Add protobuf 33.4.envoy module with configurable zlib dependency

[Copilot]

Protobuf's gzip_stream target hardcodes @zlib, causing header conflicts when Envoy uses @zlib-ng (GCC fails with ZLIB_VERSION redefinition under -Werror).

Changes

Created custom protobuf module at bazel-registry/modules/protobuf/33.4.envoy/:

• MODULE.bazel: Based on BCR protobuf 33.4, version set to 33.4.envoy
• patches/envoy.patch:
  • Adds label_flag for configurable zlib dependency (//:zlib)
  • Changes src/google/protobuf/io/BUILD.bazel from @zlib to //:zlib
  • Includes existing Envoy protobuf changes (protoc renaming, platform configs, warning suppressions)
• source.json: References protobuf 33.4 release with patch SHA256
• metadata.json: Module metadata

Usage

In Envoy's .bazelrc:

build --@protobuf//:zlib=@zlib-ng//:zlib-ng

The label_flag defaults to @zlib for backward compatibility but allows external override to any zlib implementation.

Original prompt

Problem

Envoy uses zlib-ng instead of standard zlib. Protobuf's gzip_stream target hardcodes @zlib as a dependency, which causes header conflicts when both @zlib and @zlib-ng headers end up in the same compilation unit (GCC fails with ZLIB_VERSION redefinition error due to -Werror).

Solution

Create a new module at bazel-registry/modules/protobuf/33.4.envoy/ that adds a label_flag for zlib so it can be configured externally.

Files to create

bazel-registry/modules/protobuf/33.4.envoy/
├── MODULE.bazel
├── source.json
└── patches/
    └── envoy.patch

Implementation Details

source.json

{
    "integrity": "sha256-aH6YpHGXO1xf1xF1DEC4uCwK3jP2Sdtl4AspDyk0Wis=",
    "strip_prefix": "protobuf-33.4",
    "url": "https://github.com/protocolbuffers/protobuf/releases/download/v33.4/protobuf-33.4.bazel.tar.gz",
    "patches": {
        "patches/envoy.patch": "sha256-CALCULATE_AFTER_CREATING_PATCH"
    },
    "patch_strip": 1
}

The integrity hash is from BCR's protobuf 33.4.

MODULE.bazel

Copy from BCR's protobuf 33.4 MODULE.bazel but:

• Change version to "33.4.envoy"
• Keep all essential bazel_dep entries including zlib
• Can omit dev_dependency sections (ruby, rust, python dev toolchains) to reduce complexity

patches/envoy.patch

CRITICAL: To create this patch correctly, you must:

1. Download/checkout the protobuf 33.4 source
2. Make the required changes to the files
3. Generate the patch using diff -ruN or git diff
4. Clean up the checkout
5. Verify the patch applies cleanly

The patch must include these changes:

1. Root BUILD.bazel - Add label_flag for zlib:

Add at the top (after existing loads):

load("@bazel_skylib//rules:common_settings.bzl", "label_flag")

Add the label_flag target:

label_flag(
    name = "zlib",
    build_setting_default = "@zlib",
    visibility = ["//visibility:public"],
)

2. Root BUILD.bazel - Existing Envoy changes:

Reference the existing patch from envoyproxy/envoy at bazel/protobuf.patch for:

• Renaming protoc cc_binary to compiled_protoc
• Adding platform config_settings (linux-aarch_64, linux-x86_64, osx-aarch_64, osx-x86_64, windows-x86_64)
• Adding protoc alias with select for prebuilt protoc binaries
• Adding protobuf_python_genproto alias

3. build_defs/cpp_opts.bzl - Add warning suppression:

Add to COPTS:

"-Wno-deprecated-declarations",

4. src/google/protobuf/io/BUILD.bazel - Use the label_flag:

Change the zlib dependency from:

"//conditions:default": ["@zlib"],

To:

"//conditions:default": ["//:zlib"],

This is the critical change that allows external configuration of which zlib to use.

Reference

The existing Envoy protobuf patch is at: https://github.com/envoyproxy/envoy/blob/main/bazel/protobuf.patch

Usage (for context, not part of this PR)

In Envoy's .bazelrc:

build --@protobuf//:zlib=@zlib-ng//:zlib-ng

Important Notes

1. DO NOT invent SHA256 hashes - Calculate the patch hash after creating the patch file
2. The patch must apply cleanly to protobuf 33.4 - Download the source and verify
3. The label_flag requires bazel_skylib - Ensure the load statement is added
4. Test the patch applies - After creating, apply it to a clean checkout to verify

This pull request was created from Copilot chat.

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