Add more coverage for loader and strengthen type safety.

pkg/fs/confirmeddir.go

@@ -0,0 +1,58 @@
+package fs
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+// ConfirmedDir is a clean, absolute, delinkified path
+// that was confirmed to point to an existing directory.
+type ConfirmedDir string
+
+// HasPrefix returns true if the directory argument
+// is a prefix of self (d) from the point of view of
+// a file system.
+//
+// I.e., it's true if the argument equals or contains
+// self (d) in a file path sense.
+//
+// HasPrefix emulates the semantics of strings.HasPrefix
+// such that the following are true:
+//
+//   strings.HasPrefix("foobar", "foobar")
+//   strings.HasPrefix("foobar", "foo")
+//   strings.HasPrefix("foobar", "")
+//
+//   d := fSys.ConfirmDir("/foo/bar")
+//   d.HasPrefix("/foo/bar")
+//   d.HasPrefix("/foo")
+//   d.HasPrefix("/")
+//
+// Not contacting a file system here to check for
+// actual path existence.
+//
+// This is tested on linux, but will have trouble
+// on other operating systems.  As soon as related
+// work is completed in the core filepath package,
+// this code should be refactored to use it.
+// See:
+//   https://github.com/golang/go/issues/18355
+//   https://github.com/golang/dep/issues/296
+//   https://github.com/golang/dep/blob/master/internal/fs/fs.go#L33
+//   https://codereview.appspot.com/5712045
+func (d ConfirmedDir) HasPrefix(path ConfirmedDir) bool {
+	if path.String() == string(filepath.Separator) || path == d {
+		return true
+	}
+	return strings.HasPrefix(
+		string(d),
+		string(path)+string(filepath.Separator))
+}
+
+func (d ConfirmedDir) Join(path string) string {
+	return filepath.Join(string(d), path)
+}
+
+func (d ConfirmedDir) String() string {
+	return string(d)
+}

pkg/fs/confirmeddir_test.go

@@ -0,0 +1,87 @@
+package fs
+
+import (
+	"testing"
+)
+
+func TestJoin(t *testing.T) {
+	fSys := MakeFakeFS()
+	err := fSys.Mkdir("/foo")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	d, f, err := fSys.CleanedAbs("/foo")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if f != "" {
+		t.Fatalf("unexpected file: %v", f)
+	}
+	if d.Join("bar") != "/foo/bar" {
+		t.Fatalf("expected join %s", d.Join("bar"))
+	}
+}
+
+func TestHasPrefix_Slash(t *testing.T) {
+	d, f, err := MakeFakeFS().CleanedAbs("/")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if f != "" {
+		t.Fatalf("unexpected file: %v", f)
+	}
+	if d.HasPrefix("/hey") {
+		t.Fatalf("should be false")
+	}
+	if !d.HasPrefix("/") {
+		t.Fatalf("/ should have the prefix /")
+	}
+}
+
+func TestHasPrefix_SlashFoo(t *testing.T) {
+	fSys := MakeFakeFS()
+	err := fSys.Mkdir("/foo")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	d, _, err := fSys.CleanedAbs("/foo")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if d.HasPrefix("/fo") {
+		t.Fatalf("/foo does not have path prefix /fo")
+	}
+	if d.HasPrefix("/fod") {
+		t.Fatalf("/foo does not have path prefix /fod")
+	}
+	if !d.HasPrefix("/foo") {
+		t.Fatalf("/foo should have prefix /foo")
+	}
+}
+
+func TestHasPrefix_SlashFooBar(t *testing.T) {
+	fSys := MakeFakeFS()
+	err := fSys.MkdirAll("/foo/bar")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	d, _, err := fSys.CleanedAbs("/foo/bar")
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if d.HasPrefix("/fo") {
+		t.Fatalf("/foo/bar does not have path prefix /fo")
+	}
+	if d.HasPrefix("/foobar") {
+		t.Fatalf("/foo/bar does not have path prefix /foobar")
+	}
+	if !d.HasPrefix("/foo/bar") {
+		t.Fatalf("/foo/bar should have prefix /foo/bar")
+	}
+	if !d.HasPrefix("/foo") {
+		t.Fatalf("/foo/bar should have prefix /foo")
+	}
+	if !d.HasPrefix("/") {
+		t.Fatalf("/foo/bar should have prefix /")
+	}
+}

pkg/fs/fakefs.go

@@ -102,16 +102,16 @@ func (fs *fakeFs) Open(name string) (File, error) {
 	return fs.m[name], nil
 }
 
