading seperator"
+  echo "Expected $expected but was $X"
+  exit 1
+fi
+
 echo "--success"
 
 set -e