Reapply "Tweak public APIs and use them in patch_sdk, dart2js, and kernel-service.""

pkg/front_end/lib/kernel_generator.dart

Index: pkg/front_end/lib/kernel_generator.dart
diff --git a/pkg/front_end/lib/kernel_generator.dart b/pkg/front_end/lib/kernel_generator.dart
index e0ba4c782e326b5dcb2b06f745b1e2e2acdbd823..d6a40a542de351697f51fc9a63b4edce6856b97c 100644
--- a/pkg/front_end/lib/kernel_generator.dart
+++ b/pkg/front_end/lib/kernel_generator.dart
@@ -5,19 +5,14 @@
 /// Defines the front-end API for converting source code to Dart Kernel objects.
 library front_end.kernel_generator;
 
-import 'compiler_options.dart';
 import 'dart:async' show Future;
 import 'dart:async';
-import 'package:front_end/src/base/processed_options.dart';
-import 'src/fasta/dill/dill_target.dart' show DillTarget;
-import 'src/fasta/errors.dart' show InputError;
-import 'src/fasta/kernel/kernel_target.dart' show KernelTarget;
+
 import 'package:kernel/kernel.dart' show Program;
-import 'package:kernel/target/targets.dart' show TargetFlags;
-import 'package:kernel/target/vm_fasta.dart' show VmFastaTarget;
-import 'src/fasta/ticker.dart' show Ticker;
-import 'src/fasta/translate_uri.dart' show TranslateUri;
-import 'src/simple_error.dart';
+
+import 'compiler_options.dart';
+import 'src/base/processed_options.dart';
+import 'src/kernel_generator_impl.dart';
 
 /// Generates a kernel representation of the program whose main library is in
 /// the given [source].
@@ -31,73 +26,36 @@ import 'src/simple_error.dart';
 /// If `compileSdk` in [options] is true, the generated program will include
 /// code for the SDK.
 ///
-/// If summaries are provided in [options], they will be used to speed up
-/// the process. If in addition `compileSdk` is false, then the resulting
-/// program will not contain the sdk contents. This is useful when building apps
-/// for platforms that already embed the sdk (e.g. the VM), so there is no need
-/// to spend time and space rebuilding it.
+/// If summaries are provided in [options], the compiler will use them instead
+/// of compiling the libraries contained in those summaries. This is useful, for
+/// example, when compiling for platforms that already embed those sources (like
+/// the sdk in the standalone VM).
+///
+/// The input [source] is expected to be a script with a main method, otherwise
+/// an error is reported.
+// TODO(sigmund): rename to kernelForScript?
 Future<Program> kernelForProgram(Uri source, CompilerOptions options) async {
-  var fs = options.fileSystem;
-  report(String msg) {
-    options.onError(new SimpleError(msg));
-    return null;
-  }
-
-  if (!await fs.entityForUri(source).exists()) {
-    return report("Entry-point file not found: $source");
-  }
-
-  var pOptions = new ProcessedOptions(options);
+  var pOptions = new ProcessedOptions(options, false, [source]);
+  var program = (await generateKernel(pOptions))?.program;
+  if (program == null) return null;
 
-  if (!await pOptions.validateOptions()) return null;
-
-  try {
-    TranslateUri uriTranslator = await pOptions.getUriTranslator();
-
-    var dillTarget = new DillTarget(new Ticker(isVerbose: false), uriTranslator,
-        new VmFastaTarget(new TargetFlags(strongMode: options.strongMode)));
-    var summary = await pOptions.sdkSummaryProgram;
-    if (summary != null) {
-      dillTarget.loader.appendLibraries(summary);
-    }
-
-    var kernelTarget =
-        new KernelTarget(options.fileSystem, dillTarget, uriTranslator);
-    kernelTarget.read(source);
-
-    await dillTarget.buildOutlines();
-    await kernelTarget.buildOutlines();
-    Program program = await kernelTarget.buildProgram(trimDependencies: true);
-
-    if (kernelTarget.errors.isNotEmpty) {
-      kernelTarget.errors.forEach(report);
-      return null;
-    }
-
-    if (program.mainMethod == null) {
-      return report("No 'main' method found.");
-    }
-
-    if (!options.compileSdk) {
-      // TODO(sigmund): ensure that the result is not including
-      // sources for the sdk, only external references.
-    }
-    return program;
-  } on InputError catch (e) {
-    options.onError(new SimpleError(e.format()));
+  if (program.mainMethod == null) {
+    pOptions.reportError("No 'main' method found.");
     return null;
   }
+
+  return program;
 }
 
