feat: Allow PubUpdater to be instantiated with custom dart api base url

lib/src/pub_updater.dart

@@ -11,15 +11,24 @@ class PackageInfoRequestFailure implements Exception {}
 /// Exception thrown when the provided package information is not found.
 class PackageInfoNotFoundFailure implements Exception {}
 
+/// The pub.dev base url for querying package versions
+const _defaultBaseUrl = 'https://pub.dev/api/packages/';
+
 /// {@template pub_update}
 /// A Dart package which enables checking whether a package is up to date.
 /// {@endtemplate}
 class PubUpdater {
   /// {@macro pub_update}
-  PubUpdater([http.Client? client]) : _client = client;
-
-  /// The pub.dev base url for querying package versions
-  static const _baseUrl = 'https://pub.dev/api/packages/';
+  PubUpdater([http.Client? client, String customBaseUrl = _defaultBaseUrl])
+      : assert(
+          _isValidBaseURL(customBaseUrl),
+          '$customBaseUrl is not a valid pub api URL!',
+        ),
+        _client = client,
+        _baseUrl = customBaseUrl;
+
+  /// The base url used for querying package versions
+  final String _baseUrl;
   final http.Client? _client;
 
   Future<http.Response> _get(Uri uri) => _client?.get(uri) ?? http.get(uri);
@@ -67,4 +76,10 @@ class PubUpdater {
 
     return PackageInfo.fromJson(packageJson);
   }
+
+  /// Checks whether the passed [baseUrl] is a valid pub api url
+  static bool _isValidBaseURL(String baseUrl) {
+    return (Uri.tryParse(baseUrl)?.isAbsolute ?? false) &&
+        baseUrl.endsWith('/api/packages/');
+  }
 }

test/pub_update_test.dart

@@ -21,11 +21,16 @@ const emptyResponseBody = '{}';
 
 const command = ['dart', 'pub', 'global', 'activate', 'very_good_cli'];
 
+const customDomain = 'custom-domain.com';
+
+const customBaseUrl = 'https://$customDomain/api/packages/';
+
 void main() {
   group('PubUpdater', () {
     late Client client;
     late Response response;
     late PubUpdater pubUpdater;
+    late PubUpdater pubUpdaterWithCustomBaseURL;
     late ProcessManager processManager;
     setUpAll(() {
       registerFallbackValue(Uri());
@@ -35,6 +40,10 @@ void main() {
       client = MockClient();
       response = MockResponse();
       pubUpdater = PubUpdater(client);
+      pubUpdaterWithCustomBaseURL = PubUpdater(
+        client,
+        customBaseUrl,
+      );
       processManager = MockProcessManager();
 
       when(() => client.get(any())).thenAnswer((_) async => response);
@@ -49,8 +58,19 @@ void main() {
       expect(PubUpdater(), isNotNull);
     });
 
+    test('cannot be instantiated with incorrect custom base URL', () {
+      expect(
+        () => PubUpdater(null, 'this-is-wrong.com'),
+        throwsA(isA<AssertionError>()),
+      );
+    });
+
+    test('can be instantiated with correct custom base URL', () {
+      expect(PubUpdater(null, customBaseUrl), isNotNull);
+    });
+
     group('isUpToDate', () {
-      test('makes correct http request', () async {
+      test('makes correct http request (default)', () async {
         when(() => response.body).thenReturn(emptyResponseBody);
 
         try {
@@ -70,6 +90,26 @@ void main() {
         ).called(1);
       });
 
+      test('makes correct http request (custom domain)', () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+
+        try {
+          await pubUpdaterWithCustomBaseURL.isUpToDate(
+            packageName: 'very_good_cli',
+            currentVersion: '0.3.3',
+          );
+        } catch (_) {}
+
+        verify(
+          () => client.get(
+            Uri.https(
+              customDomain,
+              '/api/packages/very_good_cli',
+            ),
+          ),
+        ).called(1);
+      });
+
       test('returns false when currentVersion < latestVersion', () async {
         expect(
           await pubUpdater.isUpToDate(
@@ -115,7 +155,7 @@ void main() {
     });
 
     group('getLatestVersion', () {
-      test('makes correct http request', () async {
+      test('makes correct http request (default)', () async {
         when(() => response.body).thenReturn(emptyResponseBody);
 
         try {
@@ -132,6 +172,23 @@ void main() {
         ).called(1);
       });
 
+      test('makes correct http request (custom domain)', () async {
+        when(() => response.body).thenReturn(emptyResponseBody);
+
+        try {
+          await pubUpdaterWithCustomBaseURL.getLatestVersion('very_good_cli');
+        } catch (_) {}
+
+        verify(
+          () => client.get(
+            Uri.https(
+              customDomain,
+              '/api/packages/very_good_cli',
+            ),
+          ),
+        ).called(1);
+      });
+
       test('returns correct version', () async {
         when(() => response.body).thenReturn(validPackageInfoResponseBody);
         expect(