Replace the configuration map with a typed object.

tools/testing/dart/environment.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'configuration.dart';
+
+typedef String _LookUpFunction(Configuration configuration);
+typedef bool _BoolLookUpFunction(Configuration configuration);
+
+// TODO(29756): Instead of synthesized negated variables like "unchecked",
+// consider adding support for "!" to status expressions.
+final _variables = {
+  "analyzer": new _Variable.bool((c) => c.compiler == Compiler.dart2analyzer),
+  "arch": new _Variable((c) => c.architecture.name, Architecture.names),
+  "browser": new _Variable.bool((c) => c.runtime.isBrowser),
+  "builder_tag": new _Variable((c) => c.builderTag ?? "", const []),
+  "checked": new _Variable.bool((c) => c.isChecked),
+  "compiler": new _Variable((c) => c.compiler.name, Compiler.names),
+  "csp": new _Variable.bool((c) => c.isCsp),
+  "dart2js_with_kernel": new _Variable.bool((c) => c.useDart2JSWithKernel),
+  "fast_startup": new _Variable.bool((c) => c.useFastStartup),
+  "host_checked": new _Variable.bool((c) => c.isHostChecked),
+  "host_unchecked": new _Variable.bool((c) => !c.isHostChecked),
+  "hot_reload": new _Variable.bool((c) => c.hotReload),
+  "hot_reload_rollback": new _Variable.bool((c) => c.hotReloadRollback),
+  "ie": new _Variable.bool((c) => c.runtime.isIE),
+  "jscl": new _Variable.bool((c) => c.runtime.isJSCommandLine),
+  "minified": new _Variable.bool((c) => c.isMinified),
+  "mode": new _Variable((c) => c.mode.name, Mode.names),
+  "runtime": new _Variable((c) => c.runtime.name, Runtime.names),
+  "strong": new _Variable.bool((c) => c.isStrong),
+  "system": new _Variable((c) => c.system.name, System.names),
+  "unchecked": new _Variable.bool((c) => !c.isChecked),
+  "unminified": new _Variable.bool((c) => !c.isMinified),
+  "use_sdk": new _Variable.bool((c) => c.useSdk)
+};
+
+/// Defines the variables that are available for use inside a status file
+/// section header.
+///
+/// These mostly map to command line arguments with the same name, though this
+/// is only a subset of the full set of command line arguments.
+class Environment {
+  /// Validates that the variable with [name] exists and can be compared
+  /// against [value].
+  ///
+  /// If any errors are found, adds them to [errors].
+  static void validate(String name, String value, List<String> errors) {
+    var variable = _variables[name];
+    if (variable == null) {
+      errors.add('Unknown variable "$name".');
+      return;
+    }
+
+    // The "builder_tag" variable doesn't have an enumerated set of values.
+    if (variable.allowedValues.isEmpty) return;
+
+    if (!variable.allowedValues.contains(value)) {
+      errors.add(
+          'Variable "$name" cannot have value "$value". Allowed values are:\n' +
+              variable.allowedValues.join(', ') +
+              '.');
+    }
+  }
+
+  /// The configuration where variable data is found.
+  final Configuration _configuration;
+
+  Environment(this._configuration);
+
+  /// Looks up the value of the variable with [name].
+  String lookUp(String name) {
+    var variable = _variables[name];
+    if (variable == null) {
+      // This shouldn't happen since we validate variables before evaluating
+      // expressions.
+      throw new ArgumentError('Unknown variable "$variable".');
+    }
+
+    return variable.lookUp(_configuration);
+  }
+}
+
+// TODO(rnystrom): There's some overlap between these and _Option in
+// options.dart. Unify?
+/// Describes a variable name whose value can be tested in a status file.
+///
+/// Each variable is an enumerated string type that only accepts a limited range
+/// of values. Each instance of this class defines one variable, the values it
+/// permits, and the logic needed to look up the variable's value from a
+/// [Configuration]
+class _Variable {
+  final _LookUpFunction _lookUp;
+  final List<String> allowedValues;
+
+  _Variable(this._lookUp, Iterable<String> allowed)
+      : allowedValues = allowed.toList();
+
+  /// Creates a Boolean variable with allowed values "true" and "false".
+  _Variable.bool(_BoolLookUpFunction lookUp)
+      : _lookUp = ((configuration) => lookUp(configuration).toString()),
+        allowedValues = const ["true", "false"];
+
+  String lookUp(Configuration configuration) => _lookUp(configuration);
+}