Move all flags to CompilerOptions (first step to stop passing the compiler to

pkg/compiler/lib/compiler_new.dart

 // Copyright (c) 2015, 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.
 
 /// New Compiler API. This API is under construction, use only internally or
 /// in unittests.
 
 library compiler_new;
 
 import 'dart:async';
 import 'src/apiimpl.dart';
+import 'src/commandline_options.dart';
+import 'src/diagnostics/diagnostic_listener.dart' show DiagnosticOptions;
+
 import 'compiler.dart' show Diagnostic, PackagesDiscoveryProvider;
 export 'compiler.dart' show Diagnostic, PackagesDiscoveryProvider;
 
 // Unless explicitly allowed, passing `null` for any argument to the
 // methods of library will result in an Error being thrown.
 
 /// Interface for providing the compiler with input. That is, Dart source files,
 /// package config files, etc.
 abstract class CompilerInput {
   /// Returns a future that completes to the source corresponding to [uri].
@@ skipping 42 matching lines @@
   /// [begin] and [end]. No other arguments may be `null`. If [uri] is not
   /// `null`, neither are [begin] and [end]. [uri] indicates the compilation
   /// unit from where the diagnostic originates. [begin] and [end] are
   /// zero-based character offsets from the beginning of the compilation unit.
   /// [message] is the diagnostic message, and [kind] indicates indicates what
   /// kind of diagnostic it is.
   ///
   /// Experimental: [code] gives access to an id for the messages. Currently it
   /// is the [Message] used to create the diagnostic, if available, from which
   /// the [MessageKind] is accessible.
-  void report(var code,
-              Uri uri, int begin, int end, String text, Diagnostic kind);
+  void report(
+      var code, Uri uri, int begin, int end, String text, Diagnostic kind);
 }
 
 /// Information resulting from the compilation.
 class CompilationResult {
   /// `true` if the compilation succeeded, that is, compilation didn't fail due
   /// to compile-time errors and/or internal errors.
   final bool isSuccess;
 
   /// The compiler object used for the compilation.
   ///
   /// Note: The type of [compiler] is implementation dependent and may vary.
   /// Use only for debugging and testing.
   final compiler;
 
   CompilationResult(this.compiler, {this.isSuccess: true});
 }
 
 /// Object for passing options to the compiler.
 class CompilerOptions {
+  /// The entry point of the application that is being compiled.
   final Uri entryPoint;
+
+  /// Root location where SDK libraries are found.
   final Uri libraryRoot;
+
+  /// Package root location.
+  ///
+  /// If not null then [packageConfig] should be null.
   final Uri packageRoot;
+
+  /// Location of the package configuration file.
+  ///
+  /// If not null then [packageRoot] should be null.
   final Uri packageConfig;
+
+  // TODO(sigmund): Move out of here, maybe to CompilerInput. Options should not
+  // hold code, just configuration options.
   final PackagesDiscoveryProvider packagesDiscoveryProvider;
-  final List<String> options;
+
+  /// Resolved constant "environment" values passed to the compiler via the `-D`
+  /// flags.
   final Map<String, dynamic> environment;
 
