Fixing the incorrect error code even when CLI exits correctly (#1151)

## Why make this change?

- Closes #1150 
  - ErrorCode -1 is being returned when a command other than specified in dab is used, like --version, --help

## What is this change?

- Options `--help` generates `ErrorType.HelpRequestedError` and `ErrorType.HelpVerbRequestedError` while `--version` generates `ErrorType.VersionRequestedError`.
- While parsing we specifically looked if these error types are produced and marked them with exit code 0.

## How was this tested?

- [x] manually
- [x] unit tests

## Sample Request(s)
![image](https://user-images.githubusercontent.com/102276754/216330579-efe57e11-29e1-4302-8098-a68f35b7a499.png)

Author: abhishekkumams

src/Cli/src/Program.cs

@@ -35,6 +35,9 @@ public static int Main(string[] args)
             ConfigGenerator.SetLoggerForCliConfigGenerator(configGeneratorLogger);
             Utils.SetCliUtilsLogger(cliUtilsLogger);
 
+            // To know if `--help` or `--version` was requested.
+            bool isHelpOrVersionRequested = false;
+
             // Parsing user arguments and executing required methods.
             ParserResult<object>? result = parser.ParseArguments<InitOptions, AddOptions, UpdateOptions, StartOptions>(args)
                 .WithParsed<InitOptions>(options =>
@@ -100,9 +103,26 @@ public static int Main(string[] args)
                     {
                         cliLogger.LogError("Failed to start the engine.");
                     }
+                })
+                .WithNotParsed(err =>
+                {
+                    /// System.CommandLine considers --help and --version as NonParsed Errors
+                    /// ref: https://github.com/commandlineparser/commandline/issues/630
+                    /// This is a workaround to make sure our app exits with exit code 0,
+                    /// when user does --help or --versions.
+                    /// dab --help -> ErrorType.HelpVerbRequestedError
+                    /// dab [command-name] --help -> ErrorType.HelpRequestedError
+                    /// dab --version -> ErrorType.VersionRequestedError
+                    List<Error> errors = err.ToList();
+                    if (errors.Any(e => e.Tag == ErrorType.VersionRequestedError
+                                        || e.Tag == ErrorType.HelpRequestedError
+                                        || e.Tag == ErrorType.HelpVerbRequestedError))
+                    {
+                        isHelpOrVersionRequested = true;
+                    }
                 });
 
-            return result is Parsed<object> ? 0 : -1;
+            return ((result is Parsed<object>) || (isHelpOrVersionRequested)) ? 0 : -1;
         }
 
         /// <summary>

src/Cli/test/EndToEndTests.cs

@@ -472,6 +472,23 @@ public void TestEngineStartUpWithVerboseAndLogLevelOptions(string logLevelOption
         Assert.IsTrue(output.Contains($"User provided config file: {_testRuntimeConfig}"));
     }
 
+    /// <summary>
+    /// Test to verify that `--help` and `--version` along with know command/option produce the exit code 0,
+    /// while unknown commands/options have exit code -1.
+    /// </summary>
+    [DataTestMethod]
+    [DataRow(new string[] { "--version" }, 0, DisplayName = "Checking version should have exit code 0.")]
+    [DataRow(new string[] { "--help" }, 0, DisplayName = "Checking commands with help should have exit code 0.")]
+    [DataRow(new string[] { "add", "--help" }, 0, DisplayName = "Checking options with help should have exit code 0.")]
+    [DataRow(new string[] { "initialize" }, -1, DisplayName = "Invalid Command should have exit code -1.")]
+    [DataRow(new string[] { "init", "--database-name", "mssql" }, -1, DisplayName = "Invalid Options should have exit code -1.")]
+    [DataRow(new string[] { "init", "--database-type", "mssql", "-c", "dab-config-test.json" }, 0,
+        DisplayName = "Correct command with correct options should have exit code 0.")]
+    public void VerifyExitCodeForCli(string[] cliArguments, int expectedErrorCode)
+    {
+        Assert.AreEqual(Cli.Program.Main(cliArguments), expectedErrorCode);
+    }
+
     /// <summary>
     /// Test to verify that help writer window generates output on the console.
     /// </summary>