creates a fs.Copy function, (#28)

- re-uses most implementation from fs.Move

fs/copy.go

@@ -0,0 +1,131 @@
+package fs
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// Copy will move a source file or directory to a destination. For directories,
+// move will remap relative symlinks ensuring that they align with the
+// destination directory. If the destination exists prior to invocation, it
+// will be removed.
+func Copy(source, destination string) error {
+	err := os.Remove(destination)
+	if err != nil {
+		if !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("failed to copy: destination exists: %w", err)
+		}
+	}
+
+	info, err := os.Stat(source)
+	if err != nil {
+		return err
+	}
+
+	if info.IsDir() {
+		err = copyDirectory(source, destination)
+		if err != nil {
+			return err
+		}
+	} else {
+		err = copyFile(source, destination)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func copyFile(source, destination string) error {
+	sourceFile, err := os.Open(source)
+	if err != nil {
+		return err
+	}
+	defer sourceFile.Close()
+
+	destinationFile, err := os.Create(destination)
+	if err != nil {
+		return err
+	}
+	defer destinationFile.Close()
+
+	_, err = io.Copy(destinationFile, sourceFile)
+	if err != nil {
+		return err
+	}
+
+	info, err := sourceFile.Stat()
+	if err != nil {
+		return err
+	}
+
+	err = destinationFile.Chmod(info.Mode())
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func copyDirectory(source, destination string) error {
+	err := filepath.Walk(source, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		path, err = filepath.Rel(source, path)
+		if err != nil {
+			return err
+		}
+
+		switch {
+		case info.IsDir():
+			err = os.Mkdir(filepath.Join(destination, path), os.ModePerm)
+			if err != nil {
+				return err
+			}
+
+		case (info.Mode() & os.ModeSymlink) != 0:
+			link, err := os.Readlink(filepath.Join(source, path))
+			if err != nil {
+				return err
+			}
+
+			if filepath.HasPrefix(link, "..") {
+				link = filepath.Clean(filepath.Join(source, filepath.Base(path), link))
+			}
+
+			relativeLink, err := filepath.Rel(source, link)
+			if err != nil {
+				return err
+			}
+
+			if filepath.HasPrefix(relativeLink, "..") {
+				err = os.Symlink(link, filepath.Join(destination, path))
+			} else {
+				err = os.Symlink(filepath.Join(destination, relativeLink), filepath.Join(destination, path))
+			}
+			if err != nil {
+				return err
+			}
+
+		default:
+			err = copyFile(filepath.Join(source, path), filepath.Join(destination, path))
+			if err != nil {
+				return err
+			}
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

