[cfe] Add --no-deps option to compile_platform script

This allows for disabling the generation of .d deps file when compiling
the platform dill files.

Change-Id: I37774f0dbdae7863fc1cf53b1c5e0d29c6bbdf2c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153765
Reviewed-by: David Morgan <davidmorgan@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

Author: johnniwinther

pkg/front_end/lib/src/api_prototype/compiler_options.dart

@@ -236,6 +236,10 @@ class CompilerOptions {
       "."
       "${kernel.defaultLanguageVersion.minor}";
 
+  /// If `true`, a '.d' file with input dependencies is generated when
+  /// compiling the platform dill.
+  bool emitDeps = true;
+
   bool equivalent(CompilerOptions other,
       {bool ignoreOnDiagnostic: true,
       bool ignoreVerbose: true,
@@ -290,6 +294,7 @@ class CompilerOptions {
     if (writeFileOnCrashReport != other.writeFileOnCrashReport) return false;
     if (nnbdMode != other.nnbdMode) return false;
     if (currentSdkVersion != other.currentSdkVersion) return false;
+    if (emitDeps != other.emitDeps) return false;
 
     return true;
   }

pkg/front_end/lib/src/base/command_line_options.dart

@@ -27,6 +27,7 @@ class Flags {
   static const String help = "--help";
   static const String librariesJson = "--libraries-json";
   static const String noDefines = "--no-defines";
+  static const String noDeps = "--no-deps";
   static const String output = "--output";
   static const String packages = "--packages";
   static const String platform = "--platform";

pkg/front_end/lib/src/base/processed_options.dart

@@ -170,6 +170,8 @@ class ProcessedOptions {
 
   bool get throwOnWarningsForDebugging => _raw.throwOnWarningsForDebugging;
 
+  bool get emitDeps => _raw.emitDeps;
+
   NnbdMode get nnbdMode => _raw.nnbdMode;
 
   /// The entry-points provided to the compiler.

pkg/front_end/tool/_fasta/command_line.dart

@@ -197,6 +197,7 @@ const Map<String, ValueSpecification> optionSpecification =
   Flags.verbose: const BoolValue(false),
   Flags.verify: const BoolValue(false),
   Flags.linkDependencies: const UriListValue(),
+  Flags.noDeps: const BoolValue(false),
   "-D": const DefineValue(),
   "-h": const AliasValue(Flags.help),
   "--out": const AliasValue(Flags.output),
@@ -256,6 +257,8 @@ ProcessedOptions analyzeCommandLine(String programName,
 
   final bool noDefines = options[Flags.noDefines];
 
+  final bool noDeps = options[Flags.noDeps];
+
   final bool verify = options[Flags.verify];
 
   final bool dumpIr = options[Flags.dumpIr];
@@ -341,7 +344,8 @@ ProcessedOptions analyzeCommandLine(String programName,
     ..experimentalFlags = experimentalFlags
     ..environmentDefines = noDefines ? null : parsedArguments.defines
     ..nnbdMode = nnbdMode
-    ..additionalDills = linkDependencies;
+    ..additionalDills = linkDependencies
+    ..emitDeps = !noDeps;
 
   if (programName == "compile_platform") {
     if (arguments.length != 5) {

pkg/front_end/tool/_fasta/entry_points.dart

@@ -434,17 +434,19 @@ Future<void> compilePlatformInternal(CompilerContext c, Uri fullOutput,
 
   c.options.ticker.logMs("Wrote component to ${fullOutput.toFilePath()}");
 
-  List<Uri> deps = result.deps.toList();
-  for (Uri dependency in await computeHostDependencies(hostPlatform)) {
-    // Add the dependencies of the compiler's own sources.
-    if (dependency != outlineOutput) {
-      // We're computing the dependencies for [outlineOutput], so we shouldn't
-      // include it in the deps file.
-      deps.add(dependency);
+  if (c.options.emitDeps) {
+    List<Uri> deps = result.deps.toList();
+    for (Uri dependency in await computeHostDependencies(hostPlatform)) {
+      // Add the dependencies of the compiler's own sources.
+      if (dependency != outlineOutput) {
+        // We're computing the dependencies for [outlineOutput], so we shouldn't
+        // include it in the deps file.
+        deps.add(dependency);
+      }
     }
+    await writeDepsFile(fullOutput,
+        new File(new File.fromUri(fullOutput).path + ".d").uri, deps);
   }
-  await writeDepsFile(
-      fullOutput, new File(new File.fromUri(fullOutput).path + ".d").uri, deps);
 }
 
 Future<List<Uri>> computeHostDependencies(Uri hostPlatform) async {