Started loading the plugin registrant specified by the framework instead of looking for it.

Author: gaaclarke

runtime/BUILD.gn

@@ -187,6 +187,7 @@ if (enable_unittests) {
     public_deps = [
       ":plugin_registrant",
       "//flutter/fml",
+      "//flutter/runtime:dart_plugin_registrant",
       "//flutter/testing",
       "//flutter/testing:fixture_test",
     ]

runtime/dart_isolate.cc

@@ -707,6 +707,9 @@ bool DartIsolate::RunFromLibrary(std::optional<std::string> library_name,
                                : tonic::ToDart("main");
 
   if (!FindAndInvokeDartPluginRegistrant()) {
+    // TODO(gaaclarke): Remove once the framework PR lands that uses `--source`
+    // to compile the Dart Plugin Registrant
+    // (https://github.com/flutter/flutter/pull/100572).
     InvokeDartPluginRegistrantIfAvailable(library_handle);
   }
 

runtime/dart_plugin_registrant.cc

@@ -6,40 +6,14 @@
 
 #include <string>
 
+#include "flutter/fml/logging.h"
 #include "flutter/fml/trace_event.h"
 #include "third_party/tonic/converter/dart_converter.h"
 #include "third_party/tonic/logging/dart_invoke.h"
 
 namespace flutter {
 
-namespace {
-bool EndsWith(const std::string& str, const std::string& ending) {
-  if (str.size() >= ending.size()) {
-    return (0 ==
-            str.compare(str.size() - ending.size(), ending.size(), ending));
-  } else {
-    return false;
-  }
-}
-
-Dart_Handle FindDartPluginRegistrantLibrary() {
-  // TODO(99308): Instead of finding this, it could be passed down from the
-  // tool.
-  Dart_Handle libraries = Dart_GetLoadedLibraries();
-  intptr_t length = 0;
-  Dart_ListLength(libraries, &length);
-  for (intptr_t i = 0; i < length; ++i) {
-    Dart_Handle library = Dart_ListGetAt(libraries, i);
-    std::string library_name =
-        tonic::DartConverter<std::string>::FromDart(Dart_ToString(library));
-    if (EndsWith(library_name,
-                 "dart_tool/flutter_build/dart_plugin_registrant.dart'")) {
-      return library;
-    }
-  }
-  return Dart_Null();
-}
-}  // namespace
+const char* dart_plugin_registrant_library_override = nullptr;
 
 bool InvokeDartPluginRegistrantIfAvailable(Dart_Handle library_handle) {
   TRACE_EVENT0("flutter", "InvokeDartPluginRegistrantIfAvailable");
@@ -65,12 +39,30 @@ bool InvokeDartPluginRegistrantIfAvailable(Dart_Handle library_handle) {
 }
 
 bool FindAndInvokeDartPluginRegistrant() {
-  auto dart_plugin_registrant_library = FindDartPluginRegistrantLibrary();
-  if (!Dart_IsNull(dart_plugin_registrant_library)) {
-    return InvokeDartPluginRegistrantIfAvailable(
-        dart_plugin_registrant_library);
-  } else {
+  std::string library_name =
+      dart_plugin_registrant_library_override == nullptr
+          ? "package:flutter/src/dart_plugin_registrant.dart"
+          : dart_plugin_registrant_library_override;
+  Dart_Handle library = Dart_LookupLibrary(tonic::ToDart(library_name));
+  if (Dart_IsError(library)) {
     return false;
   }
+  Dart_Handle registrant_file_uri =
+      Dart_GetField(library, tonic::ToDart("dartPluginRegistrantLibrary"));
+  if (Dart_IsError(registrant_file_uri)) {
+    // TODO(gaaclarke): Find a way to remove this branch so the field is
+    // required. I couldn't get it working with unit tests.
+    return InvokeDartPluginRegistrantIfAvailable(library);
+  } else {
+    std::string registrant_file_uri_string =
+        tonic::DartConverter<std::string>::FromDart(registrant_file_uri);
+    if (registrant_file_uri_string.empty()) {
+      FML_LOG(ERROR) << "Unexpected empty dartPluginRegistrantLibrary.";
+      return false;
+    } else {
+      Dart_Handle registrant_library = Dart_LookupLibrary(registrant_file_uri);
+      return InvokeDartPluginRegistrantIfAvailable(registrant_library);
+    }
+  }
 }
 }  // namespace flutter

