feat: dynamically determine protobuf version in build.gradle (#1753)

* feat: dynamically determine protobuf version in build.gradle

* add code comment

* add a method to sync versions from googleapis

* add a seperate dict for synced version

* restore protobuf version in dependencies.properties

* add synced version after reading properties

* combine two properties

* remove protobuf version in dependencies.properties

* empty commit

* Revert "remove protobuf version in dependencies.properties"

This reverts commit 22d3d0c.

* add comment for protobuf version

* make a copy of properties

* change comment

* change comments

gax-java/dependencies.properties

@@ -23,6 +23,8 @@ version.gax_httpjson=0.114.1-SNAPSHOT
 # Versions for dependencies which actual artifacts differ between Bazel and Gradle.
 # Gradle build depends on prebuilt maven artifacts, while Bazel build depends on Bazel workspaces
 # with the sources.
+# The protobuf version is only used for generating gradle files for showcase module,
+# not for self-service clients (from googleapis project).
 version.com_google_protobuf=3.23.2
 version.google_java_format=1.15.0
 version.io_grpc=1.54.0

rules_java_gapic/java_gapic_pkg.bzl

@@ -13,14 +13,20 @@
 # limitations under the License.
 
 load("@com_google_api_gax_java_properties//:dependencies.properties.bzl", "PROPERTIES")
+load("@com_google_protobuf//:protobuf_version.bzl", "PROTOBUF_JAVA_VERSION")
 
 def _wrapPropertyNamesInBraces(properties):
     wrappedProperties = {}
     for k, v in properties.items():
         wrappedProperties["{{%s}}" % k] = v
     return wrappedProperties
 
-_PROPERTIES = _wrapPropertyNamesInBraces(PROPERTIES)
+# Before this replacement, there was a problem (e.g., b/284292352) when
+# the version of protobuf defined in googleapis is higher than protobuf
+# defined in gax-java/dependencies.properties, use this replacement to
+# sync the two versions.
+SYNCED_PROPERTIES = PROPERTIES | {"version.com_google_protobuf": PROTOBUF_JAVA_VERSION}
+_PROPERTIES = _wrapPropertyNamesInBraces(SYNCED_PROPERTIES)
 
 # ========================================================================
 # General packaging helpers.
@@ -63,7 +69,7 @@ def _gapic_pkg_tar_impl(ctx):
         for f in dep.files.to_list():
             deps.append(f)
 
-    samples =[]
+    samples = []
     for s in ctx.attr.samples:
         for f in s.files.to_list():
             samples.append(f)