+  /// Whether we allow mocking compilation of libraries such as dart:io and
+  /// dart:html for unit testing purposes.
+  final bool allowMockCompilation;
+
+  /// Whether the native extension syntax is supported by the frontend.
+  final bool allowNativeExtensions;
+
+  /// Whether to resolve all functions in the program, not just those reachable
+  /// from main. This implies [analyzeOnly] is true as well.
+  final bool analyzeAll;
+
+  /// Whether to disable tree-shaking for the main script. This marks all
+  /// functions in the main script as reachable (not just a function named
+  /// `main`).
+  // TODO(sigmund): rename. The current name seems to indicate that only the
+  // main function is retained, which is the opposite of what this does.
+  final bool analyzeMain;
+
+  /// Whether to run the compiler just for the purpose of analysis. That is, to
+  /// run resolution and type-checking alone, but otherwise do not generate any
+  /// code.
+  final bool analyzeOnly;
+
+  /// Whether to skip analysis of method bodies and field initializers. Implies
+  /// [analyzeOnly].
+  final bool analyzeSignaturesOnly;
+
+  /// ID associated with this sdk build.
+  final String buildId;
+
+  /// Whether there is a build-id available so we can use it on error messages
+  /// and in the emitted output of the compiler.
+  bool get hasBuildId => buildId != _UNDETERMINED_BUILD_ID;
+
+  /// Location where to generate a map containing details of how deferred
+  /// libraries are subdivided.
+  final Uri deferredMapUri;
+
+  /// Whether to disable inlining during the backend optimizations.
+  // TODO(sigmund): negate, so all flags are positive
+  final bool disableInlining;
+
+  /// Several options to configure diagnostic messages.
+  // TODO(sigmund): should we simply embed those options here?
+  final DiagnosticOptions diagnosticOptions;
+
+  /// Whether to disable global type inference.
+  final bool disableTypeInference;
+
+  /// Whether to emit a .json file with a summary of the information used by the
+  /// compiler during optimization. This includes resolution details,
+  /// dependencies between elements, results of type inference, and the output
+  /// code for each function.
+  final bool dumpInfo;
+
+  /// Whether we allow passing an extra argument to `assert`, containing a
+  /// reason for why an assertion fails. (experimental)
+  final bool enableAssertMessage;
+
+  /// Whether to enable the experimental conditional directives feature.
+  final bool enableConditionalDirectives;
+
+  /// Whether the user specified a flag to allow the use of dart:mirrors. This
+  /// silences a warning produced by the compiler.
+  final bool enableExperimentalMirrors;
+
+  /// Whether to enable minification
+  // TODO(sigmund): rename to minify
+  final bool enableMinification;
+
+  /// Whether to model which native classes are live based on annotations on the
+  /// core libraries. If false, all native classes will be included by default.
+  final bool enableNativeLiveTypeAnalysis;
+
+  /// Whether to generate code containing checked-mode assignability checks.
+  final bool enableTypeAssertions;
+
+  /// Whether to generate code containing user's `assert` statements.
+  final bool enableUserAssertions;
+
+  /// Whether to generate output even when there are compile-time errors.
+  final bool generateCodeWithCompileTimeErrors;
+
+  /// Whether to generate a source-map file together with the output program.
+  final bool generateSourceMap;
+
+  /// Whether some values are cached for reuse in incremental compilation.
+  /// Incremental compilation allows calling `Compiler.run` more than once
+  /// (experimental).
+  final bool hasIncrementalSupport;
+
+  /// URI of the main output if the compiler is generating source maps.
+  final Uri outputUri;
+
+  /// Location of the platform configuration file.
+  final Uri platformConfigUri;
+
+  /// Whether to emit URIs in the reflection metadata.
+  final bool preserveUris;
+
+  /// URI where the compiler should generate the output source map file.
+  final Uri sourceMapUri;
+
+  /// The compiler is run from the build bot.
+  final bool testMode;
+
+  /// Whether to trust JS-interop annotations. (experimental)
+  final bool trustJSInteropTypeAnnotations;
+
+  /// Whether to trust primitive types during inference and optimizations.
+  final bool trustPrimitives;
+
+  /// Whether to trust type annotations during inference and optimizations.
+  final bool trustTypeAnnotations;
+
+  /// Whether to generate code compliant with content security policy (CSP).
+  final bool useContentSecurityPolicy;
+
+  /// Use the experimental CPS based backend.
+  final bool useCpsIr;
+
+  /// When obfuscating for minification, whether to use the frequency of a name
+  /// as an heuristic to pick shorter names.
+  final bool useFrequencyNamer;
+
+  /// Whether to use the new source-information implementation for source-maps.
+  /// (experimental)
+  final bool useNewSourceInfo;
+
+  /// Whether the user requested to use the fast startup emitter. The full
+  /// emitter might still be used if the program uses dart:mirrors.
+  final bool useStartupEmitter;
+
+  /// Enable verbose printing during compilation. Includes progress messages
+  /// during each phase and a time-breakdown between phases at the end.
+  final bool verbose;
+
+
+  // -------------------------------------------------
