Resolve symbolic links for app dir

build.go

@@ -169,19 +169,32 @@ func (c *Client) validateImageReference(imageName string) (name.Reference, error
 }
 
 func (c *Client) processAppDir(appDir string) (string, error) {
+	var (
+		resolvedAppDir = appDir
+		err            error
+	)
+
 	if appDir == "" {
-		var err error
-		appDir, err = os.Getwd()
-		if err != nil {
+		if appDir, err = os.Getwd(); err != nil {
 			return "", err
 		}
 	}
-	if fi, err := os.Stat(appDir); err != nil {
+
+	if resolvedAppDir, err = filepath.EvalSymlinks(appDir); err != nil {
+		return "", err
+	}
+
+	if resolvedAppDir, err = filepath.Abs(resolvedAppDir); err != nil {
+		return "", err
+	}
+
+	if fi, err := os.Stat(resolvedAppDir); err != nil {
 		return "", err
 	} else if !fi.IsDir() {
 		return "", fmt.Errorf("%s is not a directory", appDir)
 	}
-	return filepath.Abs(appDir)
+
+	return resolvedAppDir, nil
 }
 
 func (c *Client) processBuildpacks(buildpacks []string) ([]buildpack.Buildpack, builder.GroupMetadata, error) {

build_test.go

@@ -185,6 +185,75 @@ func testBuild(t *testing.T, when spec.G, it spec.S) {
 				h.AssertNil(t, err)
 				h.AssertEq(t, fakeLifecycle.Opts.AppDir, absPath)
 			})
+
+			when("appDir is a symlink", func() {
+				var (
+					appDirName     = "some-app"
+					absoluteAppDir string
+					tmpDir         string
+					err            error
+				)
+
+				it.Before(func() {
+					tmpDir, err = ioutil.TempDir("", "build-symlink-test")
+					h.AssertNil(t, err)
+
+					appDirPath := filepath.Join(tmpDir, appDirName)
+					h.AssertNil(t, os.MkdirAll(filepath.Join(tmpDir, appDirName), 0666))
+
+					absoluteAppDir, err = filepath.Abs(appDirPath)
+					h.AssertNil(t, err)
+
+					absoluteAppDir, err = filepath.EvalSymlinks(appDirPath)
+					h.AssertNil(t, err)
+				})
+
+				it.After(func() {
+					_ = os.RemoveAll(tmpDir)
+				})
+
+				it("resolves relative symbolic links", func() {
+					relLink := filepath.Join(tmpDir, "some-app.link")
+					h.AssertNil(t, os.Symlink(filepath.Join(".", appDirName), relLink))
+
+					h.AssertNil(t, subject.Build(context.TODO(), BuildOptions{
+						Image:  "some/app",
+						AppDir: relLink,
+					}))
+
+					h.AssertEq(t, fakeLifecycle.Opts.AppDir, absoluteAppDir)
+				})
+
+				it("resolves absolute symbolic links", func() {
+					relLink := filepath.Join(tmpDir, "some-app.link")
+					h.AssertNil(t, os.Symlink(absoluteAppDir, relLink))
+
+					h.AssertNil(t, subject.Build(context.TODO(), BuildOptions{
+						Image:  "some/app",
+						AppDir: relLink,
+					}))
+
+					h.AssertEq(t, fakeLifecycle.Opts.AppDir, absoluteAppDir)
+				})
+
+				it("resolves symbolic links recursively", func() {
+					linkRef1 := absoluteAppDir
+					absoluteLink1 := filepath.Join(tmpDir, "some-app-abs-1.link")
+
+					linkRef2 := "some-app-abs-1.link"
+					symbolicLink := filepath.Join(tmpDir, "some-app-rel-2.link")
+
+					h.AssertNil(t, os.Symlink(linkRef1, absoluteLink1))
+					h.AssertNil(t, os.Symlink(linkRef2, symbolicLink))
+
+					h.AssertNil(t, subject.Build(context.TODO(), BuildOptions{
+						Image:  "some/app",
+						AppDir: symbolicLink,
+					}))
+
+					h.AssertEq(t, fakeLifecycle.Opts.AppDir, absoluteAppDir)
+				})
+			})
 		})
 
 		when("Builder option", func() {