Fix bug: Exec task trims leading whitespace in ConsoleToMsBuild (#9722)

* fix bug Exec task trims leading whitespace in ConsoleToMsBuild

src/Tasks.UnitTests/Exec_Tests.cs

@@ -1033,6 +1033,25 @@ public void EndToEndMultilineExec_EscapeSpecialCharacters()
                 }
             }
         }
+
+        [Fact]
+        public void ConsoleOutputDoesNotTrimLeadingWhitespace()
+        {
+            string lineWithLeadingWhitespace = "    line with some leading whitespace";
+
+            using (var env = TestEnvironment.Create(_output))
+            {
+                var textFilePath = env.CreateFile("leading-whitespace.txt", lineWithLeadingWhitespace).Path;
+                Exec exec = PrepareExec(NativeMethodsShared.IsWindows ? $"type {textFilePath}" : $"cat {textFilePath}");
+                exec.ConsoleToMSBuild = true;
+
+                bool result = exec.Execute();
+
+                result.ShouldBeTrue();
+                exec.ConsoleOutput.Length.ShouldBe(1);
+                exec.ConsoleOutput[0].ItemSpec.ShouldBe(lineWithLeadingWhitespace);
+            }
+        }
     }
 
     internal sealed class ExecWrapper : Exec

src/Tasks/Exec.cs

@@ -410,7 +410,10 @@ protected override void LogEventsFromTextOutput(string singleLine, MessageImport
 
             if (ConsoleToMSBuild)
             {
-                string trimmedTextLine = singleLine.Trim();
+                string trimmedTextLine = ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave17_10) ?
+                    singleLine.TrimEnd() :
+                    singleLine.Trim();
+
                 if (trimmedTextLine.Length > 0)
                 {
                     // The lines read may be unescaped, so we need to escape them