Introduce scheduler for publishing

Author: cadivus

packages/aft/lib/src/commands/publish_command.dart

@@ -7,6 +7,7 @@ import 'dart:io';
 import 'package:aft/aft.dart';
 import 'package:aft/src/constraints_checker.dart';
 import 'package:aft/src/options/glob_options.dart';
+import 'package:aft/src/publish_scheduler.dart';
 import 'package:aws_common/aws_common.dart';
 import 'package:collection/collection.dart';
 import 'package:graphs/graphs.dart';
@@ -278,11 +279,15 @@ class PublishCommand extends AmplifyCommand with GlobOptions, PublishHelpers {
     // ordering, it is okay for later packages to fail. While this means that
     // some packages will not be published, it also means that the command
     // can be re-run to pick up where it left off.
-    for (final package in packagesNeedingPublish) {
-      await prePublish(package);
-      await publish(package);
-      await awaitPendingAnalysis(package.name);
-    }
+    final scheduler = PublishScheduler(
+      packages: packagesNeedingPublish,
+      publishPackage: (package) async {
+        await prePublish(package);
+        await publish(package);
+      },
+      command: this,
+    );
+    await scheduler.run();
 
     stdout.writeln(
       dryRun

packages/aft/lib/src/publish_scheduler.dart

@@ -0,0 +1,36 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'package:aft/aft.dart';
+
+/// A function that publishes a single package (e.g. pre-publish checks +
+/// actual publish).
+typedef PublishPackageFn = Future<void> Function(PackageInfo package);
+
+/// Schedules and executes the publishing of a list of packages in order.
+///
+/// Packages are published sequentially. After each package is published the
+/// scheduler polls for a pending analysis on pub.dev and waits until the
+/// analysis is complete before proceeding to the next package.
+class PublishScheduler {
+  PublishScheduler({
+    required List<PackageInfo> packages,
+    required PublishPackageFn publishPackage,
+    required AmplifyCommand command,
+  })  : _packages = packages,
+        _publishPackage = publishPackage,
+        _command = command;
+
+  final List<PackageInfo> _packages;
+  final PublishPackageFn _publishPackage;
+  final AmplifyCommand _command;
+
+  /// Publishes all packages sequentially, awaiting pending analysis between
+  /// each one.
+  Future<void> run() async {
+    for (final package in _packages) {
+      await _publishPackage(package);
+      await _command.awaitPendingAnalysis(package.name);
+    }
+  }
+}