Implement Client::ListBuckets() without project. (#942)

This fixes #898. It adds a default project to ClientOptions, and
uses that project in ListBuckets. Because of the parameter packs,
the function to take an explicit project id is now called
Client::ListBucketsForProject.

* Address review comments [skip ci].

* Address review comments.

Author: coryan

google/cloud/storage/client.h

@@ -71,17 +71,48 @@ class Client {
    * @throw std::runtime_error if the operation fails.
    *
    * @par Example
-   * @snippet storage_bucket_samples.cc list buckets
+   * @snippet storage_bucket_samples.cc list buckets for project
    */
   template <typename... Options>
-  ListBucketsReader ListBuckets(std::string const& project_id,
-                                Options&&... options) {
+  ListBucketsReader ListBucketsForProject(std::string const& project_id,
+                                          Options&&... options) {
     return ListBucketsReader(raw_client_, project_id,
                              std::forward<Options>(options)...);
   }
 
   /**
-   * Fetch the bucket metadata and return it.c
+   * Fetch the list of buckets for the default project.
+   *
+   * The default project is configured in the `ClientOptions` used to construct
+   * this object. If the application does not set the project id in the
+   * `ClientOptions`, the value of the `GOOGLE_CLOUD_PROJECT` is used. If
+   * neither the environment variable is set, nor a value is set explicitly by
+   * the application this function raises an exception.
+   *
+   * @param options a list of optional query parameters and/or request headers.
+   *     Valid types for this operation include `MaxResults`, `Prefix`,
+   *     `UserProject`, and `Projection`.
+   *
+   * @throw std::logic_error if the function is called without a default
+   *     project id set.
+   * @throw std::runtime_error if the operation fails.
+   *
+   * @par Example
+   * @snippet storage_bucket_samples.cc list buckets
+   */
+  template <typename... Options>
+  ListBucketsReader ListBuckets(Options&&... options) {
+    auto const& project_id = raw_client_->client_options().project_id();
+    if (project_id.empty()) {
+      std::string msg = "Default project id not set in ";
+      msg += __func__;
+      google::cloud::internal::RaiseLogicError(msg);
+    }
+    return ListBucketsForProject(project_id, std::forward<Options>(options)...);
+  }
+
+  /**
+   * Fetch the bucket metadata and return it.
    *
    * @param bucket_name query metadata information about this bucket.
    * @param options a list of optional query parameters and/or request headers.

google/cloud/storage/client_options.cc

@@ -75,6 +75,11 @@ void ClientOptions::SetupFromEnvironment() {
       set_enable_raw_client_tracing(true);
     }
   }
+
+  char const* project_id = std::getenv("GOOGLE_CLOUD_PROJECT");
+  if (project_id != nullptr) {
+    project_id_ = project_id;
+  }
 }
 
 }  // namespace STORAGE_CLIENT_NS

google/cloud/storage/client_options.h

@@ -71,6 +71,12 @@ class ClientOptions {
     return *this;
   }
 
+  std::string const& project_id() const { return project_id_; }
+  ClientOptions& set_project_id(std::string v) {
+    project_id_ = std::move(v);
+    return *this;
+  }
+
  private:
   void SetupFromEnvironment();
 
@@ -80,6 +86,7 @@ class ClientOptions {
   std::string version_;
   bool enable_http_tracing_;
   bool enable_raw_client_tracing_;
+  std::string project_id_;
 };
 }  // namespace STORAGE_CLIENT_NS
 }  // namespace storage

google/cloud/storage/examples/run_examples_utils.sh

@@ -63,6 +63,10 @@ run_program_examples() {
     #
     case ${example} in
         list-buckets)
+            arguments=""
+            export GOOGLE_CLOUD_PROJECT="${PROJECT_ID}"
+            ;;
+        list-buckets-for-project)
             arguments="${PROJECT_ID}"
             ;;
         insert-object)
@@ -150,6 +154,7 @@ run_all_bucket_examples() {
   # test. Currently get-metadata assumes that $bucket_name is already created.
   readonly BUCKET_EXAMPLES_COMMANDS=$(tr '\n' ',' <<_EOF_
 list-buckets
+list-buckets-for-project
 get-bucket-metadata
 list-objects
 _EOF_

