[fuchsia] Add ability to configure separate data and asset dirs (#18858)

This allows Fuchsia components executed by the Flutter runner to
specify a directory containing assets if they wish to store assets
separate from program data. This is specified in the program metadata
field within the component's specification with the new "assets"
attribute. If this attribute is absent, assets are loaded relative to
the path specified in the "data" attribute as before.

This is useful in the short term to use a location in the package where
we can store small files more efficiently. It is also potentially
useful longer term to enforce a stronger separatation between
executable program data and non-executable assets.

This commit adds some basic unit testing for the data parsing to the
flutter_runner_tests suite.

Author: jamesr

ci/licenses_golden/licenses_flutter

@@ -1101,6 +1101,7 @@ FILE: ../../../flutter/shell/platform/fuchsia/flutter/accessibility_bridge_unitt
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/collect_traces.dart
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/component.cc
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/component.h
+FILE: ../../../flutter/shell/platform/fuchsia/flutter/component_unittest.cc
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/compositor_context.cc
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/compositor_context.h
 FILE: ../../../flutter/shell/platform/fuchsia/flutter/engine.cc

shell/platform/fuchsia/flutter/BUILD.gn

@@ -271,6 +271,9 @@ executable("flutter_runner_unittests") {
     "accessibility_bridge.cc",
     "accessibility_bridge.h",
     "accessibility_bridge_unittest.cc",
+    "component.cc",
+    "component.h",
+    "component_unittest.cc",
     "flutter_runner_fakes.h",
     "flutter_runner_product_configuration.cc",
     "flutter_runner_product_configuration.h",
@@ -315,6 +318,7 @@ executable("flutter_runner_unittests") {
     "//build/fuchsia/pkg:async-loop-default",
     "//build/fuchsia/pkg:scenic_cpp",
     "//build/fuchsia/pkg:sys_cpp_testing",
+    "//flutter/common",
     "//flutter/flow",
     "//flutter/lib/ui",
     "//flutter/runtime",

shell/platform/fuchsia/flutter/component.cc

@@ -51,9 +51,33 @@ constexpr uint32_t OPEN_RIGHT_EXECUTABLE = 8u;
 namespace flutter_runner {
 
 constexpr char kDataKey[] = "data";
+constexpr char kAssetsKey[] = "assets";
 constexpr char kTmpPath[] = "/tmp";
 constexpr char kServiceRootPath[] = "/svc";
 
+// static
+void Application::ParseProgramMetadata(
+    const fidl::VectorPtr<fuchsia::sys::ProgramMetadata>& program_metadata,
+    std::string* data_path,
+    std::string* assets_path) {
+  if (!program_metadata.has_value()) {
+    return;
+  }
+  for (const auto& pg : *program_metadata) {
+    if (pg.key.compare(kDataKey) == 0) {
+      *data_path = "pkg/" + pg.value;
+    } else if (pg.key.compare(kAssetsKey) == 0) {
+      *assets_path = "pkg/" + pg.value;
+    }
+  }
+
+  // assets_path defaults to the same as data_path if omitted.
+  if (assets_path->empty()) {
+    *assets_path = *data_path;
+  }
+}
+
+// static
 ActiveApplication Application::Create(
     TerminationCallback termination_callback,
     fuchsia::sys::Package package,
@@ -149,14 +173,11 @@ Application::Application(
     settings_.dart_entrypoint_args = arguments.value();
   }
 
-  // Determine /pkg/data directory from StartupInfo.
+  // Determine where data and assets are stored within /pkg.
   std::string data_path;
-  for (size_t i = 0; i < startup_info.program_metadata->size(); ++i) {
-    auto pg = startup_info.program_metadata->at(i);
-    if (pg.key.compare(kDataKey) == 0) {
-      data_path = "pkg/" + pg.value;
-    }
-  }
+  std::string assets_path;
+  ParseProgramMetadata(startup_info.program_metadata, &data_path, &assets_path);
+
   if (data_path.empty()) {
     FML_DLOG(ERROR) << "Could not find a /pkg/data directory for "
                     << package.resolved_url;
@@ -189,11 +210,20 @@ Application::Application(
     }
   }
 
-  application_directory_.reset(fdio_ns_opendir(fdio_ns_.get()));
-  FML_DCHECK(application_directory_.is_valid());
+  {
+    fml::UniqueFD ns_fd(fdio_ns_opendir(fdio_ns_.get()));
+    FML_DCHECK(ns_fd.is_valid());
+
+    constexpr mode_t mode = O_RDONLY | O_DIRECTORY;
 
-  application_assets_directory_.reset(openat(
-      application_directory_.get(), data_path.c_str(), O_RDONLY | O_DIRECTORY));
+    application_assets_directory_.reset(
+        openat(ns_fd.get(), assets_path.c_str(), mode));
+    FML_DCHECK(application_assets_directory_.is_valid());
+
+    application_data_directory_.reset(
+        openat(ns_fd.get(), data_path.c_str(), mode));
+    FML_DCHECK(application_data_directory_.is_valid());
+  }
 
   // TODO: LaunchInfo::out.
 
