Fine. Verify RequirementsManifest serialization round-trip.

Add `assertSerialization()` to `RequirementsManifest` to perform a
byte-for-byte round trip (write -> read -> write) and ensure a canonical
binary form.

Insert debug assertions in the analysis driver and library context to
validate manifests after updates when fine-grained dependencies are
used.

Import `dart:typed_data` and `package:collection/collection.dart` for
serialization buffers and byte list equality.

Motivation: enforce deterministic encoding to stabilize caches and
dependency signatures. No effect in release builds (asserts stripped).

Change-Id: I1f3b6342df8688c7cae00cf61634efe0cfd7c44a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/444500
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -1383,6 +1383,7 @@ class AnalysisDriver {
         }
 
         if (withFineDependencies) {
+          assert(requirements!.assertSerialization());
           globalResultRequirements = null;
         }
 

pkg/analyzer/lib/src/dart/analysis/library_context.dart

@@ -298,6 +298,7 @@ class LibraryContext {
           );
           globalResultRequirements = null;
           requirements.removeReqForLibs(cycle.libraryUris);
+          assert(requirements.assertSerialization());
 
           bundleEntry = LinkedBundleEntry(
             apiSignature: cycle.nonTransitiveApiSignature,

pkg/analyzer/lib/src/fine/requirements.dart

@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:typed_data';
+
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/resolver/scope.dart';
@@ -13,6 +15,7 @@ import 'package:analyzer/src/fine/requirement_failure.dart';
 import 'package:analyzer/src/summary2/data_reader.dart';
 import 'package:analyzer/src/summary2/data_writer.dart';
 import 'package:analyzer/src/summary2/linked_element_factory.dart';
+import 'package:collection/collection.dart';
 import 'package:meta/meta.dart';
 
 /// When using fine-grained dependencies, this variable might be set to
@@ -413,6 +416,31 @@ class RequirementsManifest {
     }
   }
 
+  /// Checks that this manifest can be written and read back without any
+  /// changes, and that the binary form is exactly the same each time.
+  ///
+  /// Used in `assert()` during debug runs to catch serialization issues.
+  ///
+  /// Returns `true` if everything matches. Throws [StateError] if not.
+  bool assertSerialization() {
+    Uint8List manifestAsBytes(RequirementsManifest manifest) {
+      var sink = BufferedSink();
+      manifest.write(sink);
+      return sink.takeBytes();
+    }
+
+    var bytes = manifestAsBytes(this);
+
+    var readManifest = RequirementsManifest.read(SummaryDataReader(bytes));
+    var bytes2 = manifestAsBytes(readManifest);
+
+    if (!const ListEquality<int>().equals(bytes, bytes2)) {
+      throw StateError('Requirement manifest bytes are different.');
+    }
+
+    return true;
+  }
+
   /// Returns the first unsatisfied requirement, or `null` if all requirements
   /// are satisfied.
   RequirementFailure? isSatisfied({