Made pipeline creation static for better Empty/standard ergonomics

Author: KathleenDollard

src/System.CommandLine.Subsystems.Tests/PipelineTests.cs

@@ -10,10 +10,7 @@ namespace System.CommandLine.Subsystems.Tests
     public class PipelineTests
     {
         private static Pipeline GetTestPipeline(VersionSubsystem versionSubsystem)
-            => new()
-            {
-                Version = versionSubsystem
-            };
+        => Pipeline.Create(version: versionSubsystem);
         private static CliConfiguration GetNewTestConfiguration()
         => new(new CliRootCommand { new CliOption<bool>("-x") }); // Add option expected by test data
 
@@ -156,7 +153,7 @@ public void Subsystem_runs_when_requested_even_when_there_are_errors(string inpu
         [Fact]
         public void Standard_pipeline_contains_expected_subsystems()
         {
-            var pipeline = new StandardPipeline();
+            var pipeline = Pipeline.Create();
             pipeline.Version.Should().BeOfType<VersionSubsystem>();
             pipeline.Help.Should().BeOfType<HelpSubsystem>();
             pipeline.ErrorReporting.Should().BeOfType<ErrorReportingSubsystem>();
@@ -166,7 +163,7 @@ public void Standard_pipeline_contains_expected_subsystems()
         [Fact]
         public void Normal_pipeline_contains_no_subsystems()
         {
-            var pipeline = new Pipeline();
+            var pipeline = Pipeline.CreateEmpty();;
             pipeline.Version.Should().BeNull();
             pipeline.Help.Should().BeNull();
             pipeline.ErrorReporting.Should().BeNull();
@@ -179,10 +176,8 @@ public void Subsystems_can_access_each_others_data()
             // TODO: Explore a mechanism that doesn't require the reference to retrieve data, this shows that it is awkward
             var symbol = new CliOption<bool>("-x");
             var console = GetNewTestConsole();
-            var pipeline = new StandardPipeline
-            {
-                Version = new AlternateSubsystems.VersionThatUsesHelpData(symbol)
-            };
+            var pipeline = Pipeline.Create(version : new AlternateSubsystems.VersionThatUsesHelpData(symbol));
+
             if (pipeline.Help is null) throw new InvalidOperationException();
             var rootCommand = new CliRootCommand
             {

src/System.CommandLine.Subsystems.Tests/VersionFunctionalTests.cs

@@ -19,7 +19,7 @@ public class VersionFunctionalTests
         public void When_the_version_option_is_specified_then_the_version_is_written_to_standard_out()
         {
             var configuration = new CliConfiguration(new CliRootCommand());
-            var pipeline = new Pipeline();
+            var pipeline = Pipeline.Create();
             var consoleHack = new ConsoleHack().RedirectToBuffer(true);
             pipeline.Version = new VersionSubsystem();
 

src/System.CommandLine.Subsystems.Tests/VersionSubsystemTests.cs

@@ -17,10 +17,7 @@ public void When_version_subsystem_is_used_the_version_option_is_added_to_the_ro
                 new CliOption<bool>("-x") // add option that is expected for the test data used here
             };
             var configuration = new CliConfiguration(rootCommand);
-            var pipeline = new Pipeline
-            {
-                Version = new VersionSubsystem()
-            };
+            var pipeline = Pipeline.Create(version: new VersionSubsystem());
 
             // Parse is used because directly calling Initialize would be unusual
             var result = pipeline.Parse(configuration, "");
@@ -98,10 +95,8 @@ public void Console_output_can_be_tested()
         public void Custom_version_subsystem_can_be_used()
         {
             var consoleHack = new ConsoleHack().RedirectToBuffer(true);
-            var pipeline = new Pipeline
-            {
-                Version = new AlternateSubsystems.AlternateVersion()
-            };
+            var pipeline = Pipeline.Create(version: new AlternateSubsystems.AlternateVersion());
+
             pipeline.Execute(new CliConfiguration(new CliRootCommand()), "-v", consoleHack);
             consoleHack.GetBuffer().Trim().Should().Be($"***{Constants.version}***");
         }
@@ -110,10 +105,8 @@ public void Custom_version_subsystem_can_be_used()
         public void Custom_version_subsystem_can_replace_standard()
         {
             var consoleHack = new ConsoleHack().RedirectToBuffer(true);
-            var pipeline = new StandardPipeline
-            {
-                Version = new AlternateSubsystems.AlternateVersion()
-            };
+            var pipeline = Pipeline.Create(version: new AlternateSubsystems.AlternateVersion());
+
             pipeline.Execute(new CliConfiguration(new CliRootCommand()), "-v", consoleHack);
             consoleHack.GetBuffer().Trim().Should().Be($"***{Constants.version}***");
         }

src/System.CommandLine.Subsystems/Pipeline.cs

@@ -9,11 +9,33 @@ namespace System.CommandLine;
 
 public class Pipeline
 {
+    public static Pipeline Create(HelpSubsystem? help = null,
+                                  VersionSubsystem? version = null,
+                                  CompletionSubsystem? completion = null,
+                                  DiagramSubsystem? diagram = null,
+                                  ErrorReportingSubsystem? errorReporting = null,
+                                  ValueSubsystem? value = null)
+        => new()
+        {
+            Help = help ?? new HelpSubsystem(),
+            Version = version ?? new VersionSubsystem(),
+            Completion = completion ?? new CompletionSubsystem(),
+            Diagram = diagram ?? new DiagramSubsystem(),
+            ErrorReporting = errorReporting ?? new ErrorReportingSubsystem(),
+            Value = value ?? new ValueSubsystem()
+        };
+
+    public static Pipeline CreateEmpty() 
+        => new();
+
+    private Pipeline() { }
+
     public HelpSubsystem? Help { get; set; }
     public VersionSubsystem? Version { get; set; }
     public CompletionSubsystem? Completion { get; set; }
     public DiagramSubsystem? Diagram { get; set; }
     public ErrorReportingSubsystem? ErrorReporting { get; set; }
+    public ValueSubsystem? Value { get; set; }
 
     public ParseResult Parse(CliConfiguration configuration, string rawInput)
         => Parse(configuration, CliParser.SplitCommandLine(rawInput).ToArray());

src/System.CommandLine.Subsystems/StandardPipeline.cs

@@ -7,7 +7,7 @@ public class PipelineContext(ParseResult? parseResult, string rawInput, Pipeline
 {
     public ParseResult? ParseResult { get; } = parseResult;
     public string RawInput { get; } = rawInput;
-    public Pipeline Pipeline { get; } = pipeline ?? new Pipeline();
+    public Pipeline Pipeline { get; } = pipeline ?? Pipeline.Create();
     public ConsoleHack ConsoleHack { get; } = consoleHack ?? new ConsoleHack();
 
     public bool AlreadyHandled { get; set; }