more refactor fun!

functions_framework/lib/src/function_config.dart

@@ -17,8 +17,8 @@ import 'dart:io';
 import 'package:args/args.dart';
 
 import 'bad_configuration.dart';
+import 'helpers.dart';
 
-const defaultPort = 8080;
 const defaultFunctionType = FunctionType.http;
 const defaultFunctionTarget = 'function';
 
@@ -40,39 +40,22 @@ class FunctionConfig {
   final String target;
 
   FunctionConfig({
-    this.port = defaultPort,
+    this.port = defaultListenPort,
     this.functionType = defaultFunctionType,
     this.target = defaultFunctionTarget,
   });
 
   // Required per spec:
   // https://github.com/GoogleCloudPlatform/functions-framework#specification-summary
-  factory FunctionConfig.fromEnv() {
-    int port;
-
-    if (Platform.environment.containsKey('PORT')) {
-      try {
-        port = int.parse(Platform.environment['PORT']!);
-      } on FormatException catch (e) {
-        throw BadConfigurationException(
-          'Bad value for environment variable "PORT" – '
-          '"${Platform.environment['PORT']}" – ${e.message}.',
-        );
-      }
-    } else {
-      port = defaultPort;
-    }
-
-    return FunctionConfig(
-      port: port,
-      target: Platform.environment[environmentKeyFunctionTarget] ??
-          defaultFunctionTarget,
-      functionType: _parseFunctionType(
-        Platform.environment['FUNCTION_SIGNATURE_TYPE'] ??
-            _enumValue(FunctionType.http),
-      ),
-    );
-  }
+  factory FunctionConfig.fromEnv() => FunctionConfig(
+        port: listenPort(),
+        target: Platform.environment[environmentKeyFunctionTarget] ??
+            defaultFunctionTarget,
+        functionType: _parseFunctionType(
+          Platform.environment['FUNCTION_SIGNATURE_TYPE'] ??
+              _enumValue(FunctionType.http),
+        ),
+      );
 
   // Optional per spec:
   // https://github.com/GoogleCloudPlatform/functions-framework#specification-summary
@@ -121,7 +104,7 @@ class FunctionConfig {
         );
       }
     } else {
-      port = defaults?.port ?? defaultPort;
+      port = defaults?.port ?? defaultListenPort;
     }
 
     final functionTypeOptionValue = options[_functionTypeOpt] as String?;

functions_framework/lib/src/helpers.dart

@@ -12,19 +12,43 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-/// Utilities to consider pulling into a separate package.
-library functions_framework.src.helpers;
-
 import 'dart:async';
 import 'dart:io';
 
+import 'package:http/http.dart' as http;
+
+import 'bad_configuration.dart';
+
+const defaultListenPort = 8080;
+
+/// Returns the port to listen on from environment variable "PORT" or uses
+/// [defaultPort] if none is defined.
+///
+/// If the "PORT" environment variable is defined, but it cannot be parsed as a
+/// an [int], a [BadConfigurationException] is thrown.
+///
+/// See https://cloud.google.com/run/docs/reference/container-contract#port
+int listenPort({int defaultPort = defaultListenPort}) {
+  if (Platform.environment.containsKey('PORT')) {
+    try {
+      return int.parse(Platform.environment['PORT']!);
+    } on FormatException catch (e) {
+      throw BadConfigurationException(
+        'Bad value for environment variable "PORT" – '
+        '"${Platform.environment['PORT']}" – ${e.message}.',
+      );
+    }
+  } else {
+    return defaultPort;
+  }
+}
+
 /// Returns a [Future] that completes when the process receives a
 /// [ProcessSignal] requesting a shutdown.
 ///
 /// [ProcessSignal.sigint] is listened to on all platforms.
 ///
 /// [ProcessSignal.sigterm] is listened to on all platforms except Windows.
-// Copied from https://github.com/dart-lang/samples/blob/091c89c984/server/google_apis/lib/helpers.dart#L44
 Future<void> terminateRequestFuture() {
   final completer = Completer<bool>.sync();
 
@@ -58,3 +82,68 @@ Future<void> terminateRequestFuture() {
 
   return completer.future;
 }
+
+/// Returns a [Future] that completes with the
+/// [Project ID](https://cloud.google.com/resource-manager/docs/creating-managing-projects#identifying_projects)
+/// for the current Google Cloud Project.
+///
+/// First, if an environment variable with a name in
+/// [gcpProjectIdEnvironmentVariables] exists, that is returned.
+/// (The list is checked in order.) This is useful for local development.
+///
+/// If no such environment variable exists, then we assume the code is running
+/// on Google Cloud and
+/// [Project metadata](https://cloud.google.com/compute/docs/metadata/default-metadata-values#project_metadata)
+/// is queried for the Project ID.
+Future<String> currentProjectId() async {
+  for (var envKey in gcpProjectIdEnvironmentVariables) {
+    final value = Platform.environment[envKey];
+    if (value != null) return value;
+  }
+
+  const host = 'http://metadata.google.internal/';
+  final url = Uri.parse('$host/computeMetadata/v1/project/project-id');
+
+  try {
+    final response = await http.get(
+      url,
+      headers: {'Metadata-Flavor': 'Google'},
+    );
+
+    if (response.statusCode != 200) {
+      throw HttpException(
+        '${response.body} (${response.statusCode})',
+        uri: url,
+      );
+    }
+
+    return response.body;
+  } on SocketException {
+    stderr.writeln(
+      '''
+Could not connect to $host.
+If not running on Google Cloud, one of these environment variables must be set
+to the target Google Project ID:
+${gcpProjectIdEnvironmentVariables.join('\n')}
+''',
+    );
+    rethrow;
+  }
+}
+
+/// A set of typical environment variables that are likely to represent the
+/// current Google Cloud project ID.
+///
+/// For context, see:
+/// * https://cloud.google.com/functions/docs/env-var
+/// * https://cloud.google.com/compute/docs/gcloud-compute#default_project
+/// * https://github.com/GoogleContainerTools/gcp-auth-webhook/blob/08136ca171fe5713cc70ef822c911fbd3a1707f5/server.go#L38-L44
+///
+/// Note: these are ordered starting from the most current/canonical to least.
+/// (At least as could be determined at the time of writing.)
+const gcpProjectIdEnvironmentVariables = {
+  'GCP_PROJECT',
+  'GCLOUD_PROJECT',
+  'CLOUDSDK_CORE_PROJECT',
+  'GOOGLE_CLOUD_PROJECT',
+};