+  // Options for deprecated features
+  // -------------------------------------------------
+  // TODO(sigmund): delete these as we delete the underlying features
+
+  /// Whether to preserve comments while scanning (only use for dart:mirrors).
+  final bool preserveComments;
+
+  /// Whether to emit JavaScript (false enables dart2dart).
+  final bool emitJavaScript;
+
+  /// When using dart2dart, whether to use the multi file format.
+  final bool dart2dartMultiFile;
+
+  /// Strip option used by dart2dart.
+  final List<String> strips;
+
+  /// Create an options object by parsing flags from [options].
+  factory CompilerOptions.parse(
+      {Uri entryPoint,
+      Uri libraryRoot,
+      Uri packageRoot,
+      Uri packageConfig,
+      PackagesDiscoveryProvider packagesDiscoveryProvider,
+      Map<String, dynamic> environment: const <String, dynamic>{},
+      List<String> options}) {
+    return new CompilerOptions(
+        entryPoint: entryPoint,
+        libraryRoot: libraryRoot,
+        packageRoot: packageRoot,
+        packageConfig: packageConfig,
+        packagesDiscoveryProvider: packagesDiscoveryProvider,
+        environment: environment,
+        allowMockCompilation: _hasOption(options, Flags.allowMockCompilation),
+        allowNativeExtensions: _hasOption(options, Flags.allowNativeExtensions),
+        analyzeAll: _hasOption(options, Flags.analyzeAll),
+        analyzeMain: _hasOption(options, Flags.analyzeMain),
+        analyzeOnly: _hasOption(options, Flags.analyzeOnly),
+        analyzeSignaturesOnly: _hasOption(options, Flags.analyzeSignaturesOnly),
+        buildId: _extractStringOption(
+            options, '--build-id=', _UNDETERMINED_BUILD_ID),
+        dart2dartMultiFile: _hasOption(options, '--output-type=dart-multi'),
+        deferredMapUri: _extractUriOption(options, '--deferred-map='),
+        diagnosticOptions: new DiagnosticOptions(
+            suppressWarnings: _hasOption(options, Flags.suppressWarnings),
+            fatalWarnings: _hasOption(options, Flags.fatalWarnings),
+            suppressHints: _hasOption(options, Flags.suppressHints),
+            terseDiagnostics: _hasOption(options, Flags.terse),
+            shownPackageWarnings:
+                _extractOptionalCsvOption(options, Flags.showPackageWarnings)),
+        disableInlining: _hasOption(options, Flags.disableInlining),
+        disableTypeInference: _hasOption(options, Flags.disableTypeInference),
+        dumpInfo: _hasOption(options, Flags.dumpInfo),
+        emitJavaScript: !(_hasOption(options, '--output-type=dart') ||
+            _hasOption(options, '--output-type=dart-multi')),
+        enableAssertMessage: _hasOption(options, Flags.enableAssertMessage),
+        enableConditionalDirectives:
+            _hasOption(options, Flags.conditionalDirectives),
+        enableExperimentalMirrors:
+            _hasOption(options, Flags.enableExperimentalMirrors),
+        enableMinification: _hasOption(options, Flags.minify),
+        enableNativeLiveTypeAnalysis:
+            !_hasOption(options, Flags.disableNativeLiveTypeAnalysis),
+        enableTypeAssertions: _hasOption(options, Flags.enableCheckedMode),
+        enableUserAssertions: _hasOption(options, Flags.enableCheckedMode),
+        generateCodeWithCompileTimeErrors:
+            _hasOption(options, Flags.generateCodeWithCompileTimeErrors),
+        generateSourceMap: !_hasOption(options, Flags.noSourceMaps),
+        hasIncrementalSupport: _forceIncrementalSupport ||
+            _hasOption(options, Flags.incrementalSupport),
+        outputUri: _extractUriOption(options, '--out='),
+        platformConfigUri: _resolvePlatformConfigFromOptions(
+            libraryRoot, options),
+        preserveComments: _hasOption(options, Flags.preserveComments),
+        preserveUris: _hasOption(options, Flags.preserveUris),
+        sourceMapUri: _extractUriOption(options, '--source-map='),
+        strips: _extractCsvOption(options, '--force-strip='),
+        testMode: _hasOption(options, Flags.testMode),
+        trustJSInteropTypeAnnotations:
+            _hasOption(options, Flags.trustJSInteropTypeAnnotations),
+        trustPrimitives: _hasOption(options, Flags.trustPrimitives),
+        trustTypeAnnotations: _hasOption(options, Flags.trustTypeAnnotations),
+        useContentSecurityPolicy:
+            _hasOption(options, Flags.useContentSecurityPolicy),
+        useCpsIr: _hasOption(options, Flags.useCpsIr),
+        useFrequencyNamer:
+            !_hasOption(options, Flags.noFrequencyBasedMinification),
+        useNewSourceInfo: _hasOption(options, Flags.useNewSourceInfo),
+        useStartupEmitter: _hasOption(options, Flags.fastStartup),
+        verbose: _hasOption(options, Flags.verbose));
+  }
+
   /// Creates an option object for the compiler.
-  // TODO(johnniwinther): Expand comment when [options] are explicit as named
-  // arguments.
+  ///
+  /// This validates and normalizes dependent options to be consistent. For
+  /// example, if [analyzeAll] is true, the resulting options object will also
+  /// have [analyzeOnly] as true.
   factory CompilerOptions(
       {Uri entryPoint,
-       Uri libraryRoot,
-       Uri packageRoot,
-       Uri packageConfig,
-       PackagesDiscoveryProvider packagesDiscoveryProvider,
-       List<String> options: const <String>[],
