keep-blank-lines: preserve different line endings

Author: webner

template.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"bufio"
 	"bytes"
 	"crypto/sha1"
 	"encoding/json"
@@ -383,7 +382,9 @@ func generateFile(config Config, containers Context) bool {
 	contents := executeTemplate(config.Template, filteredContainers)
 
 	if !config.KeepBlankLines {
-		contents = removeBlankLines(contents)
+		buf := new(bytes.Buffer)
+		removeBlankLines(bytes.NewReader(contents), buf)
+		contents = buf.Bytes()
 	}
 
 	if config.Dest != "" {
@@ -433,22 +434,10 @@ func executeTemplate(templatePath string, containers Context) []byte {
 		log.Fatalf("unable to parse template: %s", err)
 	}
 
-	var buf bytes.Buffer
-	err = tmpl.ExecuteTemplate(&buf, filepath.Base(templatePath), &containers)
+	buf := new(bytes.Buffer)
+	err = tmpl.ExecuteTemplate(buf, filepath.Base(templatePath), &containers)
 	if err != nil {
 		log.Fatalf("template error: %s\n", err)
 	}
 	return buf.Bytes()
 }
-
-func removeBlankLines(buf []byte) []byte {
-	filtered := new(bytes.Buffer)
-	scanner := bufio.NewScanner(bytes.NewReader(buf))
-	for scanner.Scan() {
-		line := scanner.Text()
-		if !isBlank(line) {
-			fmt.Fprintln(filtered, line)
-		}
-	}
-	return filtered.Bytes()
-}

utils.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"bufio"
+	"io"
 	"os"
 	"strings"
 	"unicode"
@@ -60,3 +62,22 @@ func isBlank(str string) bool {
 	}
 	return true
 }
+
+func removeBlankLines(reader io.Reader, writer io.Writer) {
+	breader := bufio.NewReader(reader)
+	bwriter := bufio.NewWriter(writer)
+
+	for {
+		line, err := breader.ReadString('\n')
+
+		if !isBlank(line) {
+			bwriter.WriteString(line)
+		}
+
+		if err != nil {
+			break
+		}
+	}
+
+	bwriter.Flush()
+}

utils_test.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"bytes"
 	"flag"
 	"os"
+	"strings"
 	"testing"
 )
 
@@ -89,7 +91,6 @@ func TestSplitKeyValueSlice(t *testing.T) {
 }
 
 func TestIsBlank(t *testing.T) {
-
 	tests := []struct {
 		input    string
 		expected bool
@@ -113,3 +114,33 @@ func TestIsBlank(t *testing.T) {
 		}
 	}
 }
+
+func TestRemoveBlankLines(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"", ""},
+		{"\r\n\r\n", ""},
+		{"line1\nline2", "line1\nline2"},
+		{"line1\n\nline2", "line1\nline2"},
+		{"\n\n\n\nline1\n\nline2", "line1\nline2"},
+		{"\n\n\n\n\n  \n \n \n", ""},
+
+		// windows line endings \r\n
+		{"line1\r\nline2", "line1\r\nline2"},
+		{"line1\r\n\r\nline2", "line1\r\nline2"},
+
+		// keep last new line
+		{"line1\n", "line1\n"},
+		{"line1\r\n", "line1\r\n"},
+	}
+
+	for _, i := range tests {
+		output := new(bytes.Buffer)
+		removeBlankLines(strings.NewReader(i.input), output)
+		if output.String() != i.expected {
+			t.Fatalf("expected '%v'. got '%v'", i.expected, output)
+		}
+	}
+}