ensure newline at end of formatted .env files

pkg/file.go

@@ -1,6 +1,7 @@
 package pkg
 
 import (
+	"fmt"
 	"io"
 	"os"
 
@@ -27,7 +28,12 @@ func Save(filename string, doc *ast.Document) error {
 	}
 	defer f.Close()
 
-	_, err = f.WriteString(render.NewFormatter().Statement(doc))
+	res := render.NewFormatter().Statement(doc)
+	if len(res) == 0 {
+		return fmt.Errorf("The rendered .env file is unexpectedly 0 bytes long - please report this as a bug (unless your file is empty)")
+	}
+
+	_, err = f.WriteString(res)
 
 	return err
 }

pkg/render/line_buffer.go

@@ -1,21 +1,18 @@
 package render
 
-import "strings"
+import (
+	"strings"
+	"unicode"
+)
+
+const Newline = "\n"
 
 type LineBuffer struct {
 	lines []string
 }
 
 func (lb *LineBuffer) Add(str string) *LineBuffer {
-	if len(str) == 0 {
-		return lb
-	}
-
-	if str == "\n" {
-		str = ""
-	}
-
-	lb.lines = append(lb.lines, str)
+	lb.AddPrinted(str)
 
 	return lb
 }
@@ -25,7 +22,7 @@ func (lb *LineBuffer) AddPrinted(str string) bool {
 		return false
 	}
 
-	if str == "\n" {
+	if str == Newline {
 		str = ""
 	}
 
@@ -35,9 +32,24 @@ func (lb *LineBuffer) AddPrinted(str string) bool {
 }
 
 func (lb *LineBuffer) Get() string {
-	return strings.Join(lb.lines, "\n")
+	return strings.Join(lb.lines, Newline)
 }
 
-func (lb *LineBuffer) Newline() {
+func (lb *LineBuffer) GetWithEOF() string {
+	return strings.TrimRightFunc(lb.Get(), unicode.IsSpace) + Newline
+}
+
+func (lb *LineBuffer) Newline() *LineBuffer {
 	lb.lines = append(lb.lines, "")
+
+	return lb
+}
+
+func (lb *LineBuffer) EnsureEOF() *LineBuffer {
+	idx := len(lb.lines) - 1
+	if idx > 0 && lb.lines[idx] != "" {
+		return lb.Newline()
+	}
+
+	return lb
 }

pkg/render/render.go

@@ -10,7 +10,6 @@ type Renderer struct {
 	Output   Outputter
 	Previous ast.Statement
 	Settings Settings
-
 	handlers []Handler
 }
 
@@ -25,7 +24,6 @@ func NewRenderer(settings Settings, handlers ...Handler) *Renderer {
 		Output:   output,
 		Previous: nil,
 		Settings: settings,
-
 		handlers: handlers,
 	}
 }
@@ -136,7 +134,7 @@ func (r *Renderer) Document(doc *ast.Document) string {
 	return out.
 		Add(r.Statement(doc.Statements)).
 		Add(r.Statement(doc.Groups)).
-		Get()
+		GetWithEOF()
 }
 
 func (r *Renderer) Group(group *ast.Group) string {

pkg/render/test-fixtures/formatter/comment-spacing.golden.env

@@ -2,4 +2,4 @@
 KEY=VALUE
 
 # My Second Key
-FOO=BAZ
+FOO=BAZ

pkg/render/test-fixtures/formatter/empty.golden.env

@@ -0,0 +1 @@
+

pkg/render/test-fixtures/formatter/just-a-comment.golden.env

@@ -1 +1 @@
-# Hello world
+# Hello world

pkg/render/test-fixtures/formatter/single-pair.golden.env

@@ -1 +1 @@
-KEY=VALUE
+KEY=VALUE

pkg/render/test-fixtures/formatter/two-pairs-newlines.golden.env

@@ -1,2 +1,2 @@
 KEY=VALUE
-FOO=baz
+FOO=baz

pkg/render/test-fixtures/formatter/two-pairs.golden.env

@@ -1,2 +1,2 @@
 KEY=VALUE
-FOO=baz
+FOO=baz