-       Map<String, dynamic> environment: const <String, dynamic>{}}) {
-    if (entryPoint == null) {
-      throw new ArgumentError("entryPoint must be non-null");
+      Uri libraryRoot,
+      Uri packageRoot,
+      Uri packageConfig,
+      PackagesDiscoveryProvider packagesDiscoveryProvider,
+      Map<String, dynamic> environment: const <String, dynamic>{},
+      bool allowMockCompilation: false,
+      bool allowNativeExtensions: false,
+      bool analyzeAll: false,
+      bool analyzeMain: false,
+      bool analyzeOnly: false,
+      bool analyzeSignaturesOnly: false,
+      String buildId: _UNDETERMINED_BUILD_ID,
+      bool dart2dartMultiFile: false,
+      Uri deferredMapUri: null,
+      DiagnosticOptions diagnosticOptions: const DiagnosticOptions(),
+      bool disableInlining: false,
+      bool disableTypeInference: false,
+      bool dumpInfo: false,
+      bool emitJavaScript: true,
+      bool enableAssertMessage: false,
+      bool enableConditionalDirectives: false,
+      bool enableExperimentalMirrors: false,
+      bool enableMinification: false,
+      bool enableNativeLiveTypeAnalysis: true,
+      bool enableTypeAssertions: false,
+      bool enableUserAssertions: false,
+      bool generateCodeWithCompileTimeErrors: false,
+      bool generateSourceMap: true,
+      bool hasIncrementalSupport: false,
+      Uri outputUri: null,
+      Uri platformConfigUri: null,
+      bool preserveComments: false,
+      bool preserveUris: false,
+      Uri sourceMapUri: null,
+      List<String> strips: const [],
+      bool testMode: false,
+      bool trustJSInteropTypeAnnotations: false,
+      bool trustPrimitives: false,
+      bool trustTypeAnnotations: false,
+      bool useContentSecurityPolicy: false,
+      bool useCpsIr: false,
+      bool useFrequencyNamer: true,
+      bool useNewSourceInfo: false,
+      bool useStartupEmitter: false,
+      bool verbose: false}) {
+    // TODO(sigmund): should entrypoint be here? should we validate it is not
+    // null? In unittests we use the same compiler to analyze or build multiple
+    // entrypoints.
+    if (libraryRoot == null) {
+      throw new ArgumentError("[libraryRoot] is null.");
     }
     if (!libraryRoot.path.endsWith("/")) {
-      throw new ArgumentError("libraryRoot must end with a /");
+      throw new ArgumentError("[libraryRoot] must end with a /");
+    }
+    if (packageRoot != null && packageConfig != null) {
+      throw new ArgumentError("Only one of [packageRoot] or [packageConfig] "
+          "may be given.");
     }
     if (packageRoot != null && !packageRoot.path.endsWith("/")) {
-      throw new ArgumentError("packageRoot must end with a /");
+      throw new ArgumentError("[packageRoot] must end with a /");
     }
-    return new CompilerOptions._(
-        entryPoint,
-        libraryRoot,
-        packageRoot,
-        packageConfig,
-        packagesDiscoveryProvider,
-        options,
-        environment);
+    if (!analyzeOnly) {
+      if (allowNativeExtensions) {
+        throw new ArgumentError(
+            "${Flags.allowNativeExtensions} is only supported in combination "
+            "with ${Flags.analyzeOnly}");
+      }
+    }
+    return new CompilerOptions._(entryPoint, libraryRoot, packageRoot,
+        packageConfig, packagesDiscoveryProvider, environment,
+        allowMockCompilation: allowMockCompilation,
+        allowNativeExtensions: allowNativeExtensions,
+        analyzeAll: analyzeAll,
+        analyzeMain: analyzeMain,
+        analyzeOnly: analyzeOnly || analyzeSignaturesOnly || analyzeAll,
+        analyzeSignaturesOnly: analyzeSignaturesOnly,
+        buildId: buildId,
+        dart2dartMultiFile: dart2dartMultiFile,
+        deferredMapUri: deferredMapUri,
+        diagnosticOptions: diagnosticOptions,
+        disableInlining: disableInlining || hasIncrementalSupport,
+        disableTypeInference: disableTypeInference || !emitJavaScript,
+        dumpInfo: dumpInfo,
+        emitJavaScript: emitJavaScript,
+        enableAssertMessage: enableAssertMessage,
+        enableConditionalDirectives: enableConditionalDirectives,
+        enableExperimentalMirrors: enableExperimentalMirrors,
+        enableMinification: enableMinification,
+        enableNativeLiveTypeAnalysis: enableNativeLiveTypeAnalysis,
+        enableTypeAssertions: enableTypeAssertions,
+        enableUserAssertions: enableUserAssertions,
+        generateCodeWithCompileTimeErrors: generateCodeWithCompileTimeErrors,
+        generateSourceMap: generateSourceMap,
+        hasIncrementalSupport: hasIncrementalSupport,
+        outputUri: outputUri,
+        platformConfigUri: platformConfigUri ?? _resolvePlatformConfig(
+           libraryRoot, null, !emitJavaScript, const []),
+        preserveComments: preserveComments,
+        preserveUris: preserveUris,
+        sourceMapUri: sourceMapUri,
+        strips: strips,
+        testMode: testMode,
+        trustJSInteropTypeAnnotations: trustJSInteropTypeAnnotations,
+        trustPrimitives: trustPrimitives,
+        trustTypeAnnotations: trustTypeAnnotations,
+        useContentSecurityPolicy: useContentSecurityPolicy,
+        useCpsIr: useCpsIr,
+        useFrequencyNamer: useFrequencyNamer,
+        useNewSourceInfo: useNewSourceInfo,
+        useStartupEmitter: useStartupEmitter,
+        verbose: verbose);
   }
 
