echo: fix duplication of -- arguments

src/uu/echo/src/echo.rs

@@ -8,6 +8,7 @@ use clap::{Arg, ArgAction, ArgMatches, Command};
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::io::{self, StdoutLock, Write};
+use std::os::unix::ffi::OsStrExt;
 use uucore::error::{UResult, USimpleError};
 use uucore::format::{parse_escape_only, EscapedChar, FormatChar, OctalParsing};
 use uucore::{format_usage, help_about, help_section, help_usage};
@@ -28,11 +29,16 @@ mod options {
 fn handle_double_hyphens(args: impl uucore::Args) -> impl uucore::Args {
     let mut result = Vec::new();
     let mut is_first_double_hyphen = true;
-
-    for arg in args {
-        if arg == "--" && is_first_double_hyphen {
-            result.push(OsString::from("--"));
-            is_first_double_hyphen = false;
+    let mut option_index = 0;
+
+    for (i, arg) in args.enumerate() {
+        if is_first_double_hyphen {
+            if i < option_index + 2 && arg == "--" {
+                result.push(OsString::from("--"));
+                is_first_double_hyphen = false;
+            } else if arg.as_bytes()[0] == b'-' {
+                option_index = i
+            }
         }
         result.push(arg);
     }

tests/by-util/test_echo.rs

@@ -2,7 +2,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
-// spell-checker:ignore (words) araba merci
+// spell-checker:ignore (words) araba merci hehehe
 
 use crate::common::util::TestScenario;
 
@@ -243,7 +243,7 @@ fn test_hyphen_values_between() {
 }
 
 #[test]
-fn test_double_hyphens() {
+fn test_double_hyphens_at_start() {
     new_ucmd!().arg("--").succeeds().stdout_only("--\n");
     new_ucmd!()
         .arg("--")
@@ -252,6 +252,24 @@ fn test_double_hyphens() {
         .stdout_only("-- --\n");
 }
 
+#[test]
+fn test_double_hyphens_between() {
+    new_ucmd!()
+        .arg("a")
+        .arg("--")
+        .arg("b")
+        .succeeds()
+        .stdout_only("a -- b\n");
+
+    new_ucmd!()
+        .arg("foo ")
+        .arg("-- --")
+        .arg("bar")
+        .arg("hehehe")
+        .succeeds()
+        .stdout_only("foo  -- -- bar hehehe\n");
+}
+
 #[test]
 fn wrapping_octal() {
     // Some odd behavior of GNU. Values of \0400 and greater do not fit in the