fs/copy_test.go

@@ -0,0 +1,211 @@
+package fs_test
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/paketo-buildpacks/packit/fs"
+	"github.com/sclevine/spec"
+
+	. "github.com/onsi/gomega"
+)
+
+func testCopy(t *testing.T, context spec.G, it spec.S) {
+	var Expect = NewWithT(t).Expect
+
+	context("Copy", func() {
+		var (
+			sourceDir      string
+			destinationDir string
+		)
+
+		it.Before(func() {
+			var err error
+			sourceDir, err = ioutil.TempDir("", "source")
+			Expect(err).NotTo(HaveOccurred())
+
+			destinationDir, err = ioutil.TempDir("", "destination")
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		it.After(func() {
+			Expect(os.RemoveAll(sourceDir)).To(Succeed())
+			Expect(os.RemoveAll(destinationDir)).To(Succeed())
+		})
+
+		context("when the source is a file", func() {
+			var source, destination string
+
+			it.Before(func() {
+				source = filepath.Join(sourceDir, "source")
+				destination = filepath.Join(destinationDir, "destination")
+
+				err := ioutil.WriteFile(source, []byte("some-content"), 0644)
+				Expect(err).NotTo(HaveOccurred())
+			})
+
+			it("copies the source file to the destination", func() {
+				err := fs.Copy(source, destination)
+				Expect(err).NotTo(HaveOccurred())
+
+				content, err := ioutil.ReadFile(destination)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(string(content)).To(Equal("some-content"))
+
+				info, err := os.Stat(destination)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(info.Mode()).To(Equal(os.FileMode(0644)))
+
+				Expect(source).To(BeAnExistingFile())
+			})
+
+			context("failure cases", func() {
+				context("when the source cannot be read", func() {
+					it.Before(func() {
+						Expect(os.Chmod(source, 0000)).To(Succeed())
+					})
+
+					it("returns an error", func() {
+						err := fs.Copy(source, destination)
+						Expect(err).To(MatchError(ContainSubstring("permission denied")))
+					})
+				})
+
+				context("when the destination cannot be removed", func() {
+					it.Before(func() {
+						Expect(os.Chmod(destinationDir, 0000)).To(Succeed())
+					})
+
+					it("returns an error", func() {
+						err := fs.Copy(source, destination)
+						Expect(err).To(MatchError(ContainSubstring("failed to copy: destination exists:")))
+						Expect(err).To(MatchError(ContainSubstring("permission denied")))
+					})
+				})
+			})
+		})
+
+		context("when the source is a directory", func() {
+			var source, destination, external string
+
+			it.Before(func() {
+				var err error
+				external, err = ioutil.TempDir("", "external")
+				Expect(err).NotTo(HaveOccurred())
+
+				err = ioutil.WriteFile(filepath.Join(external, "some-file"), []byte("some-content"), 0644)
+				Expect(err).NotTo(HaveOccurred())
+
+				source = filepath.Join(sourceDir, "source")
+				destination = filepath.Join(destinationDir, "destination")
+
+				Expect(os.MkdirAll(filepath.Join(source, "some-dir"), os.ModePerm)).To(Succeed())
+
+				err = ioutil.WriteFile(filepath.Join(source, "some-dir", "some-file"), []byte("some-content"), 0644)
+				Expect(err).NotTo(HaveOccurred())
+
+				err = ioutil.WriteFile(filepath.Join(source, "some-dir", "readonly-file"), []byte("some-content"), 0444)
+				Expect(err).NotTo(HaveOccurred())
+
+				err = os.Symlink(filepath.Join(source, "some-dir", "some-file"), filepath.Join(source, "some-dir", "some-symlink"))
+				Expect(err).NotTo(HaveOccurred())
+
+				err = os.Symlink(filepath.Join(external, "some-file"), filepath.Join(source, "some-dir", "external-symlink"))
+				Expect(err).NotTo(HaveOccurred())
+			})
+
+			context("when the destination does not exist", func() {
+				it("copies the source directory to the destination", func() {
+					err := fs.Copy(source, destination)
+					Expect(err).NotTo(HaveOccurred())
+
+					Expect(destination).To(BeADirectory())
+
+					content, err := ioutil.ReadFile(filepath.Join(destination, "some-dir", "some-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(string(content)).To(Equal("some-content"))
+
+					info, err := os.Stat(filepath.Join(destination, "some-dir", "some-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(info.Mode()).To(Equal(os.FileMode(0644)))
+
+					info, err = os.Stat(filepath.Join(destination, "some-dir", "readonly-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(info.Mode()).To(Equal(os.FileMode(0444)))
+
+					path, err := os.Readlink(filepath.Join(destination, "some-dir", "some-symlink"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(path).To(Equal(filepath.Join(destination, "some-dir", "some-file")))
+
+					path, err = os.Readlink(filepath.Join(destination, "some-dir", "external-symlink"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(path).To(Equal(filepath.Join(external, "some-file")))
+
+					Expect(source).To(BeAnExistingFile())
+				})
+			})
+
+			context("when the destination is a file", func() {
+				it.Before(func() {
+					Expect(os.RemoveAll(destination))
+					Expect(ioutil.WriteFile(destination, []byte{}, os.ModePerm)).To(Succeed())
+				})
+
+				it("copies the source directory to the destination", func() {
+					err := fs.Copy(source, destination)
+					Expect(err).NotTo(HaveOccurred())
+
+					Expect(destination).To(BeADirectory())
+
+					content, err := ioutil.ReadFile(filepath.Join(destination, "some-dir", "some-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(string(content)).To(Equal("some-content"))
+
+					info, err := os.Stat(filepath.Join(destination, "some-dir", "some-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(info.Mode()).To(Equal(os.FileMode(0644)))
+
+					info, err = os.Stat(filepath.Join(destination, "some-dir", "readonly-file"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(info.Mode()).To(Equal(os.FileMode(0444)))
+
+					path, err := os.Readlink(filepath.Join(destination, "some-dir", "some-symlink"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(path).To(Equal(filepath.Join(destination, "some-dir", "some-file")))
+
+					path, err = os.Readlink(filepath.Join(destination, "some-dir", "external-symlink"))
+					Expect(err).NotTo(HaveOccurred())
+					Expect(path).To(Equal(filepath.Join(external, "some-file")))
+
+					Expect(source).To(BeAnExistingFile())
+				})
+			})
+
+			context("failure cases", func() {
+				context("when the source does not exist", func() {
+					it("returns an error", func() {
+						err := fs.Copy("no-such-source", destination)
+						Expect(err).To(MatchError(ContainSubstring("no such file or directory")))
+					})
+				})
+
+				context("when the source cannot be walked", func() {
+					it.Before(func() {
+						Expect(os.Chmod(source, 0000)).To(Succeed())
+					})
+
+					it.After(func() {
+						Expect(os.Chmod(source, 0777)).To(Succeed())
+					})
+
+					it("returns an error", func() {
+						err := fs.Copy(source, destination)
+						Expect(err).To(MatchError(ContainSubstring("permission denied")))
+					})
+				})
+			})
+		})
+	})
+}

fs/init_test.go

@@ -10,6 +10,7 @@ import (
 func TestUnitFS(t *testing.T) {
 	suite := spec.New("packit/fs", spec.Report(report.Terminal{}))
 	suite("Move", testMove)
+	suite("Copy", testCopy)
 	suite("IsEmptyDir", testIsEmptyDir)
 	suite("ChecksumCalculator", testChecksumCalculator)
 	suite.Run(t)