-  CompilerOptions._(
-      this.entryPoint,
-      this.libraryRoot,
-      this.packageRoot,
-      this.packageConfig,
-      this.packagesDiscoveryProvider,
-      this.options,
-      this.environment);
+  CompilerOptions._(this.entryPoint, this.libraryRoot, this.packageRoot,
+      this.packageConfig, this.packagesDiscoveryProvider, this.environment,
+      {this.allowMockCompilation: false,
+      this.allowNativeExtensions: false,
+      this.analyzeAll: false,
+      this.analyzeMain: false,
+      this.analyzeOnly: false,
+      this.analyzeSignaturesOnly: false,
+      this.buildId: _UNDETERMINED_BUILD_ID,
+      this.dart2dartMultiFile: false,
+      this.deferredMapUri: null,
+      this.diagnosticOptions: null,
+      this.disableInlining: false,
+      this.disableTypeInference: false,
+      this.dumpInfo: false,
+      this.emitJavaScript: true,
+      this.enableAssertMessage: false,
+      this.enableConditionalDirectives: false,
+      this.enableExperimentalMirrors: false,
+      this.enableMinification: false,
+      this.enableNativeLiveTypeAnalysis: false,
+      this.enableTypeAssertions: false,
+      this.enableUserAssertions: false,
+      this.generateCodeWithCompileTimeErrors: false,
+      this.generateSourceMap: true,
+      this.hasIncrementalSupport: false,
+      this.outputUri: null,
+      this.platformConfigUri: null,
+      this.preserveComments: false,
+      this.preserveUris: false,
+      this.sourceMapUri: null,
+      this.strips: const [],
+      this.testMode: false,
+      this.trustJSInteropTypeAnnotations: false,
+      this.trustPrimitives: false,
+      this.trustTypeAnnotations: false,
+      this.useContentSecurityPolicy: false,
+      this.useCpsIr: false,
+      this.useFrequencyNamer: false,
+      this.useNewSourceInfo: false,
+      this.useStartupEmitter: false,
+      this.verbose: false});
 }
 
