ls: fall back to "." metadata for ".." on WASI (#11633)

* ls: fall back to "." metadata for ".." on WASI

On WASI the sandbox blocks access to the parent directory at the
preopened root, causing ls -a to show an error and display ".."
with question marks. Fall back to the current directory metadata
so the entry appears with valid information.

.vscode/cspell.dictionaries/jargon.wordlist.txt

@@ -219,6 +219,9 @@ nofield
 dtolnay
 Swatinem
 
+preopened
+dotdot
+
 # * clippy
 uninlined
 nonminimal

src/uu/ls/src/ls.rs

@@ -1265,7 +1265,19 @@ fn depth_first_list(
                 false,
             ),
             PathData::new(
-                path_data.path().join("..").into(),
+                // On WASI the sandbox may block access to ".." at the
+                // preopened root.  Fall back to "." so the entry still
+                // appears with valid metadata instead of an error.
+                {
+                    let dotdot = path_data.path().join("..");
+                    #[cfg(target_os = "wasi")]
+                    let dotdot = if dotdot.metadata().is_err() {
+                        path_data.path().into()
+                    } else {
+                        dotdot
+                    };
+                    dotdot.into()
+                },
                 None,
                 Some(OsStr::new("..").into()),
                 config,

tests/by-util/test_ls.rs

@@ -7133,3 +7133,18 @@ fn test_ls_non_utf8_hidden() {
 
     scene.ucmd().succeeds().stdout_does_not_contain(".hidden");
 }
+
+#[test]
+#[cfg(target_os = "wasi")]
+fn test_ls_a_dotdot_no_error_on_wasi() {
+    // On WASI the sandbox may block access to ".." at the preopened root.
+    // ls -a should still succeed and show ".." without an error message.
+    let scene = TestScenario::new(util_name!());
+    scene
+        .ucmd()
+        .arg("-a")
+        .arg("-1")
+        .succeeds()
+        .stdout_contains("..")
+        .no_stderr();
+}