Refactor and test PathContainsArchive

fs.go

@@ -919,15 +919,15 @@ var archiveExtensions = []string{
 	".tar.lz",
 }
 
-// FilepathContainsArchive returns true if the path contains an archive file (i.e.
+// PathContainsArchive returns true if the path contains an archive file (i.e.
 // whether the path traverses into an archive) solely by lexical analysis (no
 // reading of files or headers is performed). Such a path is not typically
-// usable by the OS, but can be used by the DeepFS type. Examples:
-// "/foo/example.zip/path/in/archive" or "C:\example.zip\path\in\archive"
-func FilepathContainsArchive(path string) bool {
-	pathPlusSep := path + string(filepath.Separator)
+// usable by the OS, but can be used by the DeepFS type. Slash must be the
+// path component separator. Example: "/foo/example.zip/path/in/archive"
+func PathContainsArchive(path string) bool {
+	pathPlusSep := path + "/"
 	for _, ext := range archiveExtensions {
-		if strings.Contains(pathPlusSep, ext+string(filepath.Separator)) {
+		if strings.Contains(pathPlusSep, ext+"/") {
 			return true
 		}
 	}

fs_test.go

@@ -104,6 +104,43 @@ func TestSplitPath(t *testing.T) {
 	}
 }
 
+func TestPathContainsArchive(t *testing.T) {
+	for i, testCase := range []struct {
+		input    string
+		expected bool
+	}{
+		{
+			input:    "",
+			expected: false,
+		},
+		{
+			input:    "foo",
+			expected: false,
+		},
+		{
+			input:    "foo.zip",
+			expected: true,
+		},
+		{
+			input:    "a/b/c.tar.gz",
+			expected: true,
+		},
+		{
+			input:    "a/b/c.tar.gz/d",
+			expected: true,
+		},
+		{
+			input:    "a/b/c.txt",
+			expected: false,
+		},
+	} {
+		actual := PathContainsArchive(testCase.input)
+		if actual != testCase.expected {
+			t.Errorf("Test %d (input=%q): expected %v but got %v", i, testCase.input, testCase.expected, actual)
+		}
+	}
+}
+
 var (
 	//go:embed testdata/test.zip
 	testZIP []byte