 /// Returns a future that completes to a [CompilationResult] when the Dart
 /// sources in [options] have been compiled.
 ///
 /// The generated compiler output is obtained by providing a [compilerOutput].
 ///
 /// If the compilation fails, the future's `CompilationResult.isSuccess` is
 /// `false` and [CompilerDiagnostics.report] on [compilerDiagnostics]
 /// is invoked at least once with `kind == Diagnostic.ERROR` or
 /// `kind == Diagnostic.CRASH`.
 Future<CompilationResult> compile(
     CompilerOptions compilerOptions,
     CompilerInput compilerInput,
     CompilerDiagnostics compilerDiagnostics,
     CompilerOutput compilerOutput) {
-
   if (compilerOptions == null) {
     throw new ArgumentError("compilerOptions must be non-null");
   }
   if (compilerInput == null) {
     throw new ArgumentError("compilerInput must be non-null");
   }
   if (compilerDiagnostics == null) {
     throw new ArgumentError("compilerDiagnostics must be non-null");
   }
   if (compilerOutput == null) {
     throw new ArgumentError("compilerOutput must be non-null");
   }
 
   CompilerImpl compiler = new CompilerImpl(
-      compilerInput,
-      compilerOutput,
-      compilerDiagnostics,
-      compilerOptions.libraryRoot,
-      compilerOptions.packageRoot,
-      compilerOptions.options,
-      compilerOptions.environment,
-      compilerOptions.packageConfig,
-      compilerOptions.packagesDiscoveryProvider);
+      compilerInput, compilerOutput, compilerDiagnostics, compilerOptions);
   return compiler.run(compilerOptions.entryPoint).then((bool success) {
     return new CompilationResult(compiler, isSuccess: success);
   });
 }
+
+String _extractStringOption(
+    List<String> options, String prefix, String defaultValue) {
+  for (String option in options) {
+    if (option.startsWith(prefix)) {
+      return option.substring(prefix.length);
+    }
+  }
+  return defaultValue;
+}
+
+Uri _extractUriOption(List<String> options, String prefix) {
+  var option = _extractStringOption(options, prefix, null);
+  return (option == null) ? null : Uri.parse(option);
+}
+
+// CSV: Comma separated values.
+List<String> _extractCsvOption(List<String> options, String prefix) {
+  for (String option in options) {
+    if (option.startsWith(prefix)) {
+      return option.substring(prefix.length).split(',');
+    }
+  }
+  return const <String>[];
+}
+
+/// Extract list of comma separated values provided for [flag]. Returns an
+/// empty list if [option] contain [flag] without arguments. Returns `null` if
+/// [option] doesn't contain [flag] with or without arguments.
+List<String> _extractOptionalCsvOption(List<String> options, String flag) {
+  String prefix = '$flag=';
+  for (String option in options) {
+    if (option == flag) {
+      return const <String>[];
+    }
+    if (option.startsWith(flag)) {
+      return option.substring(prefix.length).split(',');
+    }
+  }
+  return null;
+}
+
+Uri _resolvePlatformConfigFromOptions(Uri libraryRoot, List<String> options) {
+  return _resolvePlatformConfig(libraryRoot,
+      _extractStringOption(options, "--platform-config=", null),
+      _hasOption(options, '--output-type=dart'),
+      _extractCsvOption(options, '--categories='));
+}
+
+Uri _resolvePlatformConfig(Uri libraryRoot,
+    String platformConfigPath, bool isDart2Dart, Iterable<String> categories) {
+  if (platformConfigPath != null) {
+    return libraryRoot.resolve(platformConfigPath);
+  } else if (isDart2Dart) {
+    return libraryRoot.resolve(_dart2dartPlatform);
+  } else {
+    if (categories.length == 0) {
+      return libraryRoot.resolve(_clientPlatform);
+    }
+    assert(categories.length <= 2);
+    if (categories.contains("Client")) {
+      if (categories.contains("Server")) {
+        return libraryRoot.resolve(_sharedPlatform);
+      }
+      return libraryRoot.resolve(_clientPlatform);
+    }
+    assert(categories.contains("Server"));
+    return libraryRoot.resolve(_serverPlatform);
+  }
+}
+
+bool _hasOption(List<String> options, String option) {
+  return options.indexOf(option) >= 0;
+}
+
+/// Locations of the platform descriptor files relative to the library root.
+const String _clientPlatform = "lib/dart_client.platform";
+const String _serverPlatform = "lib/dart_server.platform";
+const String _sharedPlatform = "lib/dart_shared.platform";
+const String _dart2dartPlatform = "lib/dart2dart.platform";
+
+const String _UNDETERMINED_BUILD_ID = "build number could not be determined";
+const bool _forceIncrementalSupport =
+    const bool.fromEnvironment('DART2JS_EXPERIMENTAL_INCREMENTAL_SUPPORT');