-/// Generates a kernel representation for a build unit.
+/// Generates a kernel representation for a build unit containing [sources].
 ///
-/// Intended for modular compilation.
+/// A build unit is a collection of libraries that are compiled together.
+/// Libraries in the build unit may depend on each other and may have
+/// dependencies to libraries in other build units. Unlinke library
+/// dependencies, build unit dependencies must be acyclic.
 ///
-/// The build unit by default contains only the source files in [sources]
-/// (including library and part files), but if
-/// [CompilerOptions.chaseDependencies] is true, it may include some additional
-/// source files.  All of the library files are transformed into Dart Kernel
-/// Library objects.
+/// This API is intended for modular compilation. Dependencies to other build
+/// units are specified using [CompilerOptions.inputSummaries].
 ///
 /// By default, the compilation process is hermetic, meaning that the only files
 /// which will be read are those listed in [sources],
@@ -115,72 +73,11 @@ Future<Program> kernelForProgram(Uri source, CompilerOptions options) async {
 /// are also listed in the build unit sources, otherwise an error results.  (It
 /// is not permitted to refer to a part file declared in another build unit).
 ///
-/// The return value is a [Program] object with no main method set.
-/// TODO(paulberry): would it be better to define a data type in kernel to
-/// represent a bundle of all the libraries in a given build unit?
-///
-/// TODO(paulberry): does additional information need to be output to allow the
-/// caller to match up referenced elements to the summary files they were
-/// obtained from?
+/// The return value is a [Program] object with no main method set. The
+/// [Program] includes external libraries for those libraries loaded through
+/// summaries.
 Future<Program> kernelForBuildUnit(
     List<Uri> sources, CompilerOptions options) async {
-  var fs = options.fileSystem;
-  report(String msg) {
-    options.onError(new SimpleError(msg));
-    return null;
-  }
-
-  if (!options.chaseDependencies) {
-    // TODO(sigmund): add support, most likely we can do so by adding a wrapper
-    // on top of filesystem that restricts reads to a set of known files.
-    report("hermetic mode (chaseDependencies = false) is not implemented");
-    return null;
-  }
-
-  for (var source in sources) {
-    if (!await fs.entityForUri(source).exists()) {
-      return report("Entry-point file not found: $source");
-    }
-  }
-
-  var pOptions = new ProcessedOptions(options);
-
-  if (!await pOptions.validateOptions()) return null;
-
-  try {
-    TranslateUri uriTranslator = await pOptions.getUriTranslator();
-
-    var dillTarget = new DillTarget(new Ticker(isVerbose: false), uriTranslator,
-        new VmFastaTarget(new TargetFlags(strongMode: options.strongMode)));
-    var summary = await pOptions.sdkSummaryProgram;
-    if (summary != null) {
-      dillTarget.loader.appendLibraries(summary);
-    }
-
-    // TODO(sigmund): this is likely not going to work if done naively: if
-    // summaries contain external references we need to ensure they are loaded
-    // in a specific order.
-    for (var inputSummary in await pOptions.inputSummariesPrograms) {
-      dillTarget.loader.appendLibraries(inputSummary);
-    }
-
-    await dillTarget.buildOutlines();
-
-    var kernelTarget =
-        new KernelTarget(options.fileSystem, dillTarget, uriTranslator);
-    sources.forEach(kernelTarget.read);
-    await kernelTarget.buildOutlines();
-
-    Program program = await kernelTarget.buildProgram(trimDependencies: true);
-
-    if (kernelTarget.errors.isNotEmpty) {
-      kernelTarget.errors.forEach(report);
-      return null;
-    }
-
-    return program;
-  } on InputError catch (e) {
-    options.onError(new SimpleError(e.format()));
-    return null;
-  }
+  return (await generateKernel(new ProcessedOptions(options, true, sources)))
+      ?.program;
 }