@@ -294,7 +324,7 @@ Application::Application(
     std::string app_framework;
     if (dart_utils::ReadFileToString("pkg/data/runner.frameworkversion",
                                      &runner_framework) &&
-        dart_utils::ReadFileToStringAt(application_assets_directory_.get(),
+        dart_utils::ReadFileToStringAt(application_data_directory_.get(),
                                        "app.frameworkversion",
                                        &app_framework) &&
         (runner_framework.compare(app_framework) == 0)) {
@@ -509,7 +539,7 @@ void Application::AttemptVMLaunchWithCurrentSettings(
 
   std::shared_ptr<dart_utils::ElfSnapshot> snapshot =
       std::make_shared<dart_utils::ElfSnapshot>();
-  if (snapshot->Load(application_assets_directory_.get(),
+  if (snapshot->Load(application_data_directory_.get(),
                      "app_aot_snapshot.so")) {
     const uint8_t* isolate_data = snapshot->IsolateData();
     const uint8_t* isolate_instructions = snapshot->IsolateInstrs();
@@ -531,20 +561,16 @@ void Application::AttemptVMLaunchWithCurrentSettings(
                                                hold_snapshot));
   } else {
     vm_snapshot = fml::MakeRefCounted<flutter::DartSnapshot>(
-        CreateWithContentsOfFile(
-            application_assets_directory_.get() /* /pkg/data */,
-            "vm_snapshot_data.bin", false),
-        CreateWithContentsOfFile(
-            application_assets_directory_.get() /* /pkg/data */,
-            "vm_snapshot_instructions.bin", true));
+        CreateWithContentsOfFile(application_data_directory_.get(),
+                                 "vm_snapshot_data.bin", false),
+        CreateWithContentsOfFile(application_data_directory_.get(),
+                                 "vm_snapshot_instructions.bin", true));
 
     isolate_snapshot_ = fml::MakeRefCounted<flutter::DartSnapshot>(
-        CreateWithContentsOfFile(
-            application_assets_directory_.get() /* /pkg/data */,
-            "isolate_snapshot_data.bin", false),
-        CreateWithContentsOfFile(
-            application_assets_directory_.get() /* /pkg/data */,
-            "isolate_snapshot_instructions.bin", true));
+        CreateWithContentsOfFile(application_data_directory_.get(),
+                                 "isolate_snapshot_data.bin", false),
+        CreateWithContentsOfFile(application_data_directory_.get(),
+                                 "isolate_snapshot_instructions.bin", true));
   }
 
   auto vm = flutter::DartVMRef::Create(settings_,               //

shell/platform/fuchsia/flutter/component.h

@@ -70,6 +70,11 @@ class Application final : public Engine::Delegate,
   // may be collected after.
   ~Application();
 
+  static void ParseProgramMetadata(
+      const fidl::VectorPtr<fuchsia::sys::ProgramMetadata>& program_metadata,
+      std::string* data_path,
+      std::string* assets_path);
+
   const std::string& GetDebugLabel() const;
 
 #if !defined(DART_PRODUCT)
@@ -82,7 +87,7 @@ class Application final : public Engine::Delegate,
   TerminationCallback termination_callback_;
   const std::string debug_label_;
   UniqueFDIONS fdio_ns_ = UniqueFDIONSCreate();
-  fml::UniqueFD application_directory_;
+  fml::UniqueFD application_data_directory_;
   fml::UniqueFD application_assets_directory_;
 
   fidl::Binding<fuchsia::sys::ComponentController> application_controller_;

shell/platform/fuchsia/flutter/component_unittest.cc

@@ -0,0 +1,51 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/fuchsia/flutter/component.h"
+
+#include <gtest/gtest.h>
+
+namespace flutter_runner {
+namespace {
+
+TEST(Component, ParseProgramMetadata) {
+  std::string data_path;
+  std::string assets_path;
+
+  // The ProgramMetadata field may be null. We should parse this as if no
+  // fields were specified.
+  Application::ParseProgramMetadata(nullptr, &data_path, &assets_path);
+
+  EXPECT_EQ(data_path, "");
+  EXPECT_EQ(assets_path, "");
+
+  // The ProgramMetadata field may be empty. Treat this the same as null.
+  fidl::VectorPtr<fuchsia::sys::ProgramMetadata> program_metadata(size_t{0});
+
+  Application::ParseProgramMetadata(program_metadata, &data_path, &assets_path);
+
+  EXPECT_EQ(data_path, "");
+  EXPECT_EQ(assets_path, "");
+
+  // The assets_path defaults to the "data" value if unspecified
+  program_metadata = {{"data", "foobar"}};
+
+  Application::ParseProgramMetadata(program_metadata, &data_path, &assets_path);
+
+  EXPECT_EQ(data_path, "pkg/foobar");
+  EXPECT_EQ(assets_path, "pkg/foobar");
+
+  data_path = "";
+  assets_path = "";
+
+  program_metadata = {{"not_data", "foo"}, {"data", "bar"}, {"assets", "baz"}};
+
+  Application::ParseProgramMetadata(program_metadata, &data_path, &assets_path);
+
+  EXPECT_EQ(data_path, "pkg/bar");
+  EXPECT_EQ(assets_path, "pkg/baz");
+}
+
+}  // anonymous namespace
+}  // namespace flutter_runner