echo: fixed double hyphen as argument (#7581)

* Fixes #7558 Added check to only insert addition double hyphen if at start of arguments to correctly prepend addition hyphens for clap as well as additional test case

* additional comment

* fixes issue where flags precedes "--" as arguments

Author: cerdelen

src/uu/echo/src/echo.rs

@@ -23,18 +23,32 @@ mod options {
     pub const DISABLE_BACKSLASH_ESCAPE: &str = "disable_backslash_escape";
 }
 
+fn is_echo_flag(arg: &OsString) -> bool {
+    matches!(arg.to_str(), Some("-e" | "-E" | "-n"))
+}
+
 // A workaround because clap interprets the first '--' as a marker that a value
 // follows. In order to use '--' as a value, we have to inject an additional '--'
 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 is_first_argument = true;
+    let mut args_iter = args.into_iter();
+
+    if let Some(first_val) = args_iter.next() {
+        // the first argument ('echo') gets pushed before we start with the checks for flags/'--'
+        result.push(first_val);
+        // We need to skip any possible Flag arguments until we find the first argument to echo that
+        // is not a flag. If the first argument is double hyphen we inject an additional '--'
+        // otherwise we switch is_first_argument boolean to skip the checks for any further arguments
+        for arg in args_iter {
+            if is_first_argument && !is_echo_flag(&arg) {
+                is_first_argument = false;
+                if arg == "--" {
+                    result.push(OsString::from("--"));
+                }
+            }
+            result.push(arg);
         }
-        result.push(arg);
     }
 
     result.into_iter()

tests/by-util/test_echo.rs

@@ -242,6 +242,84 @@ fn test_hyphen_values_between() {
         .stdout_is("dumdum  dum dum dum -e dum\n");
 }
 
+#[test]
+fn test_double_hyphens_at_start() {
+    new_ucmd!().arg("--").succeeds().stdout_only("--\n");
+    new_ucmd!()
+        .arg("--")
+        .arg("--")
+        .succeeds()
+        .stdout_only("-- --\n");
+
+    new_ucmd!()
+        .arg("--")
+        .arg("a")
+        .succeeds()
+        .stdout_only("-- a\n");
+
+    new_ucmd!()
+        .arg("--")
+        .arg("a")
+        .arg("b")
+        .succeeds()
+        .stdout_only("-- a b\n");
+
+    new_ucmd!()
+        .arg("--")
+        .arg("a")
+        .arg("b")
+        .arg("--")
+        .succeeds()
+        .stdout_only("-- a b --\n");
+}
+
+#[test]
+fn test_double_hyphens_after_flags() {
+    new_ucmd!()
+        .arg("-e")
+        .arg("--")
+        .succeeds()
+        .stdout_only("--\n");
+
+    new_ucmd!()
+        .arg("-n")
+        .arg("-e")
+        .arg("--")
+        .arg("foo\n")
+        .succeeds()
+        .stdout_only("-- foo\n");
+
+    new_ucmd!()
+        .arg("-e")
+        .arg("--")
+        .arg("--")
+        .succeeds()
+        .stdout_only("-- --\n");
+
+    new_ucmd!()
+        .arg("-e")
+        .arg("--")
+        .arg("a")
+        .arg("--")
+        .succeeds()
+        .stdout_only("-- a --\n");
+
+    new_ucmd!()
+        .arg("-n")
+        .arg("--")
+        .arg("a")
+        .succeeds()
+        .stdout_only("-- a");
+
+    new_ucmd!()
+        .arg("-n")
+        .arg("--")
+        .arg("a")
+        .arg("--")
+        .succeeds()
+        .stdout_only("-- a --");
+}
+
 #[test]
 fn test_double_hyphens() {
     new_ucmd!().arg("--").succeeds().stdout_only("--\n");
@@ -250,6 +328,29 @@ fn test_double_hyphens() {
         .arg("--")
         .succeeds()
         .stdout_only("-- --\n");
+
+    new_ucmd!()
+        .arg("a")
+        .arg("--")
+        .arg("b")
+        .succeeds()
+        .stdout_only("a -- b\n");
+
+    new_ucmd!()
+        .arg("a")
+        .arg("--")
+        .arg("b")
+        .arg("--")
+        .succeeds()
+        .stdout_only("a -- b --\n");
+
+    new_ucmd!()
+        .arg("a")
+        .arg("b")
+        .arg("--")
+        .arg("--")
+        .succeeds()
+        .stdout_only("a b -- --\n");
 }
 
 #[test]