Add getTarget method to CompilerCommandLine

The method is used to create an instance of a backend target class.
CompilerCommandLine already has the necessary information for this ("target"
name string and "strongMode" flag).  Additionally, a backed target instance is
now not created in fasta.dart/parseScriptInFileSystem, but should be passed at
the call site.

R=ahe@google.com, scheglov@google.com

Review-Url: https://codereview.chromium.org/2932513003 .

pkg/front_end/lib/src/fasta/compile_platform.dart

@@ -24,8 +24,6 @@ import 'ticker.dart' show Ticker;
 
 import 'translate_uri.dart' show TranslateUri;
 
-import 'package:kernel/target/targets.dart' show getTarget, TargetFlags;
-
 const int iterations = const int.fromEnvironment("iterations", defaultValue: 1);
 
 Future mainEntryPoint(List<String> arguments) async {
@@ -73,11 +71,8 @@ Future compilePlatformInternal(CompilerContext c, Ticker ticker, Uri patchedSdk,
       .parse(c.fileSystem, patchedSdk, packages: c.options.packages);
   ticker.logMs("Read packages file");
 
-  DillTarget dillTarget = new DillTarget(
-      ticker,
-      uriTranslator,
-      getTarget(
-          c.options.target, new TargetFlags(strongMode: c.options.strongMode)));
+  DillTarget dillTarget =
+      new DillTarget(ticker, uriTranslator, c.options.target);
   KernelTarget kernelTarget =
       new KernelTarget(c.fileSystem, dillTarget, uriTranslator, c.uriToSource);
 

pkg/front_end/lib/src/fasta/compiler_command_line.dart

@@ -10,6 +10,9 @@ import 'command_line.dart' show CommandLine, argumentError;
 
 import 'compiler_context.dart' show CompilerContext;
 
+import 'package:kernel/target/targets.dart'
+    show Target, getTarget, TargetFlags, targets;
+
 const Map<String, dynamic> optionSpecification = const <String, dynamic>{
   "--compile-sdk": Uri,
   "--fatal": ",",
@@ -60,6 +63,16 @@ class CompilerCommandLine extends CommandLine {
     } else if (arguments.isEmpty) {
       return argumentError(usage, "No Dart file specified.");
     }
+
+    Target target =
+        getTarget(targetName, new TargetFlags(strongMode: strongMode));
+    if (target == null) {
+      return argumentError(
+          usage,
+          "Target '${targetName}' not recognized. "
+          "Valid targets are:\n  ${targets.keys.join("\n  ")}");
+    }
+    options["target"] = target;
   }
 
   Uri get output {
@@ -90,10 +103,12 @@ class CompilerCommandLine extends CommandLine {
 
   bool get strongMode => options.containsKey("--strong-mode");
 
-  String get target {
+  String get targetName {
     return options["-t"] ?? options["--target"] ?? "vm_fasta";
   }
 
+  Target get target => options["target"];
+
   static dynamic withGlobalOptions(String programName, List<String> arguments,
       dynamic f(CompilerContext context)) {
     return CompilerContext.withGlobalOptions(

pkg/front_end/lib/src/fasta/fasta.dart

@@ -18,7 +18,7 @@ import 'package:kernel/binary/ast_to_binary.dart'
 
 import 'package:kernel/kernel.dart' show Library, Program, loadProgramFromBytes;
 
-import 'package:kernel/target/targets.dart' show getTarget, TargetFlags;
+import 'package:kernel/target/targets.dart' show Target;
 
 import 'compiler_command_line.dart' show CompilerCommandLine;
 
@@ -114,11 +114,7 @@ class CompileTask {
   CompileTask(this.c, this.ticker);
 
   DillTarget createDillTarget(TranslateUri uriTranslator) {
-    return new DillTarget(
-        ticker,
-        uriTranslator,
-        getTarget(c.options.target,
-            new TargetFlags(strongMode: c.options.strongMode)));
+    return new DillTarget(ticker, uriTranslator, c.options.target);
   }
 
