Update C# FeatureSetDescriptor to use auto-generated source of truth.

PiperOrigin-RevId: 692879910

csharp/BUILD.bazel

@@ -5,6 +5,8 @@
 load("@rules_pkg//pkg:mappings.bzl", "pkg_files", "strip_prefix")
 load("//build_defs:internal_shell.bzl", "inline_sh_test")
 load("//conformance:defs.bzl", "conformance_test")
+load("//editions:defaults.bzl", "compile_edition_defaults", "embed_edition_defaults")
+load("//upb/cmake:build_defs.bzl", "staleness_test")
 
 ################################################################################
 # Tests
@@ -114,3 +116,34 @@ sh_binary(
     srcs = ["build_release.sh"],
     args = ["$(location build_release.sh)"],
 )
+
+################################################################################
+# Generated edition defaults (and staleness test)
+################################################################################
+
+compile_edition_defaults(
+    name = "csharp_edition_defaults",
+    srcs = [
+        "//:descriptor_proto",
+    ],
+    maximum_edition = "2023",
+    minimum_edition = "PROTO2",
+)
+
+# TODO Make bazel tests use this output instead of the checked-in one
+embed_edition_defaults(
+    name = "embedded_csharp_edition_defaults_generate",
+    defaults = "csharp_edition_defaults",
+    encoding = "base64",
+    output = "generated/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs",
+    placeholder = "DEFAULTS_VALUE",
+    template = "src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs.template",
+)
+
+staleness_test(
+    name = "generated_csharp_defaults_staleness_test",
+    outs = ["src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs"],
+    generated_pattern = "generated/%s",
+    tags = ["manual"],
+    target_files = ["src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs"],
+)

csharp/src/Google.Protobuf.Test/Reflection/FeatureSetDescriptorTest.cs

@@ -10,33 +10,59 @@
 using Google.Protobuf.Reflection;
 using NUnit.Framework;
 using System;
-using System.Linq;
+using static Google.Protobuf.Reflection.FeatureSet.Types;
 
 namespace Google.Protobuf.Test.Reflection;
 
 public class FeatureSetDescriptorTest
 {
-    // Canonical serialized form of the edition defaults, generated by embed_edition_defaults.
-    // TODO: Update this automatically.
-    private const string DefaultsBase64 =
-        "ChMY5gciDAgBEAIYAiADKAEwAioAChMY5wciDAgCEAEYASACKAEwASoAChMY6AciDAgBEAEYASACKAEwASoAIOYHKOgH";
+    // Just selectively test a couple of hard-coded examples. This isn't meant to be exhaustive,
+    // and we don't expect to add new tests for later editions unless there's a production code change.
 
