Teach sky_snapshot about .packages

The sky_snapshot tool now understands the --packages command-line flag.

Progress on https://github.com/flutter/flutter/issues/1351

sky/engine/tonic/parsers/BUILD.gn

+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+source_set("parsers") {
+  sources = [
+    "packages_map.cc",
+    "packages_map.h",
+  ]
+}

sky/engine/tonic/parsers/packages_map.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Spec: https://github.com/lrhn/dep-pkgspec/blob/master/DEP-pkgspec.md
+
+#include "sky/engine/tonic/parsers/packages_map.h"
+
+#include <memory>
+
+namespace tonic {
+namespace {
+
+bool isLineBreak(char c) {
+  return c == '\r' || c == '\n';
+}
+
+}  // namespace
+
+PackagesMap::PackagesMap() {
+}
+
+PackagesMap::~PackagesMap() {
+}
+
+bool PackagesMap::Parse(const std::string& source, std::string* error) {
+  map_.clear();
+  const auto end = source.end();
+  for (auto it = source.begin(); it != end; ++it) {
+    const char c = *it;
+
+    // Skip blank lines.
+    if (isLineBreak(c))
+      continue;
+
+    // Skip comments.
+    if (c == '#') {
+      while (it != end && !isLineBreak(*it))
+        ++it;
+      continue;
+    }
+
+    if (c == ':') {
+      map_.clear();
+      *error = "Packages file contains a line that begins with ':'.";
+      return false;
+    }
+
+    auto package_name_begin = it;
+    auto package_name_end = end;
+    bool found_separator = false;
+    for ( ; it != end; ++it) {
+      const char c = *it;
+      if (c == ':' && !found_separator) {
+        found_separator = true;
+        package_name_end = it;
+        continue;
+      }
+      if (isLineBreak(c))
+        break;
+    }
+
+    if (!found_separator) {
+      map_.clear();
+      *error = "Packages file contains non-comment line that lacks a ':'.";
+      return false;
+    }
+
+    std::string package_name(package_name_begin, package_name_end);
+    std::string package_path(package_name_end + 1, it);
+
+    auto result = map_.emplace(package_name, package_path);
+    if (!result.second) {
+      map_.clear();
+      *error = std::string(
+          "Packages file contains multiple entries for package '") +
+          package_name + "'.";
+      return false;
+    }
+  }
+
+  return true;
+}
+
+std::string PackagesMap::Resolve(const std::string& package_name) {
+  return map_[package_name];
+}
+
+}  // namespace tonic

sky/engine/tonic/parsers/packages_map.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SKY_ENGINE_TONIC_PARSERS_PACKAGES_MAP_H_
+#define SKY_ENGINE_TONIC_PARSERS_PACKAGES_MAP_H_
+
+#include <unordered_map>
+#include <string>
+
+namespace tonic {
+
+class PackagesMap {
+ public:
+  PackagesMap();
+  ~PackagesMap();
+
+  bool Parse(const std::string& source, std::string* error);
+  std::string Resolve(const std::string& package_name);
+
+ private:
+  std::unordered_map<std::string, std::string> map_;
+};
+
+}  // namespace tonic
+
+#endif  // SKY_ENGINE_TONIC_PARSERS_PACKAGES_MAP_H_

sky/tools/sky_snapshot/BUILD.gn

@@ -21,6 +21,7 @@ executable("sky_snapshot") {
     "//dart/runtime/vm:libdart_platform",
     "//dart/runtime:libdart",
     "//sky/engine/bindings:snapshot_cc",
+    "//sky/engine/tonic/parsers",
     "//third_party/zlib",
   ]
 

sky/tools/sky_snapshot/loader.cc

@@ -12,6 +12,7 @@
 #include "sky/tools/sky_snapshot/logging.h"
 #include "sky/tools/sky_snapshot/scope.h"
 #include "sky/tools/sky_snapshot/switches.h"
+#include "sky/engine/tonic/parsers/packages_map.h"
 
 namespace {
 
@@ -34,7 +35,9 @@ base::FilePath SimplifyPath(const base::FilePath& path) {
 
 class Loader {
  public:
-  Loader(const base::FilePath& package_root);
+  Loader();
+
+  void LoadPackagesMap(const base::FilePath& packages);
 
   const std::set<std::string>& dependencies() const { return dependencies_; }
 
@@ -44,20 +47,60 @@ class Loader {
   Dart_Handle Import(Dart_Handle url);
   Dart_Handle Source(Dart_Handle library, Dart_Handle url);
 
+  void set_package_root(const base::FilePath& package_root) {
+    package_root_ = package_root;
+  }
+
  private:
   std::set<std::string> dependencies_;
+  base::FilePath packages_;
   base::FilePath package_root_;
+  std::unique_ptr<tonic::PackagesMap> packages_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Loader);
 };
 
