feat: add support for bzlmod

This changeset adds support for Bzlmod, both in the sense that
Cap'n'Proto now uses Bzlmod for development dependencies, and also
in the sense that this codebase now defines a module which can be
published for Cap'n'Proto C++.

Nearly all dependencies for capnp are available on Bzlmod; the sole
exception being Brotli, which will still need to be added by
downstream projects.

New macros have been added so that Cap'n'Proto can be used in
projects downstream, either via `WORKSPACE.bazel` or Bzlmod.

- feat: add `capnp_repositories` in `defs/repositories.bzl`
- feat: add `capnp_workspace` in `defs/workspace.bzl`
- feat: add `MODULE.bazel` with dev and API dependencies
- feat: add support for `.bazelci` via presubmit config
- test: add integration test for `workspace` via bazel
- test: add integration test for bzlmod support
- feat: add bcr publishing flow (occurs on release)
- feat: add public target for runtime capnproto dependency
- docs: add doc page with instructions for use from bazel
- fix: make all capnproto sources private to this codebase
- chore: generate initial bzlmod dependency lockfile
- chore: move root `WORKSPACE` logic to `defs` calls
- chore: split `.bazelrc` into `base.bazelrc` to reuse settings
- chore: move `cc_capnp_library` to `internal`

Signed-off-by: Sam Gammon <[email protected]>

.bazelci/presubmit.yml

@@ -0,0 +1,29 @@
+---
+matrix:
+  bazel_version: ["7.0.0"]
+  platform: ["centos7", "debian10", "macos", "ubuntu2004"]
+
+validate_config: 1
+buildifier: latest
+
+tasks:
+  build:
+    working_directory: c++
+    include_json_profile:
+      - build
+      - test
+    build_targets:
+      - "//..."
+    test_targets:
+      - "//..."
+
+bcr_test_module:
+  module_path: "integration_tests/bzlmod"
+  matrix:
+    platform: ["debian10", "macos", "ubuntu2004", "centos7"]
+  tasks:
+    build_bzlmod_test:
+      name: "Build test module"
+      platform: ${{ platform }}
+      build_targets:
+        - "//:sample-bin"

.bcr/config.yml

@@ -0,0 +1,2 @@
+---
+moduleRoots: ["./c++"]

.bcr/metadata.template.json

@@ -0,0 +1,12 @@
+{
+  "homepage": "https://github.com/capnproto/capnproto",
+  "maintainers": [
+    {
+      "github": "kentonv",
+      "name": "Kenton Varda"
+    }
+  ],
+  "repository": ["github:capnproto/capnproto"],
+  "versions": [],
+  "yanked_versions": {}
+}

.bcr/presubmit.yml

@@ -0,0 +1,11 @@
+---
+bcr_test_module:
+  module_path: "integration_tests/bzlmod"
+  matrix:
+    platform: ["debian10", "macos", "ubuntu2004"]
+  tasks:
+    build_bzlmod_test:
+      name: "Build test module"
+      platform: ${{ platform }}
+      build_targets:
+        - "//:sample-bin"

.bcr/source.template.json

@@ -0,0 +1,5 @@
+{
+  "integrity": "",
+  "strip_prefix": "{REPO}-{VERSION}/c++",
+  "url": "https://github.com/{OWNER}/{REPO}/releases/download/{TAG}/capnproto-cpp-{VERSION}.tar.gz"
+}

.github/workflows/BUILD.bazel

@@ -0,0 +1,8 @@
+load("@buildifier_prebuilt//:rules.bzl", "buildifier")
+
+buildifier(
+    name = "buildifier.check",
+    exclude_patterns = ["./.git/*"],
+    lint_mode = "warn",
+    mode = "diff",
+)