     [Test]
-    [TestCase(Edition.Proto2)]
-    [TestCase(Edition.Proto3)]
-    [TestCase(Edition._2023)]
-    public void DefaultsMatchCanonicalSerializedForm(Edition edition)
+    public void Proto2Defaults()
     {
-        var canonicalDefaults = FeatureSetDefaults.Parser
-          .WithDiscardUnknownFields(true) // Discard language-specific extensions.
-          .ParseFrom(Convert.FromBase64String(DefaultsBase64));
-        var canonicalEditionDefaults = new FeatureSet();
-        canonicalEditionDefaults.MergeFrom(
-            canonicalDefaults.Defaults.Single(def => def.Edition == edition).FixedFeatures);
-        canonicalEditionDefaults.MergeFrom(
-            canonicalDefaults.Defaults.Single(def => def.Edition == edition).OverridableFeatures);
-        var candidateEditionDefaults = FeatureSetDescriptor.GetEditionDefaults(edition).Proto;
+        var expectedDefaults = new FeatureSet
+        {
+            EnumType = EnumType.Closed,
+            FieldPresence = FieldPresence.Explicit,
+            JsonFormat = JsonFormat.LegacyBestEffort,
+            MessageEncoding = MessageEncoding.LengthPrefixed,
+            RepeatedFieldEncoding = RepeatedFieldEncoding.Expanded,
+            Utf8Validation = Utf8Validation.None,
+        };
+        var actualDefaults = FeatureSetDescriptor.GetEditionDefaults(Edition.Proto2).Proto;
+        Assert.AreEqual(expectedDefaults, actualDefaults);
+    }
+
+    [Test]
+    public void Proto3Defaults()
+    {
+        var expectedDefaults = new FeatureSet
+        {
+            EnumType = EnumType.Open,
+            FieldPresence = FieldPresence.Implicit,
+            JsonFormat = JsonFormat.Allow,
+            MessageEncoding = MessageEncoding.LengthPrefixed,
+            RepeatedFieldEncoding = RepeatedFieldEncoding.Packed,
+            Utf8Validation = Utf8Validation.Verify,
+        };
+        var actualDefaults = FeatureSetDescriptor.GetEditionDefaults(Edition.Proto3).Proto;
+        Assert.AreEqual(expectedDefaults, actualDefaults);
+    }
+
+    [Test]
+    public void MaxSupportedEdition()
+    {
+        // This should be the last piece of code to be changed when updating the C# runtime to support
+        // a new edition. It should only be changed when you're sure that all the features in the new
+        // edition are supported. Just changing the configuration for feature set default generation
+        // will *advertise* that we support the new edition, but that isn't sufficient.
+        Edition maxSupportedEdition = Edition._2023;
 
-        Assert.AreEqual(canonicalEditionDefaults, candidateEditionDefaults);
+        // These lines should not need to be changed.
+        FeatureSetDescriptor.GetEditionDefaults(maxSupportedEdition);
+        Edition invalidEdition = (Edition) (maxSupportedEdition + 1);
+        Assert.Throws<ArgumentOutOfRangeException>(() => FeatureSetDescriptor.GetEditionDefaults(invalidEdition));
     }
 }

csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.cs

@@ -9,6 +9,8 @@
 
 using System;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
 using static Google.Protobuf.Reflection.FeatureSet.Types;
 
 namespace Google.Protobuf.Reflection;
@@ -22,52 +24,55 @@ namespace Google.Protobuf.Reflection;
 /// If either of those features are ever implemented in this runtime,
 /// the feature settings will be exposed as properties in this class.
 /// </remarks>
-internal sealed class FeatureSetDescriptor
+internal sealed partial class FeatureSetDescriptor
 {
     private static readonly ConcurrentDictionary<FeatureSet, FeatureSetDescriptor> cache = new();
 
