KeyChar should be preserved for Ctrl+Letter (#75853)

Author: adamsitnik

src/libraries/System.Console/src/System/IO/KeyParser.cs

@@ -333,7 +333,7 @@ private static ConsoleKeyInfo ParseFromSingleChar(char single, bool isAlt)
             _ when char.IsAsciiLetterLower(single) => ConsoleKey.A + single - 'a',
             _ when char.IsAsciiLetterUpper(single) => UppercaseCharacter(single, out isShift),
             _ when char.IsAsciiDigit(single) => ConsoleKey.D0 + single - '0', // We can't distinguish DX and Ctrl+DX as they produce same values. Limitation: Ctrl+DX can't be mapped.
-            _ when char.IsBetween(single, (char)1, (char)26) => ControlAndLetterPressed(single, out keyChar, out isCtrl),
+            _ when char.IsBetween(single, (char)1, (char)26) => ControlAndLetterPressed(single, isAlt, out keyChar, out isCtrl),
             _ when char.IsBetween(single, (char)28, (char)31) => ControlAndDigitPressed(single, out keyChar, out isCtrl),
             '\u0000' => ControlAndDigitPressed(single, out keyChar, out isCtrl),
             _ => default
@@ -359,7 +359,7 @@ static ConsoleKey UppercaseCharacter(char single, out bool isShift)
             return ConsoleKey.A + single - 'A';
         }
 
-        static ConsoleKey ControlAndLetterPressed(char single, out char keyChar, out bool isCtrl)
+        static ConsoleKey ControlAndLetterPressed(char single, bool isAlt, out char keyChar, out bool isCtrl)
         {
             // Ctrl+(a-z) characters are mapped to values from 1 to 26.
             // Ctrl+H is mapped to 8, which also maps to Ctrl+Backspace.
@@ -370,7 +370,9 @@ static ConsoleKey ControlAndLetterPressed(char single, out char keyChar, out boo
             Debug.Assert(single != 'b' && single != '\t' && single != '\n' && single != '\r');
 
             isCtrl = true;
-            keyChar = default; // we could use the letter here, but it's impossible to distinguish upper vs lowercase (and Windows doesn't do it as well)
+            // Preserve the original character the same way Windows does (#75795),
+            // but only when Alt was not pressed at the same time.
+            keyChar = isAlt ? default : single;
             return ConsoleKey.A + single - 1;
         }
 

src/libraries/System.Console/tests/KeyParserTests.cs

@@ -264,6 +264,8 @@ public void ExtendedStringCodePath()
     {
         get
         {
+            // Control+C
+            yield return (new string((char)3, 1), new[] { new ConsoleKeyInfo((char)3, ConsoleKey.C, false, false, true) });
             // Backspace
             yield return (new string((char)127, 1), new[] { new ConsoleKeyInfo((char)127, ConsoleKey.Backspace, false, false, false) });
             // Ctrl+Backspace
@@ -448,7 +450,7 @@ public class GNOMETerminalData : TerminalData
         {
             yield return (new byte[] { 90 }, new ConsoleKeyInfo('Z', ConsoleKey.Z, true, false, false));
             yield return (new byte[] { 97 }, new ConsoleKeyInfo('a', ConsoleKey.A, false, false, false));
-            yield return (new byte[] { 1 }, new ConsoleKeyInfo(default, ConsoleKey.A, false, false, true));
+            yield return (new byte[] { 1 }, new ConsoleKeyInfo((char)1, ConsoleKey.A, false, false, true));
             yield return (new byte[] { 27, 97 }, new ConsoleKeyInfo('a', ConsoleKey.A, false, true, false));
             yield return (new byte[] { 27, 1 }, new ConsoleKeyInfo(default, ConsoleKey.A, false, true, true));
             yield return (new byte[] { 49 }, new ConsoleKeyInfo('1', ConsoleKey.D1, false, false, false));
@@ -613,7 +615,7 @@ public class XTermData : TerminalData
         {
             yield return (new byte[] { 90 }, new ConsoleKeyInfo('Z', ConsoleKey.Z, true, false, false));
             yield return (new byte[] { 97 }, new ConsoleKeyInfo('a', ConsoleKey.A, false, false, false));
-            yield return (new byte[] { 1 }, new ConsoleKeyInfo(default, ConsoleKey.A, false, false, true));
+            yield return (new byte[] { 1 }, new ConsoleKeyInfo((char)1, ConsoleKey.A, false, false, true));
             yield return (new byte[] { 195, 161 }, new ConsoleKeyInfo('\u00E1', default, false, false, false));
             yield return (new byte[] { 194, 129 }, new ConsoleKeyInfo('\u0081', default, false, false, false));
             yield return (new byte[] { 49 }, new ConsoleKeyInfo('1', ConsoleKey.D1, false, false, false));
@@ -886,7 +888,7 @@ public class WindowsTerminalData : TerminalData
         {
             yield return (new byte[] { 90 }, new ConsoleKeyInfo('Z', ConsoleKey.Z, true, false, false));
             yield return (new byte[] { 97 }, new ConsoleKeyInfo('a', ConsoleKey.A, false, false, false));
-            yield return (new byte[] { 1 }, new ConsoleKeyInfo(default, ConsoleKey.A, false, false, true));
+            yield return (new byte[] { 1 }, new ConsoleKeyInfo((char)1, ConsoleKey.A, false, false, true));
             yield return (new byte[] { 27, 97 }, new ConsoleKeyInfo('a', ConsoleKey.A, false, true, false));
             yield return (new byte[] { 27, 1 }, new ConsoleKeyInfo(default, ConsoleKey.A, false, true, true));
             yield return (new byte[] { 49 }, new ConsoleKeyInfo('1', ConsoleKey.D1, false, false, false));