Support steps that only run on the main module

I'll work on a follow up CL to add unit tests for it.

Change-Id: Ifa142731eb60ba14fb3187b5f3e9333cef12f751
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/102124
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Sigmund Cherem <sigmund@google.com>

pkg/modular_test/lib/src/loader.dart

@@ -60,7 +60,7 @@ Future<ModularTest> loadTest(Uri uri) async {
         var relativeUri = Uri.parse(fileName);
         var isMain = moduleName == 'main';
         var module = Module(moduleName, [], testUri, [relativeUri],
-            mainSource: isMain ? relativeUri : null);
+            mainSource: isMain ? relativeUri : null, isMain: isMain);
         if (isMain) mainModule = module;
         modules[moduleName] = module;
       } else if (fileName == '.packages') {

pkg/modular_test/lib/src/pipeline.dart

@@ -39,11 +39,15 @@ class ModularStep {
   /// Data that this step produces.
   final DataId resultId;
 
+  /// Whether this step is only executed on the main module.
+  final bool onlyOnMain;
+
   ModularStep(
       {this.needsSources: true,
       this.dependencyDataNeeded: const [],
       this.moduleDataNeeded: const [],
-      this.resultId});
+      this.resultId,
+      this.onlyOnMain: false});
 }
 
 /// An object to uniquely identify modular data produced by a modular step.
@@ -124,6 +128,7 @@ abstract class Pipeline<S extends ModularStep> {
     }
     parentDependencies.addAll(transitiveDependencies);
 
+    if (step.onlyOnMain && !module.isMain) return;
     // Include only requested data from transitive dependencies.
     Map<Module, Set<DataId>> visibleData = {};
 

pkg/modular_test/lib/src/suite.dart

@@ -41,8 +41,11 @@ class Module {
   /// package name matches the module name.
   bool isPackage;
 
+  /// Whether this is the main entry module of a test.
+  bool isMain;
+
   Module(this.name, this.dependencies, this.rootUri, this.sources,
-      {this.mainSource, this.isPackage: false}) {
+      {this.mainSource, this.isPackage: false, this.isMain: false}) {
     if (!_validModuleName.hasMatch(name)) {
       throw ArgumentError("invalid module name: $name");
     }

pkg/modular_test/test/io_pipeline_test.dart

@@ -86,6 +86,7 @@ class SourceOnlyStep implements IOModularStep {
   final bool needsSources;
   List<DataId> get dependencyDataNeeded => const [];
   List<DataId> get moduleDataNeeded => const [];
+  bool get onlyOnMain => false;
 
   SourceOnlyStep(this.action, this.resultId, this.needsSources);
 
@@ -111,6 +112,7 @@ class ModuleDataStep implements IOModularStep {
   final List<DataId> moduleDataNeeded;
   final DataId resultId;
   final DataId inputId;
+  bool get onlyOnMain => false;
 
   ModuleDataStep(this.action, this.inputId, this.resultId, bool requestInput)
       : moduleDataNeeded = requestInput ? [inputId] : [];
@@ -134,6 +136,7 @@ class LinkStep implements IOModularStep {
   final DataId inputId;
   final DataId depId;
   final DataId resultId;
+  bool get onlyOnMain => false;
 
   LinkStep(this.action, this.inputId, this.depId, this.resultId,
       bool requestDependencies)

pkg/modular_test/test/loader/loader_test.dart

@@ -75,7 +75,8 @@ String _dumpAsText(ModularTest test) {
       buffer.write('\n');
     }
     buffer.write(module.name);
-    if (test.mainModule == module) {
+    if (module.isMain) {
+      Expect.equals(test.mainModule, module);
       buffer.write('\n  **main module**');
     }
     buffer.write('\n  is package? ${module.isPackage ? 'yes' : 'no'}');

pkg/modular_test/test/memory_pipeline_test.dart

@@ -64,6 +64,7 @@ class SourceOnlyStep implements MemoryModularStep {
   final bool needsSources;
   List<DataId> get dependencyDataNeeded => const [];
   List<DataId> get moduleDataNeeded => const [];
+  bool get onlyOnMain => false;
 
   SourceOnlyStep(this.action, this.resultId, this.needsSources);
 
@@ -84,6 +85,7 @@ class ModuleDataStep implements MemoryModularStep {
   final List<DataId> moduleDataNeeded;
   final DataId resultId;
   final DataId inputId;
+  bool get onlyOnMain => false;
 
   ModuleDataStep(this.action, this.inputId, this.resultId, bool requestInput)
       : moduleDataNeeded = requestInput ? [inputId] : [];
@@ -104,6 +106,7 @@ class LinkStep implements MemoryModularStep {
   final DataId inputId;
   final DataId depId;
   final DataId resultId;
+  bool get onlyOnMain => false;
 
   LinkStep(this.action, this.inputId, this.depId, this.resultId,
       bool requestDependencies)