Fix issue #12013 - not allow mixed dash and slash in command line parameter prefix (#15142)

src/Microsoft.PowerShell.ConsoleHost/host/msh/CommandLineParameterParser.cs

@@ -608,7 +608,8 @@ namespace Microsoft.PowerShell
                 return (switchKey: string.Empty, shouldBreak: false);
             }
 
-            if (!CharExtensions.IsDash(switchKey[0]) && switchKey[0] != '/')
+            char firstChar = switchKey[0];
+            if (!CharExtensions.IsDash(firstChar) && firstChar != '/')
             {
                 // then it's a file
                 --argIndex;
@@ -622,7 +623,7 @@ namespace Microsoft.PowerShell
             switchKey = switchKey.Substring(1);
 
             // chop off the second dash so we're agnostic wrt specifying - or --
-            if (!string.IsNullOrEmpty(switchKey) && CharExtensions.IsDash(switchKey[0]))
+            if (!string.IsNullOrEmpty(switchKey) && CharExtensions.IsDash(firstChar) && switchKey[0] == firstChar)
             {
                 switchKey = switchKey.Substring(1);
             }

test/xUnit/csharp/test_CommandLineParser.cs

@@ -143,6 +143,47 @@ namespace PSTests.Parallel
             Assert.Contains("-noprofile", cpp.ErrorMessage);
         }
 
+        [Theory]
+        [InlineData("-Version")]
+        [InlineData("--Version")]
+        [InlineData("/Version")]
+        public static void TestParameter_Dash_Or_Slash(params string[] commandLine)
+        {
+            var cpp = new CommandLineParameterParser();
+
+            cpp.Parse(commandLine);
+
+            Assert.False(cpp.AbortStartup);
+            Assert.False(cpp.NoExit);
+            Assert.True(cpp.NonInteractive);
+            Assert.False(cpp.ShowBanner);
+            Assert.False(cpp.ShowShortHelp);
+            Assert.False(cpp.NoPrompt);
+            Assert.True(cpp.ShowVersion);
+            Assert.True(cpp.SkipProfiles);
+            Assert.Null(cpp.ErrorMessage);
+        }
+
+        [Theory]
+        [InlineData("/-Version")]
+        [InlineData("-/Version")]
+        public static void TestParameter_Wrong_Dash_And_Slash(params string[] commandLine)
+        {
+            var cpp = new CommandLineParameterParser();
+
+            cpp.Parse(commandLine);
+
+            Assert.True(cpp.AbortStartup);
+            Assert.False(cpp.NoExit);
+            Assert.False(cpp.NonInteractive);
+            Assert.False(cpp.ShowBanner);
+            Assert.True(cpp.ShowShortHelp);
+            Assert.False(cpp.NoPrompt);
+            Assert.False(cpp.ShowVersion);
+            Assert.False(cpp.SkipProfiles);
+            Assert.Contains(commandLine[0], cpp.ErrorMessage);
+        }
+
         [Theory]
         [InlineData("-Version")]
         [InlineData("-V")]