Set version info using info from the package context

Motivation:

The version for the package included in protoc-gen-grpc-swift is updated
manually and is currently incorrect. We can get the appropriate
information from the context provided by SwiftPM.

Modifications:

- Add a C shim module which provides a version string from the package
  context

Result:

- Version string is kept up-to-date
- Resolves #60

Author: glbrntt

Package.swift

@@ -54,12 +54,26 @@ let defaultSwiftSettings: [SwiftSetting] = [
   .enableUpcomingFeature("MemberImportVisibility"),
 ]
 
+extension Context {
+  fileprivate static var versionString: String {
+    guard let git = Self.gitInformation else { return "" }
+
+    if let tag = git.currentTag {
+      return tag
+    } else {
+      let suffix = git.hasUncommittedChanges ? " (modified)" : ""
+      return git.currentCommit + suffix
+    }
+  }
+}
+
 let targets: [Target] = [
   // protoc plugin for grpc-swift
   .executableTarget(
     name: "protoc-gen-grpc-swift",
     dependencies: [
       .target(name: "GRPCProtobufCodeGen"),
+      .target(name: "CGRPCProtobuf"),
       .product(name: "GRPCCodeGen", package: "grpc-swift"),
       .product(name: "SwiftProtobuf", package: "swift-protobuf"),
       .product(name: "SwiftProtobufPluginLibrary", package: "swift-protobuf"),
@@ -110,6 +124,13 @@ let targets: [Target] = [
     swiftSettings: defaultSwiftSettings
   ),
 
+  .target(
+    name: "CGRPCProtobuf",
+    cSettings: [
+      .define("CGRPC_GRPC_SWIFT_PROTOBUF_VERSION", to: "\"\(Context.versionString)\"")
+    ]
+  ),
+
   // Code generator build plugin
   .plugin(
     name: "GRPCProtobufGenerator",

Sources/CGRPCProtobuf/CGRPCProtobuf.c

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2025, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CGRPCProtobuf.h"
+
+const char *cgrprc_grpc_swift_protobuf_version() {
+  return CGRPC_GRPC_SWIFT_PROTOBUF_VERSION;
+}

Sources/CGRPCProtobuf/include/CGRPCProtobuf.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2025, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CGRPC_PROTOBUF_H_
+#define CGRPC_PROTOBUF_H_
+
+const char *cgrprc_grpc_swift_protobuf_version();
+
+#endif  // CGRPC_PROTOBUF_H_

Sources/protoc-gen-grpc-swift/Version.swift

@@ -14,26 +14,11 @@
  * limitations under the License.
  */
 
-internal enum Version {
-  /// The major version.
-  internal static let major = 1
-
-  /// The minor version.
-  internal static let minor = 0
-
-  /// The patch version.
-  internal static let patch = 0
-
-  /// Any additional label.
-  internal static let label = "development"
+private import CGRPCProtobuf
 
+internal enum Version {
   /// The version string.
   internal static var versionString: String {
-    let version = "\(Self.major).\(Self.minor).\(Self.patch)"
-    if Self.label.isEmpty {
-      return version
-    } else {
-      return version + "-" + Self.label
-    }
+    String(cString: cgrprc_grpc_swift_protobuf_version())
   }
 }