runtime/dart_plugin_registrant.h

@@ -9,6 +9,10 @@
 
 namespace flutter {
 
+/// The name of the library where the Dart Plugin Registrant will be looked for.
+/// This is available for testing.
+extern const char* dart_plugin_registrant_library_override;
+
 /// Looks for the Dart Plugin Registrant in `library_handle` and invokes it if
 /// it is found.
 /// @return `true` when the registrant has been invoked.

runtime/dart_plugin_registrant_unittests.cc

@@ -4,7 +4,9 @@
 
 #include "flutter/runtime/dart_isolate.h"
 
+#include <cstdlib>
 #include "flutter/fml/paths.h"
+#include "flutter/runtime/dart_plugin_registrant.h"
 #include "flutter/runtime/dart_vm.h"
 #include "flutter/runtime/dart_vm_lifecycle.h"
 #include "flutter/testing/dart_isolate_runner.h"
@@ -23,6 +25,30 @@ const std::string elf_file_name = "plugin_registrant_app_elf_snapshot.so";
 class DartIsolateTest : public FixtureTest {
  public:
   DartIsolateTest() : FixtureTest(kernel_file_name, elf_file_name, "") {}
+
+  void OverrideDartPluginRegistrant(const std::string& override_value) {
+    dart_plugin_registrant_library_ = override_value;
+    dart_plugin_registrant_library_override =
+        dart_plugin_registrant_library_.c_str();
+  }
+
+  void SetUp() override {
+    std::string source_path = GetSourcePath();
+    if (source_path[0] != '/') {
+      // On windows we need an extra '/' prefix.
+      source_path = "/" + source_path;
+    }
+    std::string registrant_uri = std::string("file://") + source_path +
+                                 "flutter/runtime/fixtures/dart_tool/"
+                                 "flutter_build/dart_plugin_registrant.dart";
+    OverrideDartPluginRegistrant(registrant_uri);
+  }
+
+  void TearDown() override {
+    dart_plugin_registrant_library_override = nullptr;
+  }
+
+  std::string dart_plugin_registrant_library_;
 };
 
 TEST_F(DartIsolateTest, DartPluginRegistrantIsPresent) {

runtime/fixtures/dart_tool/flutter_build/dart_plugin_registrant.dart

@@ -4,6 +4,7 @@
 
 import 'dart:isolate';
 import 'dart:ui';
+import 'dart:io' show Platform;
 
 void passMessage(String message) native 'PassMessage';
 

testing/testing.gni

@@ -27,11 +27,13 @@ template("fixtures_location") {
 
   location_path = rebase_path(invoker.assets_dir)
   testing_assets_path = rebase_path("$root_out_dir/gen/flutter/testing/assets")
+  source_path = rebase_path("//")
 
   # Array of source lines. We use a list to ensure a trailing newline is
   # emitted by write_file() to comply with -Wnewline-eof.
   location_source = [
     "namespace flutter { namespace testing { ",
+    "const char* GetSourcePath() {return \"$source_path\";} ",
     "const char* GetFixturesPath() {return \"$location_path\";} ",
     "const char* GetTestingAssetsPath() {return \"$testing_assets_path\";} ",
     "}}",

testing/testing.h

@@ -16,6 +16,8 @@
 namespace flutter {
 namespace testing {
 
+const char* GetSourcePath();
+
 //------------------------------------------------------------------------------
 /// @brief      Returns the directory containing the test fixture for the target
 ///             if this target has fixtures configured. If there are no