Use Bazel for protoc_plugin Docker build

Author: sampajano

net/grpc/gateway/docker/protoc_plugin/Dockerfile

@@ -12,56 +12,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# TODO: Migrate to be using bazel build.
 FROM grpcweb/prereqs
 
-ARG MAKEFLAGS=-j8
-ARG PROTOBUF_VERSION=v27.1
+# Build the protoc-gen-grpc-web plugin with Bazel and install it.
+# The base image already provides Bazel, protoc, and third_party deps.
 
-# Install required build tools and libraries
-RUN apt-get update && apt-get install -y \
-    cmake ninja-build \
-    pkg-config zlib1g-dev \
-    libtool autoconf automake \
-    curl unzip git build-essential && \
-    rm -rf /var/lib/apt/lists/*
-
-# Set working directory for build context
 WORKDIR /github/grpc-web
 
-# Copy full grpc-web source including third_party
-COPY . /github/grpc-web
-
-# Add this to ensure abseil-cpp is available
-RUN git clone --depth 1 https://github.com/abseil/abseil-cpp.git third_party/abseil-cpp
-
-# Clean existing Abseil install (if rebuilding)
-RUN rm -rf /usr/local/include/absl /usr/local/lib/libabsl*
-
-# Build Abseil
-WORKDIR /github/grpc-web/third_party/abseil-cpp
-RUN cmake -S . -B cmake/build \
-    -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
-    -DCMAKE_CXX_STANDARD=17 \
-    -DCMAKE_BUILD_TYPE=Release && \
-    cmake --build cmake/build --target install
-
-# Clone full Protobuf source manually (not shallow)
-WORKDIR /github/grpc-web/third_party
-RUN rm -rf protobuf && \
-    git clone https://github.com/protocolbuffers/protobuf.git && \
-    cd protobuf && \
-    git checkout ${PROTOBUF_VERSION} && \
-    git submodule update --init --recursive
-
-# Build and install Protobuf using CMake
-WORKDIR /github/grpc-web/third_party/protobuf
-RUN cmake -S . -B build \
-    -DCMAKE_BUILD_TYPE=Release \
-    -Dprotobuf_BUILD_TESTS=OFF \
-    -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
-    -DCMAKE_CXX_STANDARD=17 && \
-    cmake --build build --target install
+# Copy only files needed to build the plugin for better caching.
+COPY ./MODULE.bazel ./MODULE.bazel
+COPY ./MODULE.bazel.lock ./MODULE.bazel.lock
+COPY ./.bazelrc ./.bazelrc
+COPY ./javascript/net/grpc/web/generator javascript/net/grpc/web/generator
 
-# Optional: Debug CMake errors (if build fails)
-# RUN cat build/CMakeFiles/CMakeError.log || true
+# Build and install the plugin binary.
+RUN bazel build javascript/net/grpc/web/generator:protoc-gen-grpc-web && \
+    cp $(bazel info bazel-genfiles)/javascript/net/grpc/web/generator/protoc-gen-grpc-web \
+      /usr/local/bin/protoc-gen-grpc-web