.github/workflows/ci.bazelrc

@@ -0,0 +1,21 @@
+# This file contains Bazel settings to apply on CI only.
+# It is referenced with a --bazelrc option in the call to bazel in ci.yaml
+
+# Debug where options came from
+build --announce_rc
+
+# Apply CI configurations
+build --config=ci
+
+# This directory is configured in GitHub actions to be persisted between runs.
+# We do not enable the repository cache to cache downloaded external artifacts
+# as these are generally faster to download again than to fetch them from the
+# GitHub actions cache.
+build --disk_cache=~/.cache/bazel
+
+# Don't rely on test logs being easily accessible from the test runner,
+# though it makes the log noisier.
+test --test_output=errors
+
+# Allows tests to run bazelisk-in-bazel, since this is the cache folder used
+test --test_env=XDG_CACHE_HOME

.github/workflows/module.bazelci.yml

@@ -0,0 +1,29 @@
+---
+name: Bazel CI
+
+# Controls when the action will run.
+"on":
+  workflow_dispatch: {}
+
+permissions:
+  contents: read
+
+concurrency:
+  # Cancel previous actions from the same revision
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    uses: bazel-contrib/.github/.github/workflows/bazel.yaml@29e53247c6366e30acbedfc767f58f79fc05836c
+    with:
+      folders: |
+        [
+          "./c++",
+        ]
+      exclude_windows: false
+      exclude: |
+        [
+          {"bazelversion": "7.0.0", "bzlmodEnabled": true},
+          {"bazelversion": "7.0.0", "bzlmodEnabled": false}
+        ]

.github/workflows/quick-test.yml → .github/workflows/module.quick-test.yml

@@ -1,8 +1,9 @@
-# TODO(2.0): Support g++ once they fix coroutines. This also blocks MinGW and ManyLinux builds.
-
+---
+  # TODO(2.0): Support g++ once they fix coroutines. This also blocks MinGW and ManyLinux builds.
 name: Quick Tests
 
-on:
+"on":
+  workflow_dispatch: {}
   pull_request:
     paths-ignore:
     - 'doc/**'

.github/workflows/on.release.yml

@@ -0,0 +1,32 @@
+---
+name: Release
+
+"on":
+  push:
+    tags:
+      - "v*.*.*"
+
+  workflow_dispatch:
+    inputs:
+      prerelease:
+        description: Pre-release
+        type: boolean
+        default: false
+      artifact:
+        description: Artifact
+        type: string
+        default: "capnp-cpp"
+      dry:
+        description: Dry-run
+        type: boolean
+        default: false
+
+permissions:
+  contents: read
+
+jobs:
+  release:
+    name: "Release: BCR"
+    uses: bazel-contrib/.github/.github/workflows/release_ruleset.yaml@v2
+    with:
+      release_files: capnp-cpp-*.tar.gz

.github/workflows/release_prep.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+set -o errexit -o nounset -o pipefail
+
+# Set by GH actions, see
+# https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
+TAG=${GITHUB_REF_NAME}
+# The prefix is chosen to match what GitHub generates for source archives
+PREFIX="capnp-cpp-${TAG:1}"
+ARCHIVE="capnp-cpp-$TAG.tar.gz"
+git archive --format=tar --prefix=${PREFIX}/ ${TAG} | gzip > $ARCHIVE
+SHA=$(shasum -a 256 $ARCHIVE | awk '{print $1}')
+
+cat << EOF
+1. Enable with \`common --enable_bzlmod\` in \`.bazelrc\`.
+2. Add to your \`MODULE.bazel\` file:
+
+\`\`\`starlark
+bazel_dep(name = "capnp-cpp", version = "${TAG:1}")
+\`\`\`
+
+## Using WORKSPACE
+
+Paste this snippet into your `WORKSPACE.bazel` file:
+
+\`\`\`starlark
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+http_archive(
+    name = "capnp-cpp",
+    sha256 = "${SHA}",
+    strip_prefix = "${PREFIX}",
+    url = "https://github.com/capnproto/capnp-cpp/releases/download/${TAG}/${ARCHIVE}",
+)
+EOF
+
+awk 'f;/--SNIP--/{f=1}' integration_tests/workspace/WORKSPACE.bazel
+echo "\`\`\`" 

c++/.bazelrc

@@ -1,38 +1,6 @@
-common --noenable_bzlmod
-common --enable_platform_specific_config
+common --enable_bzlmod
 
