test(aft): Improved testing framework

Builds off `package:test_descriptor` to provide `PackageDescriptor` and `RepoDescriptor` for improved DX describing and setting up packages and repos.

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

@@ -10,19 +10,12 @@ import 'package:aft/src/changelog/printer.dart';
 import 'package:aft/src/options/git_ref_options.dart';
 import 'package:aft/src/options/glob_options.dart';
 import 'package:aft/src/repo.dart';
-import 'package:path/path.dart' as p;
 
 /// Command for bumping package versions across the repo.
 class VersionBumpCommand extends AmplifyCommand
     with GitRefOptions, GlobOptions {
   VersionBumpCommand() {
     argParser
-      ..addFlag(
-        'preview',
-        help: 'Preview version changes without applying',
-        defaultsTo: false,
-        negatable: false,
-      )
       ..addFlag(
         'yes',
         abbr: 'y',
@@ -56,8 +49,6 @@ class VersionBumpCommand extends AmplifyCommand
 
   late final bool yes = argResults!['yes'] as bool;
 
-  late final bool preview = argResults!['preview'] as bool;
-
   late final VersionBumpType? forcedBumpType = () {
     final forceBreaking = argResults!['force-breaking'] as bool;
     if (forceBreaking) return VersionBumpType.breaking;
@@ -85,40 +76,9 @@ class VersionBumpCommand extends AmplifyCommand
       changesForPackage: _changesForPackage,
       forcedBumpType: forcedBumpType,
     );
-    final changelogUpdates = repo.changelogUpdates;
-
-    final bumpedPackages = <PackageInfo>[];
-    for (final package in repo.publishablePackages()) {
-      final edits = package.pubspecInfo.pubspecYamlEditor.edits;
-      if (edits.isEmpty) {
-        continue;
-      }
-      bumpedPackages.add(package);
-      if (preview) {
-        logger.info('pubspec.yaml');
-        for (final edit in edits) {
-          final originalText = package.pubspecInfo.pubspecYaml
-              .substring(edit.offset, edit.offset + edit.length);
-          logger.info('$originalText --> ${edit.replacement}');
-        }
-      } else {
-        await File(p.join(package.path, 'pubspec.yaml'))
-            .writeAsString(package.pubspecInfo.pubspecYamlEditor.toString());
-      }
-      final changelogUpdate = changelogUpdates[package];
-      if (changelogUpdate != null && changelogUpdate.hasUpdate) {
-        if (preview) {
-          logger
-            ..info('CHANGELOG.md')
-            ..info(changelogUpdate.newText!);
-        } else {
-          await File(p.join(package.path, 'CHANGELOG.md'))
-              .writeAsString(changelogUpdate.toString());
-        }
-      }
-    }
-
-    return bumpedPackages;
+    return repo.writeChanges(
+      packages: repo.publishablePackages(),
+    );
   }
 
   @override
@@ -130,20 +90,18 @@ class VersionBumpCommand extends AmplifyCommand
 
     final bumpedPackages = await _updateVersions();
 
-    if (!preview) {
-      for (final package in bumpedPackages) {
-        // Run build_runner for packages which generate their version number.
-        final needsBuildRunner = package.pubspecInfo.pubspec.devDependencies
-            .containsKey('build_version');
-        if (!needsBuildRunner) {
-          continue;
-        }
-        await runBuildRunner(
-          package,
-          logger: logger,
-          verbose: verbose,
-        );
+    for (final package in bumpedPackages) {
+      // Run build_runner for packages which generate their version number.
+      final needsBuildRunner = package.pubspecInfo.pubspec.devDependencies
+          .containsKey('build_version');
+      if (!needsBuildRunner) {
+        continue;
       }
+      await runBuildRunner(
+        package,
+        logger: logger,
+        verbose: verbose,
+      );
     }
 
     logger.info('Version successfully bumped');

packages/aft/lib/src/config/config_loader.dart

@@ -6,6 +6,7 @@ import 'dart:io';
 
 import 'package:aft/src/config/config.dart';
 import 'package:aft/src/config/raw_config.dart';
+import 'package:aws_common/aws_common.dart';
 import 'package:collection/collection.dart';
 import 'package:path/path.dart' as p;
 import 'package:pubspec_parse/pubspec_parse.dart';
@@ -127,10 +128,30 @@ class AftConfigLoader {
         rawComponents.map((name, component) {
           final summaryPackage = switch (component.summary) {
             null => null,
-            final summary => repoPackages[summary]!,
+            final summary => switch (repoPackages[summary]) {
+                final summaryPackage? => summaryPackage,
+                // Allow missing summary package for testing
+                _ when zDebugMode => null,
+                _ => throw StateError(
+                    'Summary package "$summary" does not exist for component: '
+                    '${component.name}',
+                  ),
+              },
           };
-          final packages =
-              component.packages.map((name) => repoPackages[name]!).toList();
+          final packages = component.packages
+              .map(
+                (name) => switch (repoPackages[name]) {
+                  final package? => package,
+                  // Allow missing component package for testing
+                  _ when zDebugMode => null,
+                  _ => throw StateError(
+                      'Component package "$name" does not exist for component: '
+                      '${component.name}',
+                    ),
+                },
+              )
+              .nonNulls
+              .toList();
           final packageGraph = UnmodifiableMapView({
             for (final package in packages)
               package.name: package.pubspecInfo.pubspec.dependencies.keys

packages/aft/lib/src/repo.dart

@@ -51,6 +51,8 @@ class Repo {
 
   final GitDir git;
 
+  PackageInfo operator [](String packageName) => allPackages[packageName]!;
+
   /// All packages which can be published to `pub.dev`.
   List<PackageInfo> publishablePackages([
     Map<String, PackageInfo>? allPackages,
@@ -252,6 +254,35 @@ class Repo {
     }
   }
 
+  /// Writes all changes made by, for example, [bumpAllVersions], to disk.
+  ///
+  /// If [packages] is passed, only changes for those packages are written.
+  /// Otherwise, all repo packages are affected.
+  ///
+  /// Returns the list of packages which both had changes and were written.
+  Future<List<PackageInfo>> writeChanges({
+    List<PackageInfo>? packages,
+  }) async {
+    final affectedPackages = <PackageInfo>[];
+    for (final package in packages ?? allPackages.values.toList()) {
+      final edits = package.pubspecInfo.pubspecYamlEditor.edits;
+      // Don't write changelog updates for packages with no corresponding
+      // pubspec update.
+      if (edits.isEmpty) {
+        continue;
+      }
+      affectedPackages.add(package);
+      await File(p.join(package.path, 'pubspec.yaml'))
+          .writeAsString(package.pubspecInfo.pubspecYamlEditor.toString());
+      final changelogUpdate = changelogUpdates[package];
+      if (changelogUpdate != null && changelogUpdate.hasUpdate) {
+        await File(p.join(package.path, 'CHANGELOG.md'))
+            .writeAsString(changelogUpdate.toString());
+      }
+    }
+    return affectedPackages;
+  }
+
   /// Bumps the version and changelog in [package] and its component packages
   /// using [commit] and returns the new version.
   ///