   KernelTarget createKernelTarget(
@@ -176,17 +172,16 @@ class CompileTask {
 }
 
 Future<CompilationResult> parseScript(
-    Uri fileName, Uri packages, Uri patchedSdk,
-    {bool verbose: false, bool strongMode: false}) async {
-  return parseScriptInFileSystem(
-      fileName, PhysicalFileSystem.instance, packages, patchedSdk,
-      verbose: verbose, strongMode: strongMode);
+    Uri fileName, Uri packages, Uri patchedSdk, Target backendTarget,
+    {bool verbose: false}) async {
+  return parseScriptInFileSystem(fileName, PhysicalFileSystem.instance,
+      packages, patchedSdk, backendTarget,
+      verbose: verbose);
 }
 
-Future<CompilationResult> parseScriptInFileSystem(
-    Uri fileName, FileSystem fileSystem, Uri packages, Uri patchedSdk,
-    {bool verbose: false, bool strongMode: false, String backendTarget}) async {
-  backendTarget ??= "vm_fasta";
+Future<CompilationResult> parseScriptInFileSystem(Uri fileName,
+    FileSystem fileSystem, Uri packages, Uri patchedSdk, Target backendTarget,
+    {bool verbose: false}) async {
   try {
     if (!await fileSystem.entityForUri(fileName).exists()) {
       return new CompilationResult.error(
@@ -202,8 +197,8 @@ Future<CompilationResult> parseScriptInFileSystem(
       TranslateUri uriTranslator =
           await TranslateUri.parse(fileSystem, patchedSdk, packages: packages);
       final Ticker ticker = new Ticker(isVerbose: verbose);
-      final DillTarget dillTarget = new DillTarget(ticker, uriTranslator,
-          getTarget(backendTarget, new TargetFlags(strongMode: strongMode)));
+      final DillTarget dillTarget =
+          new DillTarget(ticker, uriTranslator, backendTarget);
       _appendDillForUri(dillTarget, patchedSdk.resolve('platform.dill'));
       final KernelTarget kernelTarget =
           new KernelTarget(fileSystem, dillTarget, uriTranslator);
@@ -268,6 +263,8 @@ Future writeDepsFile(Uri script, Uri depsFile, Uri output,
   Ticker ticker = new Ticker(isVerbose: verbose);
   await CompilerCommandLine.withGlobalOptions("", [""],
       (CompilerContext c) async {
+    c.options.options["--target"] = backendTarget;
+    c.options.options["--strong-mode"] = false;
     c.options.options["--packages"] = packages;
     if (verbose) {
       c.options.options["--verbose"] = true;
@@ -277,8 +274,8 @@ Future writeDepsFile(Uri script, Uri depsFile, Uri output,
     TranslateUri uriTranslator = await TranslateUri.parse(c.fileSystem, sdk,
         packages: c.options.packages);
     ticker.logMs("Read packages file");
-    DillTarget dillTarget = new DillTarget(ticker, uriTranslator,
-        getTarget(backendTarget, new TargetFlags(strongMode: false)));
+    DillTarget dillTarget =
+        new DillTarget(ticker, uriTranslator, c.options.target);
     _appendDillForUri(dillTarget, platform);
     KernelTarget kernelTarget = new KernelTarget(
         PhysicalFileSystem.instance, dillTarget, uriTranslator, c.uriToSource);

pkg/front_end/lib/src/fasta/vm.dart

@@ -18,6 +18,9 @@ import 'package:front_end/physical_file_system.dart';
 
 import 'fasta.dart' as fasta;
 
+import 'package:kernel/target/targets.dart' show TargetFlags;
+import 'package:kernel/target/vm_fasta.dart' show VmFastaTarget;
+
 /// Compilation status codes.
 ///
 /// Note: The [index] property of these constants must match
@@ -84,9 +87,9 @@ Future<CompilationResult> parseScriptInFileSystem(
   }
 
   try {
-    return await fasta.parseScriptInFileSystem(
-        script, fileSystem, packagesUri, patchedSdk,
-        verbose: verbose, strongMode: strongMode);
+    return await fasta.parseScriptInFileSystem(script, fileSystem, packagesUri,
+        patchedSdk, new VmFastaTarget(new TargetFlags(strongMode: strongMode)),
+        verbose: verbose);
   } catch (err, stack) {
     return new CompilationResult.crash(err, stack);
   }