-build:unix --cxxopt='-std=c++20' --host_cxxopt='-std=c++20' --force_pic --verbose_failures
-build:unix --cxxopt='-Wall' --host_cxxopt='-Wall'
-build:unix --cxxopt='-Wextra' --host_cxxopt='-Wextra'
-build:unix --cxxopt='-Wno-strict-aliasing' --host_cxxopt='-Wno-strict-aliasing'
-build:unix --cxxopt='-Wno-sign-compare' --host_cxxopt='-Wno-sign-compare'
-build:unix --cxxopt='-Wno-unused-parameter' --host_cxxopt='-Wno-unused-parameter'
-build:unix --cxxopt='-Wno-deprecated-this-capture' --host_cxxopt='-Wno-deprecated-this-capture'
-
-# I needed these magic spells to build locally with clang-11 and clang-12 on Ubuntu. clang-13 and up
-# work out-of-the-box.
-# TODO(2.0): Remove this when we support g++ again.
-build:linux --action_env=CXXFLAGS=-stdlib=libc++
-build:linux --action_env=LDFLAGS=-stdlib=libc++
-build:linux --action_env=BAZEL_CXXOPTS=-stdlib=libc++
-build:linux --action_env=BAZEL_LINKOPTS=-lc++:-lm
-
-build:linux --config=unix
-build:macos --config=unix
-
-# See https://bazel.build/configure/windows#symlink
-startup --windows_enable_symlinks
-# We use LLVM's MSVC-compatible compiler driver to compile our code on Windows
-# under Bazel. MSVC is natively supported when using CMake builds.
-build:windows --compiler=clang-cl
-
-build:windows --cxxopt='/std:c++20' --host_cxxopt='/std:c++20' --verbose_failures
-# The `/std:c++20` argument is unused during boringssl compilation and we don't
-# want a warning when compiling each file.
-build:windows --cxxopt='-Wno-unused-command-line-argument' --host_cxxopt='-Wno-unused-command-line-argument'
-# MSVC disappointingly sets __cplusplus to 199711L by default. Defining /Zc:__cplusplus makes it
-# set the correct value.
-build:windows --cxxopt='/Zc:__cplusplus' --host_cxxopt='/Zc:__cplusplus'
+import %workspace%/../tools/bazel/base.bazelrc
 
 # build with ssl, zlib and bazel by default
 build --//src/kj:openssl=True

c++/MODULE.bazel

@@ -0,0 +1,60 @@
+"Cap'n'Proto for C++"
+
+module(
+    name = "capnp-cpp",
+    version = "1.0.2",  # keep in sync with current version
+)
+
+
+##
+## Dependencies: API
+##
+
+bazel_dep(
+    name = "platforms",
+    version = "0.0.7",
+)
+bazel_dep(
+    name = "bazel_skylib",
+    version = "1.4.2",
+)
+bazel_dep(
+    name = "zlib",
+    version = "1.3",
+)
+bazel_dep(
+    name = "boringssl",
+    version = "0.0.0-20230215-5c22014",
+    repo_name = "ssl",
+)
+
+##
+## Dependencies: Development
+##
+
+bazel_dep(
+    name = "rules_license",
+    version = "0.0.7",
+    dev_dependency = True,
+)
+bazel_dep(
+    name = "rules_testing",
+    version = "0.4.0",
+    dev_dependency = True,
+)
+bazel_dep(
+    name = "aspect_bazel_lib",
+    version = "1.34.1",
+    dev_dependency = True,
+)
+bazel_dep(
+    name = "stardoc",
+    version = "0.6.2",
+    dev_dependency = True,
+    repo_name = "io_bazel_stardoc",
+)
+bazel_dep(
+    name = "buildifier_prebuilt",
+    version = "6.3.3",
+    dev_dependency = True,
+)