Make Environment.GetCommandLineArgs() work on Project N. (#3894)

3 files changed, 57 insertions, 34 deletions

diff --git a/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.ProjectN.cs b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.ProjectN.cs
index f0fbc7b20..f49f9cf92 100644
--- a/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.ProjectN.cs
+++ b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.ProjectN.cs
@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Runtime;
 
 namespace Internal.Runtime.Augments
 {
@@ -15,9 +16,6 @@ namespace Internal.Runtime.Augments
             throw new PlatformNotSupportedException();
         }
 
-        public static string[] GetCommandLineArgs()
-        {
-            throw new PlatformNotSupportedException(SR.PlatformNotSupported_GetCommandLineArgs);
-        }
+        public static string[] GetCommandLineArgs() => CommandLine.InternalCreateCommandLine(includeArg0: true);
     }
 }
diff --git a/src/System.Private.CoreLib/src/Resources/Strings.resx b/src/System.Private.CoreLib/src/Resources/Strings.resx
index 9e8c957ee..53a8ed147 100644
--- a/src/System.Private.CoreLib/src/Resources/Strings.resx
+++ b/src/System.Private.CoreLib/src/Resources/Strings.resx
@@ -2449,7 +2449,4 @@
   <data name="Arg_OpenType" xml:space="preserve">
     <value>Cannot create an instance of {0} as it is an open type.</value>
   </data>
-  <data name="PlatformNotSupported_GetCommandLineArgs" xml:space="preserve">
-    <value>Environment.GetCommandLineArgs() is not supported on this platform.</value>
-  </data>
 </root>
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CommandLine.Windows.cs b/src/System.Private.CoreLib/src/System/Runtime/CommandLine.Windows.cs
index 73ffd6af6..6b018375e 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/CommandLine.Windows.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/CommandLine.Windows.cs
@@ -20,16 +20,17 @@ namespace System.Runtime
             string[] commandLine = InternalCreateCommandLine();
             return RawCalliHelper.Call<int>(pfnUserMain, commandLine);
         }
-        
+
         [RuntimeExport("CreateCommandLine")]
-        public static unsafe string[] InternalCreateCommandLine()
-        {
-            char * pCmdLine = Interop.mincore.GetCommandLine();
+        public static string[] InternalCreateCommandLine() => InternalCreateCommandLine(includeArg0: false);
 
-            int nArgs = SegmentCommandLine(pCmdLine, null);
+        internal static unsafe string[] InternalCreateCommandLine(bool includeArg0)
+        {
+            char* pCmdLine = Interop.mincore.GetCommandLine();
+            int nArgs = SegmentCommandLine(pCmdLine, null, includeArg0);
 
             string[] argArray = new string[nArgs];
-            SegmentCommandLine(pCmdLine, argArray);
+            SegmentCommandLine(pCmdLine, argArray, includeArg0);
             return argArray;
         }
 
@@ -40,37 +41,32 @@ namespace System.Runtime
         //
         // This functions interface mimics the CommandLineToArgvW api.
         //
-        private static unsafe int SegmentCommandLine(char * pCmdLine, string[] argArray)
+        private static unsafe int SegmentCommandLine(char * pCmdLine, string[] argArray, bool includeArg0)
         {
             int nArgs = 0;
-            char c;
-            bool inquote;
-
-            // First, parse the program name (argv[0]). Argv[0] is parsed under special rules. Anything up to 
-            // the first whitespace outside a quoted subtring is accepted. Backslashes are treated as normal 
-            // characters.
 
             char* psrc = pCmdLine;
 
-            inquote = false;
-            do
             {
-                if (*psrc == '"')
+                // First, parse the program name (argv[0]). Argv[0] is parsed under special rules. Anything up to 
+                // the first whitespace outside a quoted subtring is accepted. Backslashes are treated as normal 
+                // characters.
+                char* psrcOrig = psrc;
+
+                int arg0Len = ScanArgument0(ref psrc, null);
+                if (includeArg0)
                 {
-                    inquote = !inquote;
-                    c = *psrc++;
-                    continue;
+                    if (argArray != null)
+                    {
+                        char[] arg0 = new char[arg0Len];
+                        ScanArgument0(ref psrcOrig, arg0);
+                        argArray[nArgs] = new string(arg0);
+                    }
+                    nArgs++;
                 }
-
-                c = *psrc++;
-            } while ((c != '\0' && (inquote || (c != ' ' && c != '\t'))));
-
-            if (c == '\0')
-            {
-                psrc--;
             }
 
-            inquote = false;
+            bool inquote = false;
 
             // loop on each argument
             for (;;)
@@ -106,6 +102,38 @@ namespace System.Runtime
             return nArgs;
         }
 
+        private static unsafe int ScanArgument0(ref char* psrc, char[] arg)
+        {
+            // Argv[0] is parsed under special rules. Anything up to 
+            // the first whitespace outside a quoted subtring is accepted. Backslashes are treated as normal 
+            // characters.
+            int charIdx = 0;
+            bool inquote = false;
+            for (;;)
+            {
+                char c = *psrc++;
+                if (c == '"')
+                {
+                    inquote = !inquote;
+                    continue;
+                }
+
+                if (c == '\0' || (!inquote && (c == ' ' || c == '\t')))
+                {
+                    psrc--;
+                    break;
+                }
+
+                if (arg != null)
+                {
+                    arg[charIdx] = c;
+                }
+                charIdx++;
+            }
+
+            return charIdx;
+        }
+
         private static unsafe int ScanArgument(ref char* psrc, ref bool inquote, char[] arg)
         {
             int charIdx = 0;