fs: Return ErrNotExist in ArchiveFS

Other minor fixes

archiver_test.go

@@ -113,30 +113,3 @@ func TestSkipList(t *testing.T) {
 		}
 	}
 }
-
-func TestPathWithoutTopDir(t *testing.T) {
-	for i, tc := range []struct {
-		input, expect string
-	}{
-		{
-			input:  "a/b/c",
-			expect: "b/c",
-		},
-		{
-			input:  "b/c",
-			expect: "c",
-		},
-		{
-			input:  "c",
-			expect: "",
-		},
-		{
-			input:  "",
-			expect: "",
-		},
-	} {
-		if actual := pathWithoutTopDir(tc.input); actual != tc.expect {
-			t.Errorf("Test %d (input=%s): Expected '%s' but got '%s'", i, tc.input, tc.expect, actual)
-		}
-	}
-}

fs.go

@@ -308,6 +308,9 @@ func (f ArchiveFS) Open(name string) (fs.File, error) {
 	if err != nil {
 		return nil, err
 	}
+	if fsFile == nil {
+		return nil, fs.ErrNotExist
+	}
 
 	return fsFile, nil
 }
@@ -472,7 +475,7 @@ func TopDirReadDir(fsys fs.ReadDirFS, name string) ([]fs.DirEntry, error) {
 func pathWithoutTopDir(fpath string) string {
 	slashIdx := strings.Index(fpath, "/")
 	if slashIdx < 0 {
-		return ""
+		return fpath
 	}
 	return fpath[slashIdx+1:]
 }

fs_test.go

@@ -0,0 +1,30 @@
+package archiver
+
+import "testing"
+
+func TestPathWithoutTopDir(t *testing.T) {
+	for i, tc := range []struct {
+		input, expect string
+	}{
+		{
+			input:  "a/b/c",
+			expect: "b/c",
+		},
+		{
+			input:  "b/c",
+			expect: "c",
+		},
+		{
+			input:  "c",
+			expect: "c",
+		},
+		{
+			input:  "",
+			expect: "",
+		},
+	} {
+		if actual := pathWithoutTopDir(tc.input); actual != tc.expect {
+			t.Errorf("Test %d (input=%s): Expected '%s' but got '%s'", i, tc.input, tc.expect, actual)
+		}
+	}
+}