google/cloud/storage/examples/storage_bucket_samples.cc

@@ -48,22 +48,44 @@ void PrintUsage(int argc, char* argv[], std::string const& msg) {
 }
 
 void ListBuckets(storage::Client client, int& argc, char* argv[]) {
-  if (argc < 2) {
-    throw Usage{"list-buckets <project-id>"};
+  if (argc != 1) {
+    throw Usage{"list-buckets"};
   }
-  auto project_id = ConsumeArg(argc, argv);
   //! [list buckets] [START storage_list_buckets]
-  [](google::cloud::storage::Client client, std::string project_id) {
+  namespace gcs = google::cloud::storage;
+  [](gcs::Client client) {
     int count = 0;
-    for (auto&& meta : client.ListBuckets(project_id)) {
+    for (gcs::BucketMetadata const& meta : client.ListBuckets()) {
       std::cout << meta.name() << std::endl;
       ++count;
     }
     if (count == 0) {
-      std::cout << "No buckets in project " << project_id << std::endl;
+      std::cout << "No buckets in default project" << std::endl;
     }
   }
   //! [list buckets] [END storage_list_buckets]
+  (std::move(client));
+}
+
+void ListBucketsForProject(storage::Client client, int& argc, char* argv[]) {
+  if (argc != 2) {
+    throw Usage{"list-buckets-for-project <project-id>"};
+  }
+  auto project_id = ConsumeArg(argc, argv);
+  //! [list buckets for project]
+  namespace gcs = google::cloud::storage;
+  [](gcs::Client client, std::string project_id) {
+    int count = 0;
+    for (gcs::BucketMetadata const& meta :
+         client.ListBucketsForProject(project_id)) {
+      std::cout << meta.name() << std::endl;
+      ++count;
+    }
+    if (count == 0) {
+      std::cout << "No buckets in project " << project_id << std::endl;
+    }
+  }
+  //! [list buckets for project]
   (std::move(client), project_id);
 }
 
@@ -97,6 +119,7 @@ int main(int argc, char* argv[]) try {
   using CommandType = std::function<void(storage::Client, int&, char* [])>;
   std::map<std::string, CommandType> commands = {
       {"list-buckets", &ListBuckets},
+      {"list-buckets-for-project", &ListBucketsForProject},
       {"get-bucket-metadata", &GetBucketMetadata},
       {"list-objects", &ListObjects},
   };

google/cloud/storage/storage_client_options_test.cc

@@ -93,6 +93,24 @@ TEST_F(ClientOptionsTest, SetCredentials) {
   EXPECT_FALSE(creds.get() == other.get());
 }
 
+TEST_F(ClientOptionsTest, ProjectIdFromEnvironment) {
+  google::cloud::internal::SetEnv("GOOGLE_CLOUD_PROJECT", "test-project-id");
+  ClientOptions options(CreateInsecureCredentials());
+  EXPECT_EQ("test-project-id", options.project_id());
+}
+
+TEST_F(ClientOptionsTest, ProjectIdFromEnvironmentNotSet) {
+  google::cloud::internal::UnsetEnv("GOOGLE_CLOUD_PROJECT");
+  ClientOptions options(CreateInsecureCredentials());
+  EXPECT_EQ("", options.project_id());
+}
+
+TEST_F(ClientOptionsTest, SetProjectId) {
+  ClientOptions options(CreateInsecureCredentials());
+  options.set_project_id("test-project-id");
+  EXPECT_EQ("test-project-id", options.project_id());
+}
+
 }  // namespace
 }  // namespace STORAGE_CLIENT_NS
 }  // namespace storage

google/cloud/storage/tests/bucket_integration_test.cc

@@ -50,7 +50,7 @@ TEST_F(BucketIntegrationTest, BasicCRUD) {
   auto project_id = BucketTestEnvironment::project_id();
   Client client;
 
-  auto buckets = client.ListBuckets(project_id);
+  auto buckets = client.ListBucketsForProject(project_id);
   std::vector<BucketMetadata> initial_buckets(buckets.begin(), buckets.end());
   // Since `bucket_name` should be available, we do not expect this list to be
   // empty.