Use TaskAborted exception to indicate that the current task is no longer expected to complete.

Author: isoos

app/lib/shared/exceptions.dart

@@ -51,6 +51,11 @@ class NotAcceptableException extends ResponseException {
       : super._(406, 'NotAcceptable', message);
 }
 
+/// Thrown when the underlying analysis task has been aborted.
+class TaskAbortedException extends ResponseException {
+  TaskAbortedException(String message) : super._(400, 'TaskAborted', message);
+}
+
 /// Thrown when request input is invalid, bad payload, wrong querystring, etc.
 class InvalidInputException extends ResponseException {
   InvalidInputException._(String message)

app/lib/task/backend.dart

@@ -686,13 +686,14 @@ class TaskBackend {
       final key = PackageState.createKey(_db, runtimeVersion, package);
       final state = await tx.lookupOrNull<PackageState>(key);
       if (state == null || state.versions![version] == null) {
-        throw NotFoundException.resource('$package/$version');
+        throw TaskAbortedException(
+            '$package/$version is no longer selected for analysis.');
       }
       final versionState = state.versions![version]!;
 
       // Check the secret token
       if (!versionState.isAuthorized(_extractBearerToken(request))) {
-        throw AuthenticationException.authenticationRequired();
+        throw TaskAbortedException('Secret token is no longer accepted.');
       }
       assert(versionState.scheduled != initialTimestamp);
       assert(versionState.instance != null);

pkg/pub_worker/lib/src/analyze.dart

@@ -92,12 +92,12 @@ Future<void> analyze(Payload payload) async {
                 'analyze.',
           );
         }
+      } on TaskAbortedException catch (e, st) {
+        _log.warning(
+            'failed to upload ${payload.package} / ${p.version}', e, st);
       } catch (e, st) {
         _log.shout(
-          'failed to process ${payload.package} / ${p.version}',
-          e,
-          st,
-        );
+            'failed to process ${payload.package} / ${p.version}', e, st);
       }
     }
   } finally {

pkg/pub_worker/lib/src/upload.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:_pub_shared/data/package_api.dart' show UploadInfo;
@@ -40,6 +41,15 @@ Future<void> upload(
         ));
       final res = await Response.fromStream(await client.send(req));
 
+      // Special case `TaskAborted` response code, it means that the analysis
+      // is no longer selected or the secret token timed out / was replaced
+      // (it may need a different analysis round).
+      if (res.statusCode == 400 &&
+          _extractExceptionCode(res) == 'TaskAborted') {
+        _log.warning(
+            'Task aborted, failed to upload: $filename, status = ${res.statusCode}');
+        throw TaskAbortedException(res.body);
+      }
       if (400 <= res.statusCode && res.statusCode < 500) {
         _log.shout('Failed to upload: $filename, status = ${res.statusCode}');
         throw UploadException(
@@ -80,3 +90,25 @@ final class UploadException implements Exception {
 final class IntermittentUploadException extends UploadException {
   IntermittentUploadException(String message) : super(message);
 }
+
+final class TaskAbortedException extends UploadException {
+  TaskAbortedException(String message) : super(message);
+}
+
+String? _extractExceptionCode(Response res) {
+  try {
+    final map = json.decode(res.body);
+    if (map is! Map) {
+      return null;
+    }
+    final error = map['error'];
+    if (error is! Map) {
+      return null;
+    }
+    final code = error['code'];
+    return code?.toString();
+  } on FormatException catch (_) {
+    // ignore
+  }
+  return null;
+}