-Loader::Loader(const base::FilePath& package_root)
-    : package_root_(package_root) {
+Loader::Loader() {
+}
+
+void Loader::LoadPackagesMap(const base::FilePath& packages) {
+  packages_ = base::MakeAbsoluteFilePath(packages);
+  dependencies_.insert(packages_.AsUTF8Unsafe());
+  std::string packages_source;
+  if (!base::ReadFileToString(packages, &packages_source)) {
+    fprintf(stderr, "error: Unable to load .packages file '%s'.\n",
+        packages.AsUTF8Unsafe().c_str());
+    exit(1);
+  }
+  packages_map_.reset(new tonic::PackagesMap());
+  std::string error;
+  if (!packages_map_->Parse(packages_source, &error)) {
+    fprintf(stderr, "error: Unable to parse .packages file '%s'.\n%s\n",
+        packages.AsUTF8Unsafe().c_str(), error.c_str());
+    exit(1);
+  }
 }
 
 std::string Loader::CanonicalizePackageURL(std::string url) {
   DCHECK(base::StartsWithASCII(url, "package:", true));
   base::ReplaceFirstSubstringAfterOffset(&url, 0, "package:", "");
+  if (packages_map_) {
+    size_t slash = url.find('/');
+    if (slash == std::string::npos)
+      return std::string();
+    std::string package = url.substr(0, slash);
+    std::string library_path = url.substr(slash + 1);
+    std::string package_path = packages_map_->Resolve(package);
+    if (package_path.empty())
+      return std::string();
+    if (base::StartsWithASCII(package_path, "file://", true)) {
+      base::ReplaceFirstSubstringAfterOffset(&package_path, 0, "file://", "");
+      return package_path + library_path;
+    } else {
+      auto path = packages_.DirName().Append(package_path).Append(library_path);
+      return SimplifyPath(path).AsUTF8Unsafe();
+    }
+  }
   return package_root_.Append(url).AsUTF8Unsafe();
 }
 
@@ -103,10 +146,18 @@ Loader* g_loader = nullptr;
 Loader& GetLoader() {
   if (!g_loader) {
     base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
-    CHECK(command_line.HasSwitch(switches::kPackageRoot))
-        << "Need --package-root";
-    g_loader =
-        new Loader(command_line.GetSwitchValuePath(switches::kPackageRoot));
+    g_loader = new Loader();
+    if (command_line.HasSwitch(switches::kPackages)) {
+      g_loader->LoadPackagesMap(
+          command_line.GetSwitchValuePath(switches::kPackages));
+
+    } else if (command_line.HasSwitch(switches::kPackageRoot)) {
+      g_loader->set_package_root(
+          command_line.GetSwitchValuePath(switches::kPackageRoot));
+    } else {
+      fprintf(stderr, "error: Need either --packages or --package-root.\n");
+      exit(1);
+    }
   }
   return *g_loader;
 }

sky/tools/sky_snapshot/main.cc

@@ -19,10 +19,15 @@
 #include "sky/tools/sky_snapshot/vm.h"
 
 void Usage() {
-  std::cerr << "Usage: sky_snapshot"
-            << " --" << switches::kPackageRoot << " --" << switches::kSnapshot
-            << " --" << switches::kDepfile << " --" << switches::kBuildOutput
-            << " <lib/main.dart>" << std::endl;
+  std::cerr << R"USAGE(usage: sky_snapshot --packages=PACKAGES --snapshot=SNAPSHOT_BLOB <lib/main.dart>
+       [ --depfile=DEPS_FILE ] [ --build-output=BUILD_OUTPUT ] [ --help ]
+
+ * PACKAGES is the '.packages' file that defines where to find Dart packages.
+ * SNAPSHOT_BLOB is the file to write the snapshot into.
+ * DEPS_FILE is an optional '.d' file to depedendency information into.
+ * BUILD_OUTPUT optionally overrides the target name used in the DEPS_FILE.
+   (The default is SNAPSHOT_BLOB.)
+)USAGE";
 }
 
 void WriteSnapshot(base::FilePath path) {
@@ -68,6 +73,11 @@ int main(int argc, const char* argv[]) {
     return 0;
   }
 
+  if (!command_line.HasSwitch(switches::kSnapshot)) {
+    fprintf(stderr, "error: Need --snapshot.\n");
+    exit(1);
+  }
+
   InitDartVM();
   Dart_Isolate isolate = CreateDartIsolate();
   CHECK(isolate);
@@ -81,7 +91,7 @@ int main(int argc, const char* argv[]) {
 
   CHECK(!LogIfError(Dart_FinalizeLoading(true)));
 
-  CHECK(command_line.HasSwitch(switches::kSnapshot)) << "Need --snapshot";
+  CHECK(command_line.HasSwitch(switches::kSnapshot));
   WriteSnapshot(command_line.GetSwitchValuePath(switches::kSnapshot));
 
   if (command_line.HasSwitch(switches::kDepfile)) {

sky/tools/sky_snapshot/switches.cc

@@ -9,6 +9,7 @@ namespace switches {
 const char kBuildOutput[] = "build-output";
 const char kDepfile[] = "depfile";
 const char kHelp[] = "help";
+const char kPackages[] = "packages";
 const char kPackageRoot[] = "package-root";
 const char kSnapshot[] = "snapshot";
 

sky/tools/sky_snapshot/switches.h

@@ -10,6 +10,7 @@ namespace switches {
 extern const char kBuildOutput[];
 extern const char kDepfile[];
 extern const char kHelp[];
+extern const char kPackages[];
 extern const char kPackageRoot[];
 extern const char kSnapshot[];