-// CleanedAbs does nothing and cannot fail.
-func (fs *fakeFs) CleanedAbs(path string) (string, string, error) {
+// CleanedAbs cannot fail.
+func (fs *fakeFs) CleanedAbs(path string) (ConfirmedDir, string, error) {
 	if fs.IsDir(path) {
-		return path, "", nil
+		return ConfirmedDir(path), "", nil
 	}
 	d := filepath.Dir(path)
 	if d == path {
-		return d, "", nil
+		return ConfirmedDir(d), "", nil
 	}
-	return d, filepath.Base(path), nil
+	return ConfirmedDir(d), filepath.Base(path), nil
 }
 
 // Exists returns true if file is known.

pkg/fs/fs.go

@@ -30,7 +30,7 @@ type FileSystem interface {
 	RemoveAll(name string) error
 	Open(name string) (File, error)
 	IsDir(name string) bool
-	CleanedAbs(path string) (string, string, error)
+	CleanedAbs(path string) (ConfirmedDir, string, error)
 	Exists(name string) bool
 	Glob(pattern string) ([]string, error)
 	ReadFile(name string) ([]byte, error)

pkg/fs/realfs.go

@@ -60,7 +60,8 @@ func (realFS) Open(name string) (File, error) { return os.Open(name) }
 // and file components.  If the entire path is
 // a directory, the file component is an empty
 // string.
-func (x realFS) CleanedAbs(path string) (string, string, error) {
+func (x realFS) CleanedAbs(
+	path string) (ConfirmedDir, string, error) {
 	absRoot, err := filepath.Abs(path)
 	if err != nil {
 		return "", "", fmt.Errorf(
@@ -72,7 +73,7 @@ func (x realFS) CleanedAbs(path string) (string, string, error) {
 			"evalsymlink failure on '%s' : %v", path, err)
 	}
 	if x.IsDir(deLinked) {
-		return deLinked, "", nil
+		return ConfirmedDir(deLinked), "", nil
 	}
 	d := filepath.Dir(deLinked)
 	if !x.IsDir(d) {
@@ -89,7 +90,7 @@ func (x realFS) CleanedAbs(path string) (string, string, error) {
 		log.Fatalf("these should be equal: '%s', '%s'",
 			filepath.Join(d, f), deLinked)
 	}
-	return d, f, nil
+	return ConfirmedDir(d), f, nil
 }
 
 // Exists returns true if os.Stat succeeds.

pkg/fs/realfs_test.go

@@ -52,7 +52,7 @@ func TestCleanedAbs_1(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected err=%v", err)
 	}
-	if d != wd {
+	if d.String() != wd {
 		t.Fatalf("unexpected d=%s", d)
 	}
 	if f != "" {
@@ -90,7 +90,7 @@ func TestCleanedAbs_3(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected err=%v", err)
 	}
-	if d != testDir {
+	if d.String() != testDir {
 		t.Fatalf("unexpected d=%s", d)
 	}
 	if f != "foo" {
@@ -119,7 +119,7 @@ func TestCleanedAbs_4(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected err=%v", err)
 	}
-	if d != filepath.Join(testDir, "d1", "d2") {
+	if d.String() != filepath.Join(testDir, "d1", "d2") {
 		t.Fatalf("unexpected d=%s", d)
 	}
 	if f != "" {
@@ -131,7 +131,7 @@ func TestCleanedAbs_4(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected err=%v", err)
 	}
-	if d != filepath.Join(testDir, "d1", "d2") {
+	if d.String() != filepath.Join(testDir, "d1", "d2") {
 		t.Fatalf("unexpected d=%s", d)
 	}
 	if f != "bar" {