Adds support for writing text files in Vacation

Signed-off-by: Timothy Hitchener <thitchener@pivotal.io>

postal/service_test.go

@@ -450,7 +450,8 @@ version = "this is super not semver"
 
 			context("when the file contents are empty", func() {
 				it.Before(func() {
-					buffer := bytes.NewBuffer(nil)
+					// This is a FLAC header
+					buffer := bytes.NewBuffer([]byte("\x66\x4C\x61\x43\x00\x00\x00\x22"))
 					transport.DropCall.Returns.ReadCloser = io.NopCloser(buffer)
 
 					sum := sha256.Sum256(buffer.Bytes())
@@ -703,7 +704,8 @@ version = "this is super not semver"
 
 			context("when the file contents are empty", func() {
 				it.Before(func() {
-					buffer := bytes.NewBuffer(nil)
+					// This is a FLAC header
+					buffer := bytes.NewBuffer([]byte("\x66\x4C\x61\x43\x00\x00\x00\x22"))
 					transport.DropCall.Returns.ReadCloser = io.NopCloser(buffer)
 
 					sum := sha256.Sum256(buffer.Bytes())

vacation/init_test.go

@@ -13,6 +13,7 @@ func TestVacation(t *testing.T) {
 	suite("VacationTar", testVacationTar)
 	suite("VacationTarGzip", testVacationTarGzip)
 	suite("VacationTarXZ", testVacationTarXZ)
+	suite("VacationText", testVacationText)
 	suite("VacationZip", testVacationZip)
 	suite.Run(t)
 }

vacation/vacation.go

@@ -141,7 +141,6 @@ func (ta TarArchive) Decompress(destination string) error {
 			if err != nil {
 				return fmt.Errorf("failed to extract symlink: %s", err)
 			}
-
 		}
 	}
 
@@ -150,6 +149,10 @@ func (ta TarArchive) Decompress(destination string) error {
 
 // Decompress reads from Archive, determines the archive type of the input
 // stream, and writes files into the destination specified.
+//
+// Archive decompression will also handle files that are types "text/plain;
+// charset=utf-8" and write the contents of the input stream to a file name
+// "artifact" in the destination directory.
 func (a Archive) Decompress(destination string) error {
 	// Convert reader into a buffered read so that the header can be peeked to
 	// determine the type.
@@ -176,6 +179,10 @@ func (a Archive) Decompress(destination string) error {
 		return NewTarXZArchive(bufferedReader).StripComponents(a.components).Decompress(destination)
 	case "application/zip":
 		return NewZipArchive(bufferedReader).Decompress(destination)
+	case "text/plain; charset=utf-8":
+		// This function will write the contents of the reader to file called
+		// "artifact" in the destination directory
+		return writeTextFile(bufferedReader, destination)
 	default:
 		return fmt.Errorf("unsupported archive type: %s", mime.String())
 	}
@@ -203,6 +210,20 @@ func (txz TarXZArchive) Decompress(destination string) error {
 	return NewTarArchive(xzr).StripComponents(txz.components).Decompress(destination)
 }
 
+func writeTextFile(reader io.Reader, destination string) error {
+	file, err := os.Create(filepath.Join(destination, "artifact"))
+	if err != nil {
+		panic(err)
+	}
+
+	_, err = io.Copy(file, reader)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // StripComponents behaves like the --strip-components flag on tar command
 // removing the first n levels from the final decompression destination.
 // Setting this is a no-op for archive types that do not use --strip-components

vacation/vacation_archive_test.go

@@ -264,7 +264,8 @@ func testVacationArchive(t *testing.T, context spec.G, it spec.S) {
 					tempDir, err = os.MkdirTemp("", "vacation")
 					Expect(err).NotTo(HaveOccurred())
 
-					buffer := bytes.NewBuffer([]byte(`some contents`))
+					// This is a FLAC header
+					buffer := bytes.NewBuffer([]byte("\x66\x4C\x61\x43\x00\x00\x00\x22"))
 
 					archive = vacation.NewArchive(buffer)
 				})

vacation/vacation_text_test.go

@@ -0,0 +1,49 @@
+package vacation_test
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/paketo-buildpacks/packit/vacation"
+	"github.com/sclevine/spec"
+
+	. "github.com/onsi/gomega"
+)
+
+func testVacationText(t *testing.T, context spec.G, it spec.S) {
+	var (
+		Expect = NewWithT(t).Expect
+	)
+
+	context("when passed the reader of a text file", func() {
+		var (
+			archive vacation.Archive
+			tempDir string
+		)
+
+		it.Before(func() {
+			var err error
+			tempDir, err = os.MkdirTemp("", "vacation")
+			Expect(err).NotTo(HaveOccurred())
+
+			buffer := bytes.NewBuffer([]byte(`some contents`))
+
+			archive = vacation.NewArchive(buffer)
+		})
+
+		it.After(func() {
+			Expect(os.RemoveAll(tempDir)).To(Succeed())
+		})
+
+		it("writes a text file onto the path", func() {
+			err := archive.Decompress(tempDir)
+			Expect(err).NotTo(HaveOccurred())
+
+			content, err := os.ReadFile(filepath.Join(tempDir, "artifact"))
+			Expect(err).NotTo(HaveOccurred())
+			Expect(content).To(Equal([]byte(`some contents`)))
+		})
+	})
+}