Remove explicit dependency on protobuf (#221)

With `--incompatible_enable_proto_toolchain_resolution`, the root module is supposed to provide a `proto_lang_toolchain` for Java, which injects the runtime. Hardcoded dependencies on the `protobuf` module would negate the benefits of supplying a toolchain with precompiled `protoc` and runtime.

Since the only used symbol from the protobuf runtime was an exception class, it has been replaced with a check for its class name. If more protobuf runtime symbols should be needed in the future, they should be obtained from a `current_java_proto_runtime` target that first looks for a `proto_lang_toolchain` for Java and only then falls back to the hardcoded reference.

3 files changed, 9 insertions, 9 deletions

diff --git a/MODULE.bazel b/MODULE.bazel
index 1217d43..d55deab 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -9,7 +9,6 @@ bazel_dep(name = "bazel_skylib", version = "1.4.2")
 bazel_dep(name = "rules_java", version = "6.3.0")
 bazel_dep(name = "rules_jvm_external", version = "5.2")
 bazel_dep(name = "rules_license", version = "0.0.7")
-bazel_dep(name = "protobuf", version = "21.7", repo_name = "com_google_protobuf")
 
 # Maven artifacts required by Stardoc; keep consistent with deps.bzl
 STARDOC_MAVEN_ARTIFACTS = [
diff --git a/src/main/java/com/google/devtools/build/skydoc/renderer/BUILD b/src/main/java/com/google/devtools/build/skydoc/renderer/BUILD
index 69a08f3..5ccec65 100644
--- a/src/main/java/com/google/devtools/build/skydoc/renderer/BUILD
+++ b/src/main/java/com/google/devtools/build/skydoc/renderer/BUILD
@@ -32,7 +32,6 @@ java_library(
     deps = [
         "//src/main/java/com/google/devtools/build/skydoc/rendering",
         "//stardoc/proto:stardoc_output_java_proto",
-        "@com_google_protobuf//:protobuf_java",
         "@stardoc_maven//:com_beust_jcommander",
         "@stardoc_maven//:com_google_guava_guava",
     ],
diff --git a/src/main/java/com/google/devtools/build/skydoc/renderer/RendererMain.java b/src/main/java/com/google/devtools/build/skydoc/renderer/RendererMain.java
index d7ececa..c021d0c 100644
--- a/src/main/java/com/google/devtools/build/skydoc/renderer/RendererMain.java
+++ b/src/main/java/com/google/devtools/build/skydoc/renderer/RendererMain.java
@@ -33,8 +33,6 @@ import com.google.devtools.build.skydoc.rendering.proto.StardocOutputProtos.Prov
 import com.google.devtools.build.skydoc.rendering.proto.StardocOutputProtos.RepositoryRuleInfo;
 import com.google.devtools.build.skydoc.rendering.proto.StardocOutputProtos.RuleInfo;
 import com.google.devtools.build.skydoc.rendering.proto.StardocOutputProtos.StarlarkFunctionInfo;
-import com.google.protobuf.ExtensionRegistry;
-import com.google.protobuf.InvalidProtocolBufferException;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.PrintWriter;
@@ -81,9 +79,7 @@ public final class RendererMain {
             write("\n");
           }
         }) {
-      ModuleInfo moduleInfo =
-          ModuleInfo.parseFrom(
-              new FileInputStream(inputPath), ExtensionRegistry.getEmptyRegistry());
+      ModuleInfo moduleInfo = ModuleInfo.parseFrom(new FileInputStream(inputPath));
 
       MarkdownRenderer renderer =
           new MarkdownRenderer(
@@ -161,8 +157,14 @@ public final class RendererMain {
         printWriter.println(renderer.renderMarkdownFooter(moduleInfo));
       }
 
-    } catch (InvalidProtocolBufferException e) {
-      throw new IllegalArgumentException("Input file is not a valid ModuleInfo proto.", e);
+    } catch (IOException e) {
+      // Avoid an explicit dependency on the Java protobuf runtime as it should be injected by the
+      // root module via a proto_lang_toolchain.
+      if (e.getClass().getName().equals("com.google.protobuf.InvalidProtocolBufferException")) {
+        throw new IllegalArgumentException("Input file is not a valid ModuleInfo proto.", e);
+      } else {
+        throw e;
+      }
     }
   }