id: Don't treat unresolved IDs as error by default

.github/workflows/make.yml

@@ -5,7 +5,7 @@ name: make
 # spell-checker:ignore (jargon) deps softprops toolchain
 # spell-checker:ignore (people) dawidd
 # spell-checker:ignore (shell/tools) nextest sccache zstd
-# spell-checker:ignore (misc) bindir busytest defconfig DESTDIR manpages multisize runtest testsuite toybox uutils
+# spell-checker:ignore (misc) bindir busytest defconfig DESTDIR manpages multisize runtest testsuite toybox userns uutils
 
 env:
   PROJECT_NAME: coreutils
@@ -80,7 +80,11 @@ jobs:
         mv -t target/ target.cache/release 2>/dev/null || true
     - name: "`make nextest`"
       shell: bash
-      run: make nextest PROFILE=ci CARGOFLAGS="--hide-progress-bar"
+      run: |
+        # some test needs unshare
+        sudo sysctl -w kernel.unprivileged_userns_clone=1 || true
+        sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0 || true
+        make nextest PROFILE=ci CARGOFLAGS="--hide-progress-bar"
       env:
         RUST_BACKTRACE: "1"
     - name: Upload test results to Codecov

src/uu/id/src/id.rs

@@ -641,54 +641,26 @@ fn id_print(state: &State, groups: &[u32]) -> io::Result<()> {
     write!(
         lock,
         "uid={uid}({})",
-        entries::uid2usr(uid).unwrap_or_else(|_| {
-            show_error!(
-                "{}",
-                translate!("id-error-cannot-find-user-name", "uid" => uid)
-            );
-            set_exit_code(1);
-            uid.to_string()
-        })
+        entries::uid2usr(uid).unwrap_or_else(|_| { uid.to_string() })
     )?;
     write!(
         lock,
         " gid={gid}({})",
-        entries::gid2grp(gid).unwrap_or_else(|_| {
-            show_error!(
-                "{}",
-                translate!("id-error-cannot-find-group-name", "gid" => gid)
-            );
-            set_exit_code(1);
-            gid.to_string()
-        })
+        entries::gid2grp(gid).unwrap_or_else(|_| { gid.to_string() })
     )?;
     if !state.user_specified && (euid != uid) {
         write!(
             lock,
             " euid={euid}({})",
-            entries::uid2usr(euid).unwrap_or_else(|_| {
-                show_error!(
-                    "{}",
-                    translate!("id-error-cannot-find-user-name", "uid" => euid)
-                );
-                set_exit_code(1);
-                euid.to_string()
-            })
+            entries::uid2usr(euid).unwrap_or_else(|_| { euid.to_string() })
         )?;
     }
     if !state.user_specified && (egid != gid) {
         // BUG?  printing egid={euid} ?
         write!(
             lock,
             " egid={egid}({})",
-            entries::gid2grp(egid).unwrap_or_else(|_| {
-                show_error!(
-                    "{}",
-                    translate!("id-error-cannot-find-group-name", "gid" => egid)
-                );
-                set_exit_code(1);
-                egid.to_string()
-            })
+            entries::gid2grp(egid).unwrap_or_else(|_| { egid.to_string() })
         )?;
     }
     write!(
@@ -698,14 +670,7 @@ fn id_print(state: &State, groups: &[u32]) -> io::Result<()> {
             .iter()
             .map(|&gr| format!(
                 "{gr}({})",
-                entries::gid2grp(gr).unwrap_or_else(|_| {
-                    show_error!(
-                        "{}",
-                        translate!("id-error-cannot-find-group-name", "gid" => gr)
-                    );
-                    set_exit_code(1);
-                    gr.to_string()
-                })
+                entries::gid2grp(gr).unwrap_or_else(|_| { gr.to_string() })
             ))
             .collect::<Vec<_>>()
             .join(",")

tests/by-util/test_id.rs

@@ -51,6 +51,35 @@ fn test_id_no_specified_user() {
         .code_is(exp_result.code());
 }
 
+#[test]
+#[cfg(target_os = "linux")]
+fn test_id_nonexisting_ids() {
+    use uutests::{get_tests_binary, util::unshare_bin};
+
+    let unshare = unwrap_or_return!(unshare_bin());
+
+    let unshare_args = ["-U", "--map-user=10101", "--"];
+
+    let exp_result = Command::new(&unshare)
+        .args(unshare_args)
+        .arg(util_name!())
+        .output()
+        .unwrap();
+
+    let result = Command::new(unshare)
+        .args(unshare_args)
+        .arg(get_tests_binary!())
+        .arg(util_name!())
+        .output()
+        .unwrap();
+
+    assert_eq!(result.status.code(), exp_result.status.code());
+
+    let exp_stderr = String::from_utf8_lossy(&exp_result.stderr);
+    let act_stderr = String::from_utf8_lossy(&result.stderr);
+    assert_eq!(act_stderr, exp_stderr);
+}
+
 #[test]
 fn test_id_single_user() {
     let test_users = [&whoami()[..]];

tests/uutests/src/lib/util.rs

@@ -3235,6 +3235,38 @@ pub fn run_ucmd_as_root_with_stdin_stdout(
     }
 }
 
+/// Determines whether `unshare` can be used in the current setup, and returns the path to its binary.
+///
+/// # Errors
+/// If `unshare` is not available on the system, or cannot be run (e.g. in CI), this function
+/// returns a String describing the reason.
+pub fn unshare_bin() -> Result<String> {
+    // Determine whether 'unshare' is available
+    let which_result = Command::new("which").arg("unshare").output()?;
+    if !which_result.status.success() {
+        return Err(io::Error::other("'unshare' not found on system"));
+    }
+    let unshare = String::from_utf8_lossy(&which_result.stdout)
+        .trim()
+        .to_string();
+
+    // Determine whether 'unshare' works as expected
+    let test_result = Command::new(&unshare)
+        .args(["-U", "--map-user=0", "--map-group=0", "--", "whoami"])
+        .output()?;
+    if !test_result.status.success() {
+        let err = String::from_utf8_lossy(&test_result.stderr)
+            .trim()
+            .to_string();
+        return Err(io::Error::other(format!("failed to run 'unshare': {err}")));
+    }
+    if String::from_utf8_lossy(&test_result.stdout).trim() != "root" {
+        return Err(io::Error::other("'unshare' does not work as expected"));
+    }
+
+    Ok(unshare)
+}
+
 /// Sanity checks for test utils
 #[cfg(test)]
 mod tests {