Download counts: properly handle case with non-existing package (#7973)

app/lib/service/download_counts/sync_download_counts.dart

@@ -139,8 +139,10 @@ Future<bool> processDownloadCounts(
               (await packageBackend.lookupModeratedPackage(package)) == null) {
             _logger.severe(
                 'Package $package appeared in download counts data for file '
-                '$downloadCountsFileName'
+                '$downloadCountsFileName but does not exist.\n'
                 'Error: $e');
+            hasPartiallyFailedLines = true;
+            return;
           } // else {
           // The package is either invisible, tombstoned or has no versions.
           // }

app/test/service/download_counts/download_counts_test.dart

@@ -147,6 +147,42 @@ void main() {
       expect(neonCountData, isNull);
     });
 
+    testWithProfile('with non-existing package', fn: () async {
+      final nextDate = DateTime.parse('2024-01-06');
+      final downloadCountsJsonFileNameJan6 =
+          'daily_download_counts/2024-01-06T00:00:00Z/data-000000000000.jsonl';
+      await generateFakeDownloadCounts(
+          downloadCountsJsonFileNameJan6,
+          path.join(
+              Directory.current.path,
+              'test',
+              'service',
+              'download_counts',
+              'fake_download_counts_data_non_existing_package.jsonl'));
+      bool succeeded;
+      final messages = <String>[];
+      final subscription = Logger.root.onRecord.listen((event) {
+        messages.add(event.message);
+      });
+      try {
+        succeeded = await processDownloadCounts(
+            downloadCountsJsonFileNameJan6, nextDate);
+      } finally {
+        await subscription.cancel();
+      }
+      expect(succeeded, false);
+      expect(messages.first, contains('Could not find `package "hest"`.'));
+      // We still process the lines that are possible
+      final countData =
+          await downloadCountsBackend.lookupDownloadCountData('neon');
+      expect(countData, isNotNull);
+      expect(countData!.newestDate, nextDate);
+
+      final hestCountData =
+          await downloadCountsBackend.lookupDownloadCountData('hest');
+      expect(hestCountData, isNull);
+    });
+
     testWithProfile('file not present', fn: () async {
       final nextDate = DateTime.parse('2024-01-06');
       bool succeeded;

app/test/service/download_counts/fake_download_counts_data_non_existing_package.jsonl

@@ -0,0 +1,2 @@
+{"package":"hest","total":"1","per_version":[{"version":"1.0.0","count":"1"},{"version":"1.2.0","count":"1"},{"version":"2.0.0-dev","count":"1"}]}
+{"package":"neon","total":"1","per_version":[{"version":"1.0.0","count":"1"}]}