-    // Note: this approach is deliberately chosen to circumvent bootstrapping issues.
-    // This can still be tested using the binary representation.
-    // TODO: Generate this code (as a partial class) from the binary representation.
-    private static readonly FeatureSetDescriptor edition2023Defaults = new FeatureSetDescriptor(
-        new FeatureSet
-        {
-            EnumType = EnumType.Open,
-            FieldPresence = FieldPresence.Explicit,
-            JsonFormat = JsonFormat.Allow,
-            MessageEncoding = MessageEncoding.LengthPrefixed,
-            RepeatedFieldEncoding = RepeatedFieldEncoding.Packed,
-            Utf8Validation = Utf8Validation.Verify,
-        });
-    private static readonly FeatureSetDescriptor proto2Defaults = new FeatureSetDescriptor(
-        new FeatureSet
+    private static readonly IReadOnlyDictionary<Edition, FeatureSetDescriptor> descriptorsByEdition = BuildEditionDefaults();
+
+    // Note: if the debugger is set to break within this code, various type initializers will fail
+    // as the debugger will try to call ToString() on messages, requiring descriptors to be accessed etc.
+    // There's a possible workaround of using a hard-coded bootstrapping FeatureSetDescriptor to be returned
+    // by GetEditionDefaults if descriptorsByEdition is null, but it's ugly and likely just pushes the problem
+    // elsewhere. Normal debugging sessions (where the initial bootstrapping code doesn't hit any breakpoints)
+    // do not cause any problems.
+    private static IReadOnlyDictionary<Edition, FeatureSetDescriptor> BuildEditionDefaults()
+    {
+        var featureSetDefaults = FeatureSetDefaults.Parser.ParseFrom(Convert.FromBase64String(DefaultsBase64));
+        var ret = new Dictionary<Edition, FeatureSetDescriptor>();
+
+        // Note: Enum.GetValues<TEnum> isn't available until .NET 5. It's not worth making this conditional
+        // based on that.
+        var supportedEditions = ((Edition[]) Enum.GetValues(typeof(Edition)))
+            .OrderBy(x => x)
+            .Where(e => e >= featureSetDefaults.MinimumEdition && e <= featureSetDefaults.MaximumEdition);
+
+        // We assume the embedded defaults will always contain "legacy".
+        var currentDescriptor = MaybeCreateDescriptor(Edition.Legacy);
+        foreach (var edition in supportedEditions)
         {
-            EnumType = EnumType.Closed,
-            FieldPresence = FieldPresence.Explicit,
-            JsonFormat = JsonFormat.LegacyBestEffort,
-            MessageEncoding = MessageEncoding.LengthPrefixed,
-            RepeatedFieldEncoding = RepeatedFieldEncoding.Expanded,
-            Utf8Validation = Utf8Validation.None,
-        });
-    private static readonly FeatureSetDescriptor proto3Defaults = new FeatureSetDescriptor(
-        new FeatureSet
+            currentDescriptor = MaybeCreateDescriptor(edition) ?? currentDescriptor;
+            ret[edition] = currentDescriptor;
+        }
+        return ret;
+
+        FeatureSetDescriptor MaybeCreateDescriptor(Edition edition)
         {
-            EnumType = EnumType.Open,
-            FieldPresence = FieldPresence.Implicit,
-            JsonFormat = JsonFormat.Allow,
-            MessageEncoding = MessageEncoding.LengthPrefixed,
-            RepeatedFieldEncoding = RepeatedFieldEncoding.Packed,
-            Utf8Validation = Utf8Validation.Verify,
-        });
+            var editionDefaults = featureSetDefaults.Defaults.SingleOrDefault(d => d.Edition == edition);
+            if (editionDefaults is null)
+            {
+                return null;
+            }
+            var proto = new FeatureSet();
+            proto.MergeFrom(editionDefaults.FixedFeatures);
+            proto.MergeFrom(editionDefaults.OverridableFeatures);
+            return new FeatureSetDescriptor(proto);
+        }
+    }
 
     internal static FeatureSetDescriptor GetEditionDefaults(Edition edition) =>
-        edition switch
-        {
-            Edition.Proto2 => proto2Defaults,
-            Edition.Proto3 => proto3Defaults,
-            Edition._2023 => edition2023Defaults,
-            _ => throw new ArgumentOutOfRangeException($"Unsupported edition: {edition}")
-        };
+        descriptorsByEdition.TryGetValue(edition, out var defaults) ? defaults
+        : throw new ArgumentOutOfRangeException($"Unsupported edition: {edition}");
 
     // Visible for testing. The underlying feature set proto, usually derived during
     // feature resolution.

csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs.template

@@ -0,0 +1,17 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+#endregion
+
+namespace Google.Protobuf.Reflection;
+
+internal sealed partial class FeatureSetDescriptor
+{
+    // Canonical serialized form of the edition defaults, generated by embed_edition_defaults.
+    private const string DefaultsBase64 =
+        "DEFAULTS_VALUE";
+}

regenerate_stale_files.sh

@@ -13,6 +13,7 @@ cd $(dirname -- "$0")
 readonly BazelBin="${BAZEL:-bazel} ${BAZEL_STARTUP_FLAGS}"
 
 STALENESS_TESTS=(
+  "csharp:generated_csharp_defaults_staleness_test"
   "java/core:generated_java_defaults_staleness_test"
   "upb/reflection:bootstrap_upb_defaults_staleness_test"
   "cmake:test_dependencies_staleness"