[test_runner] Add detect-host command line flag

The --detect-host flag is provided as a convenience for running tests 
locally with named configurations. It alters the provided configurations
if needed to match the host system and architecture.

It is an error to use the flag without named configurations or as an 
option in the test_matrix.json file.

Add a the `Configuration._cloneHelper()` constructor with all parameters
as required arguments. This provides some compile time feedback when
new fields are added to the class and the clone methods haven't been 
updated.

Change-Id: I58e2ead1c3324c2cc893a4766d7daccd2787f631
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/280139
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>

pkg/smith/lib/configuration.dart

@@ -4,9 +4,9 @@
 import 'dart:io';
 
 // READ ME! If you add a new field to this, make sure to add it to
-// [parse()], [optionsEqual()], [hashCode], and [toString()]. A good check is to
-// comment out an existing field and see what breaks. Every error is a place
-// where you will need to add code for your new field.
+// [_cloneHelper()], [parse()], [optionsEqual()], [hashCode], and [toString()].
+// A good check is to comment out an existing field and see what breaks.
+// Every error is a place where you will need to add code for your new field.
 
 /// A set of options that affects how a Dart SDK test is run in a way that may
 /// affect its outcome.
@@ -210,6 +210,13 @@ class Configuration {
       return List<String>.from(value);
     }
 
+    var detectHost = boolOption('detect-host');
+    if (detectHost != null && detectHost) {
+      throw FormatException(
+          'The `detect-host` option is explicitly forbidden in the '
+          'test_matrix.json file.');
+    }
+
     // Extract options from the name and map.
     var architecture =
         enumOption("architecture", Architecture.names, Architecture.find);
@@ -393,6 +400,80 @@ class Configuration {
     }
   }
 
+  /// A helper constructor for cloning factories.
+  ///
+  /// NOTE: All parameters should be required to ensure that cloning factories
+  /// are updated when new class fields are added.
+  Configuration._cloneHelper(
+    this.name,
+    this.architecture,
+    this.compiler,
+    this.mode,
+    this.runtime,
+    this.system, {
+    required this.nnbdMode,
+    required this.sanitizer,
+    required this.babel,
+    required this.builderTag,
+    required this.genKernelOptions,
+    required this.vmOptions,
+    required this.dart2jsOptions,
+    required this.experiments,
+    required this.timeout,
+    required this.enableAsserts,
+    required this.isChecked,
+    required this.isCsp,
+    required this.isHostChecked,
+    required this.isMinified,
+    required this.useAnalyzerCfe,
+    required this.useAnalyzerFastaParser,
+    required this.useElf,
+    required this.useHotReload,
+    required this.useHotReloadRollback,
+    required this.useSdk,
+    required this.useQemu,
+  });
+
+  /// Creates a shallow clone of [source] with a new name and changes the system
+  /// and architecture to match the local host.
+  ///
+  /// NOTE: This calls [_cloneHelper] instead of the default constructor to
+  /// ensure it gets updated whenever new fields are added to the class.
+  factory Configuration.detectHost(Configuration source) =>
+      Configuration._cloneHelper(
+        '${source.name}-detect-host-${_detectHostNumber++}',
+        Architecture.host,
+        source.compiler,
+        source.mode,
+        source.runtime,
+        System.host,
+        nnbdMode: source.nnbdMode,
+        sanitizer: source.sanitizer,
+        babel: source.babel,
+        builderTag: source.builderTag,
+        genKernelOptions: source.genKernelOptions,
+        vmOptions: source.vmOptions,
+        dart2jsOptions: source.dart2jsOptions,
+        experiments: source.experiments,
+        timeout: source.timeout,
+        enableAsserts: source.enableAsserts,
+        isChecked: source.isChecked,
+        isCsp: source.isCsp,
+        isHostChecked: source.isHostChecked,
+        isMinified: source.isMinified,
+        useAnalyzerCfe: source.useAnalyzerCfe,
+        useAnalyzerFastaParser: source.useAnalyzerFastaParser,
+        useElf: source.useElf,
+        useHotReload: source.useHotReload,
+        useHotReloadRollback: source.useHotReloadRollback,
+        useSdk: source.useSdk,
+        useQemu: source.useQemu,
+      );
+
+  /// Counter to provide a unique number in the name of each call to
+  /// [detectHost].
+  static var _detectHostNumber = 1;
+
   /// Returns `true` if this configuration's options all have the same values
   /// as [other].
   bool optionsEqual(Configuration other) =>

pkg/test_runner/lib/src/options.dart

@@ -132,6 +132,12 @@ riscv32, riscv64, simriscv32, simriscv64''')
         hide: true,
         help: '''The named test configuration that supplies the values for all
 test options, specifying how tests should be run.''')
+    ..addFlag('detect-host',
+        aliases: ['detect_host'],
+        help: 'Replace the system and architecture options in named '
+            'configurations to match the local host. Provided only as a '
+            'convenience when running tests locally. It is an error use this '
+            'flag with without specifying a named configuration.')
     ..addFlag('build',
         help: 'Build the necessary targets to test this configuration')
     // TODO(sigmund): rename flag once we migrate all dart2js bots to the test
@@ -735,12 +741,32 @@ has been specified on the command line.''')
     }
 
     var namedConfigurations = data["named-configuration"] as List<String>;
+    var detectHost = data['detect-host'] as bool;
+    if (detectHost && namedConfigurations.isEmpty) {
+      _fail('The `--detect-host` flag is only supported for named '
+          'configurations.');
+    }
     if (namedConfigurations.isNotEmpty) {
       var testMatrix = TestMatrix.fromPath(_testMatrixFile);
       for (var namedConfiguration in namedConfigurations) {
         try {
           var configuration = testMatrix.configurations
               .singleWhere((c) => c.name == namedConfiguration);
+          if (configuration.system != System.host ||
+              configuration.architecture != Architecture.host) {
+            print("-- WARNING -- \n"
+                "The provided named configuration does not match the host "
+                "system or architecture:\n"
+                "    ${configuration.name}");
+            if (detectHost) {
+              configuration = Configuration.detectHost(configuration);
+              print("Detecting host configuration:\n"
+                  "    $configuration");
+            } else {
+              print("Passing the `--detect-host` flag will modify the named "
+                  "configuration to match the local system and architecture.");
+            }
+          }
           addConfiguration(configuration, namedConfiguration);
         } on StateError {
           var names = testMatrix.configurations